Move the original get_draw_order code into the tree_iter module.

src/command/feed_logs/runner.rs

@@ -18,8 +18,8 @@ use crate::nix_util::RunningUpdate;
 
 pub(crate) async fn feed_logs(args: FeedLogArgs) -> Result<()> {
     let db_handle = DbHandle::new::<String>(None).await?;
-    let mut running_build = RunningUpdate::new()?;
+    // let mut running_build = RunningUpdate::new()?;
-    // let mut running_build = RunningBuild::new(&db_handle)?;
+    let mut running_build = RunningBuild::new(&db_handle)?;
     let file_stream = FileStream::new(args.input).await?;
     let mut nix_output_stream = NixOutputStream::new(file_stream);
     while let Some(message) = nix_output_stream.next().await? {

src/nix_util/activity.rs

@@ -126,26 +126,6 @@ impl Activity {
         }
     }
 
-    pub(crate) fn is_transparent(&self) -> bool {
-        match self {
-            Activity::Root(_activity_root) => true,
-            Activity::Unknown(_activity_unknown) => false,
-            Activity::CopyPath(_activity_copy_path) => false,
-            Activity::FileTransfer(_activity_file_transfer) => false,
-            Activity::Realize(_activity_realize) => true,
-            Activity::CopyPaths(_activity_copy_paths) => true,
-            Activity::Builds(_activity_builds) => true,
-            Activity::Build(_activity_build) => false,
-            Activity::OptimizeStore(_activity_optimize_store) => false,
-            Activity::VerifyPaths(_activity_verify_paths) => false,
-            Activity::Substitute(_activity_substitute) => false,
-            Activity::QueryPathInfo(_activity_query_path_info) => false,
-            Activity::PostBuildHook(_activity_post_build_hook) => false,
-            Activity::BuildWaiting(_activity_build_waiting) => true,
-            Activity::FetchTree(_activity_fetch_tree) => false,
-        }
-    }
-
     pub(crate) fn display_name(&self) -> Option<Cow<'_, str>> {
         match self {
             Activity::Root(_activity_root) => {
@@ -204,63 +184,43 @@ impl Activity {
 
     pub(crate) fn get_progress_text(&self) -> Option<Cow<'_, str>> {
         match self {
-            Activity::Root(_activity_root) => {
+            Activity::Root(_activity_root) => None,
-                // TODO
-                panic!("Attempted to get_progress_text of a root activity.");
-            }
             Activity::Unknown(_activity_unknown) => None,
-            Activity::CopyPath(activity_copy_path) => Some(Cow::Owned(format!(
+            Activity::CopyPath(activity_copy_path) => {
-                "[{}/{}]",
+                get_progress_bar(activity_copy_path.done, activity_copy_path.expected).or_else(
-                activity_copy_path.done, activity_copy_path.expected
+                    || get_progress_text(activity_copy_path.done, activity_copy_path.expected),
-            ))),
+                )
-            Activity::FileTransfer(activity_file_transfer) => Some(Cow::Owned(format!(
+            }
-                "[{}/{}]",
+            Activity::FileTransfer(activity_file_transfer) => {
-                activity_file_transfer.done, activity_file_transfer.expected
+                get_progress_bar(activity_file_transfer.done, activity_file_transfer.expected)
-            ))),
+                    .or_else(|| {
-            Activity::Realize(_activity_realize) => {
+                        get_progress_text(
-                // TODO
+                            activity_file_transfer.done,
-                panic!("Attempted to get_progress_text of a realize activity.");
+                            activity_file_transfer.expected,
+                        )
+                    })
+            }
+            Activity::Realize(_activity_realize) => None,
+            Activity::CopyPaths(activity_copy_paths) => {
+                get_progress_bar(activity_copy_paths.done, activity_copy_paths.expected).or_else(
+                    || get_progress_text(activity_copy_paths.done, activity_copy_paths.expected),
+                )
+            }
+            Activity::Builds(activity_builds) => {
+                get_progress_bar(activity_builds.done, activity_builds.expected)
+                    .or_else(|| get_progress_text(activity_builds.done, activity_builds.expected))
             }
-            Activity::CopyPaths(activity_copy_paths) => Some(Cow::Owned(format!(
-                "[{}/{}]",
-                activity_copy_paths.done, activity_copy_paths.expected
-            ))),
-            Activity::Builds(activity_builds) => Some(Cow::Owned(format!(
-                "[{}/{}]",
-                activity_builds.done, activity_builds.expected
-            ))),
             Activity::Build(activity_build) => activity_build
                 .phase
                 .as_ref()
                 .map(|phase| Cow::Owned(format!("[{}]", phase))),
-            Activity::OptimizeStore(_activity_optimize_store) => {
+            Activity::OptimizeStore(_activity_optimize_store) => None,
-                // TODO
+            Activity::VerifyPaths(_activity_verify_paths) => None,
-                panic!("Attempted to get_progress_text of a optimize store activity.");
+            Activity::Substitute(_activity_substitute) => None,
-            }
+            Activity::QueryPathInfo(_activity_query_path_info) => None,
-            Activity::VerifyPaths(_activity_verify_paths) => {
+            Activity::PostBuildHook(_activity_post_build_hook) => None,
-                // TODO
+            Activity::BuildWaiting(_activity_build_waiting) => None,
-                panic!("Attempted to get_progress_text of a verify paths activity.");
+            Activity::FetchTree(_activity_fetch_tree) => None,
-            }
-            Activity::Substitute(_activity_substitute) => {
-                // TODO
-                panic!("Attempted to get_progress_text of a substitute activity.");
-            }
-            Activity::QueryPathInfo(_activity_query_path_info) => {
-                // TODO
-                panic!("Attempted to get_progress_text of a query path info activity.");
-            }
-            Activity::PostBuildHook(_activity_post_build_hook) => {
-                // TODO
-                panic!("Attempted to get_progress_text of a post build hook activity.");
-            }
-            Activity::BuildWaiting(_activity_build_waiting) => {
-                // TODO
-                panic!("Attempted to get_progress_text of a build waiting activity.");
-            }
-            Activity::FetchTree(_activity_fetch_tree) => {
-                // TODO
-                panic!("Attempted to get_progress_text of a fetch tree activity.");
-            }
         }
     }
 
@@ -531,3 +491,35 @@ impl Default for ActivityState {
         }
     }
 }
+
+fn get_progress_bar(done: u64, expected: u64) -> Option<Cow<'static, str>> {
+    if expected == 0 {
+        return None;
+    }
+    let percent = done as f32 / expected as f32;
+    // ○◔◑◕●
+    // ○◎◉●
+    // ▁▂▃▄▅▆▇█
+    // ▏▎▍▌▋▊▉█
+    // ░▒▓█
+    //
+    // 🮷 download
+    // 🮸 upload
+    // 🮵
+    // 🮶
+    if percent < 0.33 {
+        Some(Cow::Borrowed("░"))
+    } else if percent < 0.66 {
+        Some(Cow::Borrowed("▒"))
+    } else if percent < 1.0 {
+        Some(Cow::Borrowed("▓"))
+    } else if percent >= 1.0 {
+        Some(Cow::Borrowed("█"))
+    } else {
+        None
+    }
+}
+
+fn get_progress_text(done: u64, expected: u64) -> Option<Cow<'static, str>> {
+    Some(Cow::Owned(format!("[{}/{}]", done, expected)))
+}

src/nix_util/activity_tree.rs

@@ -6,7 +6,7 @@ use std::ops::Deref;
 use super::activity::Activity;
 use super::activity::ActivityRoot;
 
-#[derive(Debug, Clone)]
+#[derive(Debug, Clone, PartialEq)]
 pub(crate) struct ActivityId {
     id: u64,
 }

src/nix_util/mod.rs

@@ -6,7 +6,6 @@ mod nix_output_stream;
 mod output_stream;
 mod running_build;
 mod running_update;
-mod transparent_iter;
 mod tree_iter;
 pub(crate) use activity_tree::ActivityIdAlreadyInTreeError;
 pub(crate) use activity_tree::ActivityIdNotInTreeError;

src/nix_util/running_build.rs

@@ -12,13 +12,16 @@ use crate::database::db_handle::DbHandle;
 use crate::nix_util::nix_output_stream::NixAction;
 use crate::nix_util::nix_output_stream::NixOutputStream;
 use crate::nix_util::output_stream::OutputStream;
-use crate::nix_util::transparent_iter::TransparentIter;
 
-use super::activity_tree::ActivityId;
+use super::activity::Activity;
+use super::activity_tree::ActivityTree;
 use super::activity_tree::ActivityTreeEntry;
 use super::activity_tree_stream::ActivityTreeStream;
 use super::nix_output_stream::ActivityResultMessage;
 use super::nix_output_stream::NixMessage;
+use super::tree_iter::DrawDagEntry;
+use super::tree_iter::ReverseTreeIter;
+use super::tree_iter::get_draw_order;
 
 pub(crate) struct RunningBuild<'db> {
     db_handle: &'db DbHandle,
@@ -159,143 +162,83 @@ impl<'db> RunningBuild<'db> {
     }
 
     fn print_current_status(&mut self) -> () {
-        let mut tree = String::new();
+        // let draw_order = get_draw_order(self.activity_tree.get_tree());
-        let draw_order = self.get_draw_order();
+        let draw_order = ReverseTreeIter::new(
-        for dag_entry in draw_order {
+            self.activity_tree.get_tree(),
-            let leading_bars = {
+            None,
-                let mut leading_bars = String::with_capacity(3 * dag_entry.depth.len());
+            is_match_predicate,
-                for leading_bar in dag_entry
+            is_transparent_predicate,
-                    .depth
+            is_alive_predicate,
-                    .iter()
+        )
-                    .map(|depth| if *depth { "𜹈  " } else { "   " })
+        .get_draw_order();
-                {
+
-                    leading_bars.push_str(leading_bar);
+        print_dag(self.activity_tree.get_tree(), draw_order);
-                }
-                leading_bars
-            };
-            let branch = if dag_entry.has_later_siblings {
-                "𜸨"
-            } else {
-                "𜸛"
-            };
-            let activity = self.activity_tree.get_tree().get(&dag_entry.activity_id);
-            let display_name = activity
-                .get_activity()
-                .display_name()
-                .expect("Currently we always return a display name.");
-            let progress_text = activity.get_activity().get_progress_text();
-            let (progress, progress_sep) = match progress_text {
-                Some(text) => (text, " "),
-                None => (Cow::Borrowed(""), ""),
-            };
-            tree += &format!("{leading_bars}{branch}𜸟 {progress}{progress_sep}{display_name}\n");
-        }
-        if tree.is_empty() {
-            println!("No active activities.");
-        } else {
-            print!("\n{}\n", tree);
-        }
         self.last_announce = Some(Instant::now());
     }
-
-    fn get_draw_order(&self) -> Vec<DrawDagEntry> {
-        let mut draw_order: Vec<DrawDagEntry> = Vec::new();
-        let mut stack: Vec<DrawStackEntry> = self
-            .get_children_in_order(self.activity_tree.get_tree().get_root_id())
-            .filter_map(|child| {
-                if child.get_activity().is_active() {
-                    Some(DrawStackEntry::HasNotVisitedChildren(DrawDagEntry {
-                        activity_id: child.get_activity_id().clone(),
-                        depth: Vec::new(),
-                        has_later_siblings: true,
-                    }))
-                } else {
-                    None
-                }
-            })
-            .collect();
-        if stack.len() == 0 {
-            return draw_order;
-        }
-        stack
-            .last_mut()
-            .expect("If-statement ensured this is Some()")
-            .set_no_later_siblings();
-
-        while !stack.is_empty() {
-            let current_entry = stack.pop().expect("While-loop ensured this is Some.");
-            match current_entry {
-                DrawStackEntry::HasNotVisitedChildren(draw_dag_entry) => {
-                    let current_id = draw_dag_entry.activity_id.clone();
-                    let mut current_depth = draw_dag_entry.depth.clone();
-                    current_depth.push(draw_dag_entry.has_later_siblings);
-                    stack.push(DrawStackEntry::VisitedChildren(draw_dag_entry));
-                    let children: Vec<ActivityId> = self
-                        .get_children_in_order(current_id)
-                        .filter_map(|child| {
-                            if child.get_activity().is_active() {
-                                Some(child.get_activity_id().clone())
-                            } else {
-                                None
-                            }
-                        })
-                        .collect();
-                    let has_children = !children.is_empty();
-                    stack.extend(children.into_iter().map(|child_id| {
-                        DrawStackEntry::HasNotVisitedChildren(DrawDagEntry {
-                            activity_id: child_id,
-                            depth: current_depth.clone(),
-                            has_later_siblings: true,
-                        })
-                    }));
-                    if has_children {
-                        stack
-                            .last_mut()
-                            .expect("If-statement ensured this is Some()")
-                            .set_no_later_siblings();
-                    }
-                }
-                DrawStackEntry::VisitedChildren(draw_dag_entry) => {
-                    draw_order.push(draw_dag_entry);
-                }
-            };
-        }
-        draw_order
-    }
-
-    fn get_children_in_order(
-        &self,
-        parent_id: ActivityId,
-    ) -> impl Iterator<Item = &ActivityTreeEntry> {
-        let parent = self.activity_tree.get_tree().get(&parent_id);
-        parent
-            .get_child_ids()
-            .iter()
-            .map(|child_id| self.activity_tree.get_tree().get(child_id))
-            .flat_map(|child| TransparentIter::new(self.activity_tree.get_tree(), child))
-    }
 }
 
-enum DrawStackEntry {
+pub(crate) fn print_dag(activity_tree: &ActivityTree, draw_order: Vec<DrawDagEntry>) -> () {
-    HasNotVisitedChildren(DrawDagEntry),
+    let mut tree = String::new();
-    VisitedChildren(DrawDagEntry),
+    for dag_entry in draw_order {
-}
+        let leading_bars = {
-
+            let mut leading_bars = String::with_capacity(3 * dag_entry.depth.len());
-struct DrawDagEntry {
+            for leading_bar in dag_entry
-    activity_id: ActivityId,
+                .depth
-    depth: Vec<bool>,
+                .iter()
-    has_later_siblings: bool,
+                .map(|depth| if *depth { "𜹈  " } else { "   " })
-}
+            {
-
+                leading_bars.push_str(leading_bar);
-impl DrawStackEntry {
-    fn set_no_later_siblings(&mut self) -> () {
-        match self {
-            DrawStackEntry::HasNotVisitedChildren(draw_dag_entry) => {
-                draw_dag_entry.has_later_siblings = false
-            }
-            DrawStackEntry::VisitedChildren(draw_dag_entry) => {
-                draw_dag_entry.has_later_siblings = false
             }
+            leading_bars
         };
+        let branch = if dag_entry.has_later_siblings {
+            "𜸨"
+        } else {
+            "𜸛"
+        };
+        let activity = activity_tree.get(&dag_entry.activity_id);
+        let display_name = activity
+            .get_activity()
+            .display_name()
+            .expect("Currently we always return a display name.");
+        let progress_text = activity.get_activity().get_progress_text();
+        let (progress, progress_sep) = match progress_text {
+            Some(text) => (text, " "),
+            None => (Cow::Borrowed(""), ""),
+        };
+        tree += &format!("{leading_bars}{branch}𜸟 {progress}{progress_sep}{display_name}\n");
+    }
+    if tree.is_empty() {
+        println!("No active activities.");
+    } else {
+        print!("\n{}\n", tree);
     }
 }
+
+fn is_match_predicate(_entry: &ActivityTreeEntry) -> bool {
+    true
+}
+
+pub(crate) fn is_transparent_predicate(entry: &ActivityTreeEntry) -> bool {
+    match entry.get_activity() {
+        Activity::Root(_activity_root) => true,
+        Activity::Unknown(_activity_unknown) => false,
+        Activity::CopyPath(_activity_copy_path) => false,
+        Activity::FileTransfer(_activity_file_transfer) => false,
+        Activity::Realize(_activity_realize) => true,
+        Activity::CopyPaths(_activity_copy_paths) => true,
+        Activity::Builds(_activity_builds) => true,
+        Activity::Build(_activity_build) => false,
+        Activity::OptimizeStore(_activity_optimize_store) => false,
+        Activity::VerifyPaths(_activity_verify_paths) => false,
+        Activity::Substitute(_activity_substitute) => false,
+        Activity::QueryPathInfo(_activity_query_path_info) => false,
+        Activity::PostBuildHook(_activity_post_build_hook) => false,
+        Activity::BuildWaiting(_activity_build_waiting) => true,
+        Activity::FetchTree(_activity_fetch_tree) => false,
+    }
+}
+
+fn is_alive_predicate(entry: &ActivityTreeEntry) -> bool {
+    entry.get_activity().is_active()
+}

src/nix_util/running_update.rs

@@ -1,4 +1,7 @@
 use std::borrow::Cow;
+use std::ops::Deref;
+use std::time::Duration;
+use std::time::Instant;
 
 use tokio::process::Child;
 use tracing::error;
@@ -9,21 +12,22 @@ use crate::nix_util::nix_output_stream::NixAction;
 use crate::nix_util::output_stream::OutputStream;
 use crate::nix_util::tree_iter::ForwardTreeIter;
 
-use super::activity_tree::ActivityId;
+use super::activity::Activity;
 use super::activity_tree::ActivityTreeEntry;
 use super::activity_tree_stream::ActivityTreeStream;
 use super::nix_output_stream::ActivityResultMessage;
 use super::nix_output_stream::NixMessage;
-use super::transparent_iter::TransparentIter;
 
 pub(crate) struct RunningUpdate {
     activity_tree: ActivityTreeStream,
+    last_announce: Option<Instant>,
 }
 
 impl RunningUpdate {
     pub(crate) fn new() -> Result<Self> {
         Ok(RunningUpdate {
             activity_tree: ActivityTreeStream::new(),
+            last_announce: None,
         })
     }
 
@@ -71,11 +75,11 @@ impl RunningUpdate {
                 // }
             }
             NixAction::Start(activity_start_message) => {
-                println!("START: {}", serde_json::to_string(&activity_start_message)?);
+                // println!("START: {}", serde_json::to_string(&activity_start_message)?);
                 self.print_current_status();
             }
             NixAction::Stop(stop_message) => {
-                println!("STOP: {}", serde_json::to_string(&stop_message)?);
+                // println!("STOP: {}", serde_json::to_string(&stop_message)?);
                 self.print_current_status();
             }
             NixAction::Result(activity_result_message) => {
@@ -87,19 +91,19 @@ impl RunningUpdate {
                     ActivityResultMessage::SetPhase(_activity_result_set_phase) => {}
                     ActivityResultMessage::Progress(activity_result_progress) => {
                         // if activity_result_progress.expected != 0 {
-                        println!(
+                        // println!(
-                            "PROGRESS: {}",
+                        //     "PROGRESS: {}",
-                            serde_json::to_string(&activity_result_progress)?
+                        //     serde_json::to_string(&activity_result_progress)?
-                        );
+                        // );
                         // }
                         self.maybe_print_current_status();
                     }
                     ActivityResultMessage::SetExpected(activity_result_set_expected) => {
                         // if activity_result_set_expected.expected != 0 {
-                        println!(
+                        // println!(
-                            "EXPECTED: {}",
+                        //     "EXPECTED: {}",
-                            serde_json::to_string(&activity_result_set_expected)?
+                        //     serde_json::to_string(&activity_result_set_expected)?
-                        );
+                        // );
                         // }
                         self.maybe_print_current_status();
                     }
@@ -113,24 +117,81 @@ impl RunningUpdate {
         Ok(())
     }
 
-    fn maybe_print_current_status(&mut self) -> () {}
+    fn maybe_print_current_status(&mut self) -> () {
+        let last_announce = match self.last_announce {
+            Some(instant) => instant,
+            None => {
+                // If we haven't announced before, always announce.
+                return self.print_current_status();
+            }
+        };
+
+        let now = Instant::now();
+        let time_since_last_announce = now.duration_since(last_announce);
+        if time_since_last_announce > Duration::new(5, 0) {
+            return self.print_current_status();
+        }
+    }
 
     fn print_current_status(&mut self) -> () {
         let nodes = ForwardTreeIter::new(
             self.activity_tree.get_tree(),
             None,
-            |entry| true,
+            is_match_predicate,
-            |entry| false,
+            is_transparent_predicate,
-            |entry| true,
+            is_alive_predicate,
         );
-        println!("\n\n\nvvvvvv\n\n");
+        let mut out = Vec::new();
-        for (depth, is_match, is_transparent, node) in nodes {
+        for (depth, _is_match, _is_transparent, node) in nodes {
+            let progress_text = node
+                .get_activity()
+                .get_progress_text()
+                .unwrap_or(Cow::Borrowed(""));
             let name = node
                 .get_activity()
                 .display_name()
                 .unwrap_or(Cow::Borrowed("null"));
-            println!("{depth}\t{is_match}\t{is_transparent}\t{name}");
+            out.push(format!("{depth}\t{progress_text}\t{name}"))
         }
-        println!("\n\n\n^^^^^^\n\n");
+
+        if out.is_empty() {
+            println!("No active activities.");
+        } else {
+            println!("\n");
+            for l in out {
+                println!("{l}\n");
+            }
+            println!("\n");
+        }
+        self.last_announce = Some(Instant::now());
     }
 }
+
+fn is_match_predicate(entry: &ActivityTreeEntry) -> bool {
+    entry.get_activity().get_progress_text().is_some()
+}
+
+pub(crate) fn is_transparent_predicate(entry: &ActivityTreeEntry) -> bool {
+    return false;
+    // match entry.get_activity() {
+    //     Activity::Root(_activity_root) => true,
+    //     Activity::Unknown(_activity_unknown) => false,
+    //     Activity::CopyPath(_activity_copy_path) => false,
+    //     Activity::FileTransfer(_activity_file_transfer) => false,
+    //     Activity::Realize(_activity_realize) => true,
+    //     Activity::CopyPaths(_activity_copy_paths) => true,
+    //     Activity::Builds(_activity_builds) => true,
+    //     Activity::Build(_activity_build) => false,
+    //     Activity::OptimizeStore(_activity_optimize_store) => false,
+    //     Activity::VerifyPaths(_activity_verify_paths) => false,
+    //     Activity::Substitute(_activity_substitute) => false,
+    //     Activity::QueryPathInfo(_activity_query_path_info) => false,
+    //     Activity::PostBuildHook(_activity_post_build_hook) => false,
+    //     Activity::BuildWaiting(_activity_build_waiting) => true,
+    //     Activity::FetchTree(_activity_fetch_tree) => false,
+    // }
+}
+
+fn is_alive_predicate(entry: &ActivityTreeEntry) -> bool {
+    entry.get_activity().is_active()
+}

src/nix_util/tree_iter/forward_tree_iter/benchmarks.rs

@@ -8,22 +8,22 @@ use test::Bencher;
 
 use super::*;
 
-/// Build an ActivityTree matching the description at the top of the file.
 fn build_example_tree(
     num_levels: u64,
     num_children_per_node: u64,
 ) -> Result<ActivityTree, Box<dyn std::error::Error>> {
     let mut activity_tree = ActivityTree::new();
     let mut next_index = 1;
-    let mut previous_level: Vec<u64> = Vec::new();
+    let mut previous_level: Vec<u64> = vec![0];
 
     for _ in 0..num_levels {
-        if previous_level.is_empty() {
+        let mut current_parents = Vec::new();
-            // first level, add num_children
+        std::mem::swap(&mut previous_level, &mut current_parents);
+        for parent in current_parents {
             for _ in 0..num_children_per_node {
                 activity_tree.add_activity(
                     next_index,
-                    0,
+                    parent,
                     Activity::Unknown(ActivityUnknown {
                         state: ActivityState::Stopped,
                         text: format!("N{next_index}"),
@@ -32,24 +32,6 @@ fn build_example_tree(
                 previous_level.push(next_index);
                 next_index += 1;
             }
-        } else {
-            // Subsequent levels, add num_children to each node of the previous level.
-            let mut current_parents = Vec::new();
-            std::mem::swap(&mut previous_level, &mut current_parents);
-            for parent in current_parents {
-                for _ in 0..num_children_per_node {
-                    activity_tree.add_activity(
-                        next_index,
-                        parent,
-                        Activity::Unknown(ActivityUnknown {
-                            state: ActivityState::Stopped,
-                            text: format!("N{next_index}"),
-                        }),
-                    )?;
-                    previous_level.push(next_index);
-                    next_index += 1;
-                }
-            }
         }
     }
 

src/nix_util/tree_iter/forward_tree_iter/mod.rs

@@ -43,13 +43,13 @@ use super::stack_entry::StackEntry;
 /// you would get the following output:
 ///
 /// ```text
-/// 1	False	False	A
+/// 0	False	False	A
-/// 2	True	False	B
+/// 1	True	False	B
-/// 3	False	True	D
+/// 2	False	True	D
-/// 3	True	False	E
+/// 2	True	False	E
-/// 2	False	False	H
+/// 1	False	False	H
-/// 3	False	False	I
+/// 2	False	False	I
-/// 4	True	False	J
+/// 3	True	False	J
 /// ```
 pub(crate) struct ForwardTreeIter<'tree, MP, TP, AP> {
     activity_tree: &'tree ActivityTree,
@@ -91,10 +91,15 @@ where
     fn get_next_announce<'iter>(
         &'iter mut self,
     ) -> Option<(usize, bool, bool, &'tree ActivityTreeEntry)> {
+        let origin_activity_id = *self.origin.get_activity_id().deref();
         let (activity, is_match, is_transparent) = match self
             .stack
             .iter_mut()
-            .filter(|entry| entry.should_announce() && !entry.is_announced())
+            .filter(|entry| {
+                entry.should_announce()
+                    && !entry.is_announced()
+                    && *entry.get_node().get_activity_id().deref() != origin_activity_id
+            })
             .next()
         {
             Some(entry) => {
@@ -110,7 +115,10 @@ where
 
         let depth = self
             .walk_up_stack(activity)
-            .filter(|node| !node.is_transparent())
+            .filter(|node| {
+                !node.is_transparent()
+                    && *node.get_node().get_activity_id().deref() != origin_activity_id
+            })
             .count();
 
         Some((depth, is_match, is_transparent, activity))

src/nix_util/tree_iter/forward_tree_iter/tests.rs

@@ -1,114 +1,19 @@
-use crate::nix_util::activity::Activity;
+use crate::nix_util::running_build::is_transparent_predicate;
-use crate::nix_util::activity::ActivityState;
+use crate::nix_util::tree_iter::test_util::build_example_tree;
-use crate::nix_util::activity::ActivityUnknown;
+use crate::nix_util::tree_iter::test_util::is_alive_predicate;
+use crate::nix_util::tree_iter::test_util::is_match_predicate;
 
 use super::*;
 
-/// Build an ActivityTree matching the description at the top of the file.
-fn build_example_tree() -> Result<ActivityTree, Box<dyn std::error::Error>> {
-    let mut activity_tree = ActivityTree::new();
-    activity_tree.add_activity(
-        1,
-        0,
-        Activity::Unknown(ActivityUnknown {
-            state: ActivityState::Stopped,
-            text: "A".to_owned(),
-        }),
-    )?;
-    activity_tree.add_activity(
-        2,
-        1,
-        Activity::Unknown(ActivityUnknown {
-            state: ActivityState::Stopped,
-            text: "B".to_owned(),
-        }),
-    )?;
-    activity_tree.add_activity(
-        3,
-        2,
-        Activity::Unknown(ActivityUnknown {
-            state: ActivityState::Stopped,
-            text: "C".to_owned(),
-        }),
-    )?;
-    activity_tree.add_activity(
-        4,
-        2,
-        Activity::Unknown(ActivityUnknown {
-            state: ActivityState::Stopped,
-            text: "D".to_owned(),
-        }),
-    )?;
-    activity_tree.add_activity(
-        5,
-        4,
-        Activity::Unknown(ActivityUnknown {
-            state: ActivityState::Stopped,
-            text: "E".to_owned(),
-        }),
-    )?;
-    activity_tree.add_activity(
-        6,
-        4,
-        Activity::Unknown(ActivityUnknown {
-            state: ActivityState::Stopped,
-            text: "F".to_owned(),
-        }),
-    )?;
-    activity_tree.add_activity(
-        7,
-        1,
-        Activity::Unknown(ActivityUnknown {
-            state: ActivityState::Stopped,
-            text: "G".to_owned(),
-        }),
-    )?;
-    activity_tree.add_activity(
-        8,
-        1,
-        Activity::Unknown(ActivityUnknown {
-            state: ActivityState::Stopped,
-            text: "H".to_owned(),
-        }),
-    )?;
-    activity_tree.add_activity(
-        9,
-        8,
-        Activity::Unknown(ActivityUnknown {
-            state: ActivityState::Stopped,
-            text: "I".to_owned(),
-        }),
-    )?;
-    activity_tree.add_activity(
-        10,
-        9,
-        Activity::Unknown(ActivityUnknown {
-            state: ActivityState::Stopped,
-            text: "J".to_owned(),
-        }),
-    )?;
-
-    Ok(activity_tree)
-}
-
 #[test]
 fn forward_tree_order() -> Result<(), Box<dyn std::error::Error>> {
     let activity_tree = build_example_tree()?;
     let nodes = ForwardTreeIter::new(
         &activity_tree,
         None,
-        |entry| match *entry.get_activity_id().deref() {
+        is_match_predicate,
-            2 | 5 | 10 => true,
+        is_transparent_predicate,
-            _ => false,
+        is_alive_predicate,
-        },
-        |entry| match *entry.get_activity_id().deref() {
-            4 => true,
-            _ => false,
-        },
-        |entry| match *entry.get_activity_id().deref() {
-            1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 => true,
-            _ => false,
-        },
     );
 
     let output: Vec<_> = nodes
@@ -124,13 +29,20 @@ fn forward_tree_order() -> Result<(), Box<dyn std::error::Error>> {
         })
         .collect();
     let expected = vec![
-        (1, false, false, "Unknown(A)".into()),
+        (0, false, false, "Unknown(N1)".into()),
-        (2, true, false, "Unknown(B)".into()),
+        (1, true, false, "Unknown(N2)".into()),
-        (3, false, true, "Unknown(D)".into()),
+        (2, false, true, "Realize".into()), // N4
-        (3, true, false, "Unknown(E)".into()),
+        (2, true, false, "Unknown(N5)".into()),
-        (2, false, false, "Unknown(H)".into()),
+        (1, false, false, "Unknown(N8)".into()),
-        (3, false, false, "Unknown(I)".into()),
+        (2, false, false, "Unknown(N9)".into()),
-        (4, true, false, "Unknown(J)".into()),
+        (3, true, false, "Unknown(N10)".into()),
+        (0, false, false, "Unknown(N11)".into()),
+        (1, true, false, "Unknown(N12)".into()),
+        (2, false, true, "Realize".into()), // N14
+        (2, true, false, "Unknown(N15)".into()),
+        (1, false, false, "Unknown(N18)".into()),
+        (2, false, false, "Unknown(N19)".into()),
+        (3, true, false, "Unknown(N20)".into()),
     ];
 
     assert_eq!(output, expected);
@@ -144,18 +56,9 @@ fn start_from_a() -> Result<(), Box<dyn std::error::Error>> {
     let nodes = ForwardTreeIter::new(
         &activity_tree,
         Some(activity_tree.get(&activity_tree.get_activity_id(1)?)),
-        |entry| match *entry.get_activity_id().deref() {
+        is_match_predicate,
-            2 | 5 | 10 => true,
+        is_transparent_predicate,
-            _ => false,
+        is_alive_predicate,
-        },
-        |entry| match *entry.get_activity_id().deref() {
-            4 => true,
-            _ => false,
-        },
-        |entry| match *entry.get_activity_id().deref() {
-            1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 => true,
-            _ => false,
-        },
     );
 
     let output: Vec<_> = nodes
@@ -171,12 +74,12 @@ fn start_from_a() -> Result<(), Box<dyn std::error::Error>> {
         })
         .collect();
     let expected = vec![
-        (1, true, false, "Unknown(B)".into()),
+        (0, true, false, "Unknown(N2)".into()),
-        (2, false, true, "Unknown(D)".into()),
+        (1, false, true, "Realize".into()), // N4
-        (2, true, false, "Unknown(E)".into()),
+        (1, true, false, "Unknown(N5)".into()),
-        (1, false, false, "Unknown(H)".into()),
+        (0, false, false, "Unknown(N8)".into()),
-        (2, false, false, "Unknown(I)".into()),
+        (1, false, false, "Unknown(N9)".into()),
-        (3, true, false, "Unknown(J)".into()),
+        (2, true, false, "Unknown(N10)".into()),
     ];
 
     assert_eq!(output, expected);
@@ -190,18 +93,9 @@ fn start_from_h() -> Result<(), Box<dyn std::error::Error>> {
     let nodes = ForwardTreeIter::new(
         &activity_tree,
         Some(activity_tree.get(&activity_tree.get_activity_id(8)?)),
-        |entry| match *entry.get_activity_id().deref() {
+        is_match_predicate,
-            2 | 5 | 10 => true,
+        is_transparent_predicate,
-            _ => false,
+        is_alive_predicate,
-        },
-        |entry| match *entry.get_activity_id().deref() {
-            4 => true,
-            _ => false,
-        },
-        |entry| match *entry.get_activity_id().deref() {
-            1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 => true,
-            _ => false,
-        },
     );
 
     let output: Vec<_> = nodes
@@ -217,8 +111,8 @@ fn start_from_h() -> Result<(), Box<dyn std::error::Error>> {
         })
         .collect();
     let expected = vec![
-        (1, false, false, "Unknown(I)".into()),
+        (0, false, false, "Unknown(N9)".into()),
-        (2, true, false, "Unknown(J)".into()),
+        (1, true, false, "Unknown(N10)".into()),
     ];
 
     assert_eq!(output, expected);
@@ -232,18 +126,9 @@ fn start_from_c() -> Result<(), Box<dyn std::error::Error>> {
     let nodes = ForwardTreeIter::new(
         &activity_tree,
         Some(activity_tree.get(&activity_tree.get_activity_id(3)?)),
-        |entry| match *entry.get_activity_id().deref() {
+        is_match_predicate,
-            2 | 5 | 10 => true,
+        is_transparent_predicate,
-            _ => false,
+        is_alive_predicate,
-        },
-        |entry| match *entry.get_activity_id().deref() {
-            4 => true,
-            _ => false,
-        },
-        |entry| match *entry.get_activity_id().deref() {
-            1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 => true,
-            _ => false,
-        },
     );
 
     let output: Vec<_> = nodes

src/nix_util/tree_iter/mod.rs

@@ -1,6 +1,14 @@
+#[cfg(test)]
+mod test_util;
+#[cfg(test)]
+mod tests;
+
 mod forward_tree_iter;
+mod original_implementation;
 mod reverse_tree_iter;
 mod stack_entry;
 
 pub(crate) use forward_tree_iter::ForwardTreeIter;
+pub(crate) use original_implementation::DrawDagEntry;
+pub(crate) use original_implementation::get_draw_order;
 pub(crate) use reverse_tree_iter::ReverseTreeIter;

src/nix_util/tree_iter/original_implementation/benchmarks.rs

@@ -0,0 +1,85 @@
+use test::Bencher;
+use test::black_box;
+
+use crate::nix_util::activity::Activity;
+use crate::nix_util::activity::ActivityRealize;
+use crate::nix_util::activity::ActivityState;
+use crate::nix_util::activity::ActivityUnknown;
+use crate::nix_util::activity_tree::ActivityTree;
+
+use super::get_draw_order;
+
+fn build_example_tree(
+    num_levels: u64,
+    num_children_per_node: u64,
+) -> Result<ActivityTree, Box<dyn std::error::Error>> {
+    let mut activity_tree = ActivityTree::new();
+    let mut next_index = 1;
+    let mut previous_level: Vec<u64> = vec![0];
+
+    for _ in 0..num_levels {
+        let mut current_parents = Vec::new();
+        std::mem::swap(&mut previous_level, &mut current_parents);
+        for parent in current_parents {
+            for _ in 0..num_children_per_node {
+                // transparent = prime
+                let activity = if primal::is_prime(next_index as u64) {
+                    Activity::Realize(ActivityRealize {
+                        state: ActivityState::Started {
+                            progress_numerator: 0,
+                            progress_denominator: 0,
+                            progress_running: 0,
+                            progress_failed: 0,
+                        },
+                    })
+                } else {
+                    Activity::Unknown(ActivityUnknown {
+                        state: ActivityState::Started {
+                            progress_numerator: 0,
+                            progress_denominator: 0,
+                            progress_running: 0,
+                            progress_failed: 0,
+                        },
+                        text: format!("N{next_index}"),
+                    })
+                };
+                // if next_index is prime {} else {}
+                activity_tree.add_activity(next_index, parent, activity)?;
+                previous_level.push(next_index);
+                next_index += 1;
+            }
+        }
+    }
+
+    Ok(activity_tree)
+}
+
+/// Test a tree with few levels but many nodes per level.
+#[bench]
+fn bench_shallow_wide_tree(b: &mut Bencher) -> Result<(), Box<dyn std::error::Error>> {
+    let num_levels: u64 = 3;
+    let num_children_per_node: u64 = 27;
+
+    let activity_tree = build_example_tree(num_levels, num_children_per_node)?;
+
+    b.iter(|| {
+        let _ = black_box(get_draw_order(&activity_tree));
+    });
+
+    Ok(())
+}
+
+/// Test a tree with many levels but few nodes per level.
+#[bench]
+fn bench_deep_narrow_tree(b: &mut Bencher) -> Result<(), Box<dyn std::error::Error>> {
+    let num_levels: u64 = 9;
+    let num_children_per_node: u64 = 3;
+
+    let activity_tree = build_example_tree(num_levels, num_children_per_node)?;
+
+    b.iter(|| {
+        let _ = black_box(get_draw_order(&activity_tree));
+    });
+
+    Ok(())
+}

src/nix_util/tree_iter/original_implementation/mod.rs

@@ -0,0 +1,112 @@
+#[cfg(test)]
+mod benchmarks;
+#[cfg(test)]
+mod tests;
+mod transparent_iter;
+
+use crate::nix_util::activity_tree::ActivityId;
+use crate::nix_util::activity_tree::ActivityTree;
+use crate::nix_util::activity_tree::ActivityTreeEntry;
+
+use self::transparent_iter::TransparentIter;
+
+pub(crate) fn get_draw_order(activity_tree: &ActivityTree) -> Vec<DrawDagEntry> {
+    let mut draw_order: Vec<DrawDagEntry> = Vec::new();
+    let mut stack: Vec<DrawStackEntry> =
+        get_children_in_order(activity_tree, activity_tree.get_root_id())
+            .filter_map(|child| {
+                if child.get_activity().is_active() {
+                    Some(DrawStackEntry::HasNotVisitedChildren(DrawDagEntry {
+                        activity_id: child.get_activity_id().clone(),
+                        depth: Vec::new(),
+                        has_later_siblings: true,
+                    }))
+                } else {
+                    None
+                }
+            })
+            .collect();
+    if stack.len() == 0 {
+        return draw_order;
+    }
+    stack
+        .last_mut()
+        .expect("If-statement ensured this is Some()")
+        .set_no_later_siblings();
+
+    while !stack.is_empty() {
+        let current_entry = stack.pop().expect("While-loop ensured this is Some.");
+        match current_entry {
+            DrawStackEntry::HasNotVisitedChildren(draw_dag_entry) => {
+                let current_id = draw_dag_entry.activity_id.clone();
+                let mut current_depth = draw_dag_entry.depth.clone();
+                current_depth.push(draw_dag_entry.has_later_siblings);
+                stack.push(DrawStackEntry::VisitedChildren(draw_dag_entry));
+                let children: Vec<ActivityId> = get_children_in_order(activity_tree, current_id)
+                    .filter_map(|child| {
+                        if child.get_activity().is_active() {
+                            Some(child.get_activity_id().clone())
+                        } else {
+                            None
+                        }
+                    })
+                    .collect();
+                let has_children = !children.is_empty();
+                stack.extend(children.into_iter().map(|child_id| {
+                    DrawStackEntry::HasNotVisitedChildren(DrawDagEntry {
+                        activity_id: child_id,
+                        depth: current_depth.clone(),
+                        has_later_siblings: true,
+                    })
+                }));
+                if has_children {
+                    stack
+                        .last_mut()
+                        .expect("If-statement ensured this is Some()")
+                        .set_no_later_siblings();
+                }
+            }
+            DrawStackEntry::VisitedChildren(draw_dag_entry) => {
+                draw_order.push(draw_dag_entry);
+            }
+        };
+    }
+    draw_order
+}
+
+fn get_children_in_order(
+    activity_tree: &ActivityTree,
+    parent_id: ActivityId,
+) -> impl Iterator<Item = &ActivityTreeEntry> {
+    let parent = activity_tree.get(&parent_id);
+    parent
+        .get_child_ids()
+        .iter()
+        .map(|child_id| activity_tree.get(child_id))
+        .flat_map(|child| TransparentIter::new(activity_tree, child))
+}
+
+enum DrawStackEntry {
+    HasNotVisitedChildren(DrawDagEntry),
+    VisitedChildren(DrawDagEntry),
+}
+
+#[derive(Debug, PartialEq)]
+pub(crate) struct DrawDagEntry {
+    pub(crate) activity_id: ActivityId,
+    pub(crate) depth: Vec<bool>,
+    pub(crate) has_later_siblings: bool,
+}
+
+impl DrawStackEntry {
+    fn set_no_later_siblings(&mut self) -> () {
+        match self {
+            DrawStackEntry::HasNotVisitedChildren(draw_dag_entry) => {
+                draw_dag_entry.has_later_siblings = false
+            }
+            DrawStackEntry::VisitedChildren(draw_dag_entry) => {
+                draw_dag_entry.has_later_siblings = false
+            }
+        };
+    }
+}

src/nix_util/tree_iter/original_implementation/tests.rs

@@ -0,0 +1 @@
+

src/nix_util/tree_iter/original_implementation/transparent_iter.rs

@@ -1,5 +1,6 @@
-use super::activity_tree::ActivityTree;
+use crate::nix_util::activity_tree::ActivityTree;
-use super::activity_tree::ActivityTreeEntry;
+use crate::nix_util::activity_tree::ActivityTreeEntry;
+use crate::nix_util::running_build::is_transparent_predicate;
 
 /// An iterator that returns either the original activity if it is not transparent, or if it is transparent, the earliest non-transparent children.
 pub(crate) struct TransparentIter<'tree> {
@@ -19,7 +20,7 @@ impl<'tree> Iterator for TransparentIter<'tree> {
             }
         };
 
-        if !origin.get_activity().is_transparent() {
+        if !is_transparent_predicate(origin) {
             let origin = self
                 .origin
                 .take()
@@ -34,7 +35,7 @@ impl<'tree> Iterator for TransparentIter<'tree> {
         loop {
             let current_entry = self.get_current_entry();
             if let Some(child) = current_entry {
-                if child.get_activity().is_transparent() {
+                if !is_transparent_predicate(child) {
                     self.child_index.push(0);
                 } else {
                     let last_index = self.child_index.last_mut().expect("Stack cannot be empty.");

src/nix_util/tree_iter/reverse_tree_iter/benchmarks.rs

@@ -5,25 +5,27 @@ use crate::nix_util::activity::ActivityState;
 use crate::nix_util::activity::ActivityUnknown;
 
 use test::Bencher;
+use test::black_box;
 
 use super::*;
 
-/// Build an ActivityTree matching the description at the top of the file.
 fn build_example_tree(
     num_levels: u64,
     num_children_per_node: u64,
 ) -> Result<ActivityTree, Box<dyn std::error::Error>> {
     let mut activity_tree = ActivityTree::new();
     let mut next_index = 1;
-    let mut previous_level: Vec<u64> = Vec::new();
+    let mut previous_level: Vec<u64> = vec![0];
 
     for _ in 0..num_levels {
-        if previous_level.is_empty() {
+        // Subsequent levels, add num_children to each node of the previous level.
-            // first level, add num_children
+        let mut current_parents = Vec::new();
+        std::mem::swap(&mut previous_level, &mut current_parents);
+        for parent in current_parents {
             for _ in 0..num_children_per_node {
                 activity_tree.add_activity(
                     next_index,
-                    0,
+                    parent,
                     Activity::Unknown(ActivityUnknown {
                         state: ActivityState::Stopped,
                         text: format!("N{next_index}"),
@@ -32,24 +34,6 @@ fn build_example_tree(
                 previous_level.push(next_index);
                 next_index += 1;
             }
-        } else {
-            // Subsequent levels, add num_children to each node of the previous level.
-            let mut current_parents = Vec::new();
-            std::mem::swap(&mut previous_level, &mut current_parents);
-            for parent in current_parents {
-                for _ in 0..num_children_per_node {
-                    activity_tree.add_activity(
-                        next_index,
-                        parent,
-                        Activity::Unknown(ActivityUnknown {
-                            state: ActivityState::Stopped,
-                            text: format!("N{next_index}"),
-                        }),
-                    )?;
-                    previous_level.push(next_index);
-                    next_index += 1;
-                }
-            }
         }
     }
 
@@ -90,9 +74,36 @@ fn bench_shallow_wide_tree(b: &mut Bencher) -> Result<(), Box<dyn std::error::Er
     Ok(())
 }
 
+/// Test a tree with few levels but many nodes per level.
+#[bench]
+fn bench_shallow_wide_tree_draw(b: &mut Bencher) -> Result<(), Box<dyn std::error::Error>> {
+    let num_levels: u64 = 3;
+    let num_children_per_node: u64 = 27;
+    let total_nodes = num_children_per_node.pow(num_levels as u32);
+
+    let primes = get_primes(total_nodes);
+    // match = power of 2
+    // transparent = prime
+    let activity_tree = build_example_tree(num_levels, num_children_per_node)?;
+
+    b.iter(|| {
+        let nodes = ReverseTreeIter::new(
+            &activity_tree,
+            None,
+            |entry| (*entry.get_activity_id().deref()).count_ones() == 1,
+            |entry| primes.contains(entry.get_activity_id().deref()),
+            |_entry| true,
+        );
+
+        let _ = black_box(nodes.get_draw_order());
+    });
+
+    Ok(())
+}
+
 /// Test a tree with many levels but few nodes per level.
 #[bench]
-fn bench_deep_narrow_tree(b: &mut Bencher) -> Result<(), Box<dyn std::error::Error>> {
+fn bench_deep_narrow_tree_draw(b: &mut Bencher) -> Result<(), Box<dyn std::error::Error>> {
     let num_levels: u64 = 9;
     let num_children_per_node: u64 = 3;
     let total_nodes = num_children_per_node.pow(num_levels as u32);
@@ -111,7 +122,7 @@ fn bench_deep_narrow_tree(b: &mut Bencher) -> Result<(), Box<dyn std::error::Err
             |_entry| true,
         );
 
-        for _ in nodes {}
+        let _ = black_box(nodes.get_draw_order());
     });
 
     Ok(())

src/nix_util/tree_iter/reverse_tree_iter/mod.rs

@@ -8,6 +8,7 @@ use std::ops::Deref;
 use crate::nix_util::activity_tree::ActivityTree;
 use crate::nix_util::activity_tree::ActivityTreeEntry;
 
+use super::original_implementation::DrawDagEntry;
 use super::stack_entry::StackEntry;
 
 /// An iterator over the activity tree that will return nodes in the tree matching the supplied criteria.
@@ -43,13 +44,13 @@ use super::stack_entry::StackEntry;
 /// you would get the following output:
 ///
 /// ```text
-/// 4   True    False   J
+/// 3   True    False   J
-/// 3   False   False   I
+/// 2   False   False   I
-/// 2   False   False   H
+/// 1   False   False   H
-/// 3   True    False   E
+/// 2   True    False   E
-/// 3   False   True    D
+/// 2   False   True    D
-/// 2   True    False   B
+/// 1   True    False   B
-/// 1   False   False   A
+/// 0   False   False   A
 /// ```
 pub(crate) struct ReverseTreeIter<'tree, MP, TP, AP> {
     activity_tree: &'tree ActivityTree,
@@ -115,6 +116,36 @@ where
             .skip(1)
             .filter(|node| node.is_visited())
     }
+
+    pub(crate) fn get_draw_order(self) -> Vec<DrawDagEntry> {
+        let mut order = Vec::new();
+        let mut walk_depth: Vec<usize> = Vec::new();
+
+        for (inp_depth, _is_match, _is_transparent, entry) in
+            self.filter(|(_inp_depth, _is_match, is_transparent, _entry)| !*is_transparent)
+        {
+            let mut depth = vec![false; inp_depth];
+            let mut high_water_mark = inp_depth;
+            for preceding_depth in walk_depth.iter().rev() {
+                if *preceding_depth < high_water_mark {
+                    depth[*preceding_depth] = true;
+                    high_water_mark = *preceding_depth;
+                }
+            }
+            order.push(DrawDagEntry {
+                activity_id: entry.get_activity_id().clone(),
+                depth,
+                has_later_siblings: walk_depth
+                    .iter()
+                    .rev()
+                    .take_while(|wd| **wd >= inp_depth)
+                    .any(|wd| *wd == inp_depth),
+            });
+            walk_depth.push(inp_depth);
+        }
+
+        order
+    }
 }
 
 impl<'tree, MP, TP, AP> Iterator for ReverseTreeIter<'tree, MP, TP, AP>
@@ -126,6 +157,8 @@ where
     type Item = (usize, bool, bool, &'tree ActivityTreeEntry);
 
     fn next(&mut self) -> Option<Self::Item> {
+        let origin_activity_id = *self.origin.get_activity_id().deref();
+
         // Walk through stack
         loop {
             let mut should_check_for_output = false;
@@ -144,8 +177,8 @@ where
                 let is_transparent = stack_entry.is_transparent();
 
                 // If we've already processed the children, remove it from the stack.
-                if stack_entry.is_visited() {
+                if is_visited {
-                    if stack_entry.should_announce() {
+                    if should_announce && *node.get_activity_id().deref() != origin_activity_id {
                         let output = Some(self.announce(node, is_match, is_transparent));
                         self.stack.pop();
                         return output;
@@ -158,7 +191,7 @@ where
             };
 
             if is_visited {
-                if should_announce {
+                if should_announce && *node.get_activity_id().deref() != origin_activity_id {
                     let output = Some(self.announce(node, is_match, is_transparent));
                     self.stack.pop();
                     return output;

src/nix_util/tree_iter/reverse_tree_iter/tests.rs

@@ -1,114 +1,19 @@
-use crate::nix_util::activity::Activity;
+use crate::nix_util::running_build::is_transparent_predicate;
-use crate::nix_util::activity::ActivityState;
+use crate::nix_util::tree_iter::test_util::build_example_tree;
-use crate::nix_util::activity::ActivityUnknown;
+use crate::nix_util::tree_iter::test_util::is_alive_predicate;
+use crate::nix_util::tree_iter::test_util::is_match_predicate;
 
 use super::*;
 
-/// Build an ActivityTree matching the description at the top of the file.
-fn build_example_tree() -> Result<ActivityTree, Box<dyn std::error::Error>> {
-    let mut activity_tree = ActivityTree::new();
-    activity_tree.add_activity(
-        1,
-        0,
-        Activity::Unknown(ActivityUnknown {
-            state: ActivityState::Stopped,
-            text: "A".to_owned(),
-        }),
-    )?;
-    activity_tree.add_activity(
-        2,
-        1,
-        Activity::Unknown(ActivityUnknown {
-            state: ActivityState::Stopped,
-            text: "B".to_owned(),
-        }),
-    )?;
-    activity_tree.add_activity(
-        3,
-        2,
-        Activity::Unknown(ActivityUnknown {
-            state: ActivityState::Stopped,
-            text: "C".to_owned(),
-        }),
-    )?;
-    activity_tree.add_activity(
-        4,
-        2,
-        Activity::Unknown(ActivityUnknown {
-            state: ActivityState::Stopped,
-            text: "D".to_owned(),
-        }),
-    )?;
-    activity_tree.add_activity(
-        5,
-        4,
-        Activity::Unknown(ActivityUnknown {
-            state: ActivityState::Stopped,
-            text: "E".to_owned(),
-        }),
-    )?;
-    activity_tree.add_activity(
-        6,
-        4,
-        Activity::Unknown(ActivityUnknown {
-            state: ActivityState::Stopped,
-            text: "F".to_owned(),
-        }),
-    )?;
-    activity_tree.add_activity(
-        7,
-        1,
-        Activity::Unknown(ActivityUnknown {
-            state: ActivityState::Stopped,
-            text: "G".to_owned(),
-        }),
-    )?;
-    activity_tree.add_activity(
-        8,
-        1,
-        Activity::Unknown(ActivityUnknown {
-            state: ActivityState::Stopped,
-            text: "H".to_owned(),
-        }),
-    )?;
-    activity_tree.add_activity(
-        9,
-        8,
-        Activity::Unknown(ActivityUnknown {
-            state: ActivityState::Stopped,
-            text: "I".to_owned(),
-        }),
-    )?;
-    activity_tree.add_activity(
-        10,
-        9,
-        Activity::Unknown(ActivityUnknown {
-            state: ActivityState::Stopped,
-            text: "J".to_owned(),
-        }),
-    )?;
-
-    Ok(activity_tree)
-}
-
 #[test]
 fn reverse_tree_order() -> Result<(), Box<dyn std::error::Error>> {
     let activity_tree = build_example_tree()?;
     let nodes = ReverseTreeIter::new(
         &activity_tree,
         None,
-        |entry| match *entry.get_activity_id().deref() {
+        is_match_predicate,
-            2 | 5 | 10 => true,
+        is_transparent_predicate,
-            _ => false,
+        is_alive_predicate,
-        },
-        |entry| match *entry.get_activity_id().deref() {
-            4 => true,
-            _ => false,
-        },
-        |entry| match *entry.get_activity_id().deref() {
-            1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 => true,
-            _ => false,
-        },
     );
 
     let output: Vec<_> = nodes
@@ -124,13 +29,20 @@ fn reverse_tree_order() -> Result<(), Box<dyn std::error::Error>> {
         })
         .collect();
     let expected = vec![
-        (4, true, false, "Unknown(J)".into()),
+        (3, true, false, "Unknown(N20)".into()),
-        (3, false, false, "Unknown(I)".into()),
+        (2, false, false, "Unknown(N19)".into()),
-        (2, false, false, "Unknown(H)".into()),
+        (1, false, false, "Unknown(N18)".into()),
-        (3, true, false, "Unknown(E)".into()),
+        (2, true, false, "Unknown(N15)".into()),
-        (3, false, true, "Unknown(D)".into()),
+        (2, false, true, "Realize".into()),
-        (2, true, false, "Unknown(B)".into()),
+        (1, true, false, "Unknown(N12)".into()),
-        (1, false, false, "Unknown(A)".into()),
+        (0, false, false, "Unknown(N11)".into()),
+        (3, true, false, "Unknown(N10)".into()),
+        (2, false, false, "Unknown(N9)".into()),
+        (1, false, false, "Unknown(N8)".into()),
+        (2, true, false, "Unknown(N5)".into()),
+        (2, false, true, "Realize".into()),
+        (1, true, false, "Unknown(N2)".into()),
+        (0, false, false, "Unknown(N1)".into()),
     ];
 
     assert_eq!(output, expected);
@@ -139,23 +51,14 @@ fn reverse_tree_order() -> Result<(), Box<dyn std::error::Error>> {
 }
 
 #[test]
-fn start_from_a() -> Result<(), Box<dyn std::error::Error>> {
+fn start_from_1() -> Result<(), Box<dyn std::error::Error>> {
     let activity_tree = build_example_tree()?;
     let nodes = ReverseTreeIter::new(
         &activity_tree,
         Some(activity_tree.get(&activity_tree.get_activity_id(1)?)),
-        |entry| match *entry.get_activity_id().deref() {
+        is_match_predicate,
-            2 | 5 | 10 => true,
+        is_transparent_predicate,
-            _ => false,
+        is_alive_predicate,
-        },
-        |entry| match *entry.get_activity_id().deref() {
-            4 => true,
-            _ => false,
-        },
-        |entry| match *entry.get_activity_id().deref() {
-            1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 => true,
-            _ => false,
-        },
     );
 
     let output: Vec<_> = nodes
@@ -171,12 +74,12 @@ fn start_from_a() -> Result<(), Box<dyn std::error::Error>> {
         })
         .collect();
     let expected = vec![
-        (3, true, false, "Unknown(J)".into()),
+        (3, true, false, "Unknown(N10)".into()),
-        (2, false, false, "Unknown(I)".into()),
+        (2, false, false, "Unknown(N9)".into()),
-        (1, false, false, "Unknown(H)".into()),
+        (1, false, false, "Unknown(N8)".into()),
-        (2, true, false, "Unknown(E)".into()),
+        (2, true, false, "Unknown(N5)".into()),
-        (2, false, true, "Unknown(D)".into()),
+        (2, false, true, "Realize".into()), // N4
-        (1, true, false, "Unknown(B)".into()),
+        (1, true, false, "Unknown(N2)".into()),
     ];
 
     assert_eq!(output, expected);
@@ -185,23 +88,14 @@ fn start_from_a() -> Result<(), Box<dyn std::error::Error>> {
 }
 
 #[test]
-fn start_from_h() -> Result<(), Box<dyn std::error::Error>> {
+fn start_from_8() -> Result<(), Box<dyn std::error::Error>> {
     let activity_tree = build_example_tree()?;
     let nodes = ReverseTreeIter::new(
         &activity_tree,
         Some(activity_tree.get(&activity_tree.get_activity_id(8)?)),
-        |entry| match *entry.get_activity_id().deref() {
+        is_match_predicate,
-            2 | 5 | 10 => true,
+        is_transparent_predicate,
-            _ => false,
+        is_alive_predicate,
-        },
-        |entry| match *entry.get_activity_id().deref() {
-            4 => true,
-            _ => false,
-        },
-        |entry| match *entry.get_activity_id().deref() {
-            1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 => true,
-            _ => false,
-        },
     );
 
     let output: Vec<_> = nodes
@@ -217,8 +111,8 @@ fn start_from_h() -> Result<(), Box<dyn std::error::Error>> {
         })
         .collect();
     let expected = vec![
-        (2, true, false, "Unknown(J)".into()),
+        (2, true, false, "Unknown(N10)".into()),
-        (1, false, false, "Unknown(I)".into()),
+        (1, false, false, "Unknown(N9)".into()),
     ];
 
     assert_eq!(output, expected);
@@ -227,23 +121,14 @@ fn start_from_h() -> Result<(), Box<dyn std::error::Error>> {
 }
 
 #[test]
-fn start_from_c() -> Result<(), Box<dyn std::error::Error>> {
+fn start_from_3() -> Result<(), Box<dyn std::error::Error>> {
     let activity_tree = build_example_tree()?;
     let nodes = ReverseTreeIter::new(
         &activity_tree,
         Some(activity_tree.get(&activity_tree.get_activity_id(3)?)),
-        |entry| match *entry.get_activity_id().deref() {
+        is_match_predicate,
-            2 | 5 | 10 => true,
+        is_transparent_predicate,
-            _ => false,
+        is_alive_predicate,
-        },
-        |entry| match *entry.get_activity_id().deref() {
-            4 => true,
-            _ => false,
-        },
-        |entry| match *entry.get_activity_id().deref() {
-            1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 => true,
-            _ => false,
-        },
     );
 
     let output: Vec<_> = nodes
@@ -264,3 +149,82 @@ fn start_from_c() -> Result<(), Box<dyn std::error::Error>> {
 
     Ok(())
 }
+
+#[test]
+fn reverse_tree_draw_order() -> Result<(), Box<dyn std::error::Error>> {
+    let activity_tree = build_example_tree()?;
+    let expected = vec![
+        DrawDagEntry {
+            activity_id: activity_tree.get_activity_id(20).unwrap(),
+            depth: vec![false, false, false],
+            has_later_siblings: false,
+        },
+        DrawDagEntry {
+            activity_id: activity_tree.get_activity_id(19).unwrap(),
+            depth: vec![false, false],
+            has_later_siblings: false,
+        },
+        DrawDagEntry {
+            activity_id: activity_tree.get_activity_id(18).unwrap(),
+            depth: vec![false],
+            has_later_siblings: false,
+        },
+        DrawDagEntry {
+            activity_id: activity_tree.get_activity_id(15).unwrap(),
+            depth: vec![false, true],
+            has_later_siblings: false,
+        },
+        DrawDagEntry {
+            activity_id: activity_tree.get_activity_id(12).unwrap(),
+            depth: vec![false],
+            has_later_siblings: true,
+        },
+        DrawDagEntry {
+            activity_id: activity_tree.get_activity_id(11).unwrap(),
+            depth: vec![],
+            has_later_siblings: false,
+        },
+        DrawDagEntry {
+            activity_id: activity_tree.get_activity_id(10).unwrap(),
+            depth: vec![true, false, false],
+            has_later_siblings: false,
+        },
+        DrawDagEntry {
+            activity_id: activity_tree.get_activity_id(9).unwrap(),
+            depth: vec![true, false],
+            has_later_siblings: false,
+        },
+        DrawDagEntry {
+            activity_id: activity_tree.get_activity_id(8).unwrap(),
+            depth: vec![true],
+            has_later_siblings: false,
+        },
+        DrawDagEntry {
+            activity_id: activity_tree.get_activity_id(5).unwrap(),
+            depth: vec![true, true],
+            has_later_siblings: false,
+        },
+        DrawDagEntry {
+            activity_id: activity_tree.get_activity_id(2).unwrap(),
+            depth: vec![true],
+            has_later_siblings: true,
+        },
+        DrawDagEntry {
+            activity_id: activity_tree.get_activity_id(1).unwrap(),
+            depth: vec![],
+            has_later_siblings: true,
+        },
+    ];
+
+    let reverse_draw_order = ReverseTreeIter::new(
+        &activity_tree,
+        None,
+        is_match_predicate,
+        is_transparent_predicate,
+        is_alive_predicate,
+    )
+    .get_draw_order();
+
+    assert_eq!(reverse_draw_order, expected);
+    Ok(())
+}

src/nix_util/tree_iter/test_util.rs

@@ -0,0 +1,392 @@
+use std::ops::Deref;
+
+use crate::nix_util::activity::Activity;
+use crate::nix_util::activity::ActivityRealize;
+use crate::nix_util::activity::ActivityState;
+use crate::nix_util::activity::ActivityUnknown;
+use crate::nix_util::activity_tree::ActivityTree;
+use crate::nix_util::activity_tree::ActivityTreeEntry;
+
+impl Activity {
+    pub(crate) fn start(&mut self) -> () {
+        match self {
+            Activity::Root(_activity_root) => {
+                panic!("Attempted to start root activity.");
+            }
+            Activity::Unknown(activity_unknown) => {
+                activity_unknown.state = ActivityState::Started {
+                    progress_numerator: 0,
+                    progress_denominator: 0,
+                    progress_running: 0,
+                    progress_failed: 0,
+                };
+            }
+            Activity::CopyPath(activity_copy_path) => {
+                activity_copy_path.state = ActivityState::Started {
+                    progress_numerator: 0,
+                    progress_denominator: 0,
+                    progress_running: 0,
+                    progress_failed: 0,
+                };
+            }
+            Activity::FileTransfer(activity_file_transfer) => {
+                activity_file_transfer.state = ActivityState::Started {
+                    progress_numerator: 0,
+                    progress_denominator: 0,
+                    progress_running: 0,
+                    progress_failed: 0,
+                };
+            }
+            Activity::Realize(activity_realize) => {
+                activity_realize.state = ActivityState::Started {
+                    progress_numerator: 0,
+                    progress_denominator: 0,
+                    progress_running: 0,
+                    progress_failed: 0,
+                };
+            }
+            Activity::CopyPaths(activity_copy_paths) => {
+                activity_copy_paths.state = ActivityState::Started {
+                    progress_numerator: 0,
+                    progress_denominator: 0,
+                    progress_running: 0,
+                    progress_failed: 0,
+                };
+            }
+            Activity::Builds(activity_builds) => {
+                activity_builds.state = ActivityState::Started {
+                    progress_numerator: 0,
+                    progress_denominator: 0,
+                    progress_running: 0,
+                    progress_failed: 0,
+                };
+            }
+            Activity::Build(activity_build) => {
+                activity_build.state = ActivityState::Started {
+                    progress_numerator: 0,
+                    progress_denominator: 0,
+                    progress_running: 0,
+                    progress_failed: 0,
+                };
+            }
+            Activity::OptimizeStore(activity_optimize_store) => {
+                activity_optimize_store.state = ActivityState::Started {
+                    progress_numerator: 0,
+                    progress_denominator: 0,
+                    progress_running: 0,
+                    progress_failed: 0,
+                };
+            }
+            Activity::VerifyPaths(activity_verify_paths) => {
+                activity_verify_paths.state = ActivityState::Started {
+                    progress_numerator: 0,
+                    progress_denominator: 0,
+                    progress_running: 0,
+                    progress_failed: 0,
+                };
+            }
+            Activity::Substitute(activity_substitute) => {
+                activity_substitute.state = ActivityState::Started {
+                    progress_numerator: 0,
+                    progress_denominator: 0,
+                    progress_running: 0,
+                    progress_failed: 0,
+                };
+            }
+            Activity::QueryPathInfo(activity_query_path_info) => {
+                activity_query_path_info.state = ActivityState::Started {
+                    progress_numerator: 0,
+                    progress_denominator: 0,
+                    progress_running: 0,
+                    progress_failed: 0,
+                };
+            }
+            Activity::PostBuildHook(activity_post_build_hook) => {
+                activity_post_build_hook.state = ActivityState::Started {
+                    progress_numerator: 0,
+                    progress_denominator: 0,
+                    progress_running: 0,
+                    progress_failed: 0,
+                };
+            }
+            Activity::BuildWaiting(activity_build_waiting) => {
+                activity_build_waiting.state = ActivityState::Started {
+                    progress_numerator: 0,
+                    progress_denominator: 0,
+                    progress_running: 0,
+                    progress_failed: 0,
+                };
+            }
+            Activity::FetchTree(activity_fetch_tree) => {
+                activity_fetch_tree.state = ActivityState::Started {
+                    progress_numerator: 0,
+                    progress_denominator: 0,
+                    progress_running: 0,
+                    progress_failed: 0,
+                };
+            }
+        }
+    }
+}
+
+/// Build the following ActivityTree:
+///
+///          𜸛𜸟 Unknown(N20)
+///       𜸛𜸟 Unknown(N19)
+///    𜸛𜸟 Unknown(N18)
+///    𜹈  𜸛𜸟 Unknown(N15)
+///    𜸨𜸟 Unknown(N12)
+/// 𜸛𜸟 Unknown(N11)
+/// 𜹈        𜸛𜸟 Unknown(N10)
+/// 𜹈     𜸛𜸟 Unknown(N9)
+/// 𜹈  𜸛𜸟 Unknown(N8)
+/// 𜹈  𜹈  𜸛𜸟 Unknown(N5)
+/// 𜹈  𜸨𜸟 Unknown(N2)
+/// 𜸨𜸟 Unknown(N1)
+pub(crate) fn build_example_tree() -> Result<ActivityTree, Box<dyn std::error::Error>> {
+    let instructions = vec![
+        BuildInstruction {
+            activity_id: 1,
+            parent_id: 0,
+            is_match: false,
+            is_transparent: false,
+        },
+        BuildInstruction {
+            activity_id: 2,
+            parent_id: 1,
+            is_match: true,
+            is_transparent: false,
+        },
+        BuildInstruction {
+            activity_id: 3,
+            parent_id: 2,
+            is_match: false,
+            is_transparent: false,
+        },
+        BuildInstruction {
+            activity_id: 4,
+            parent_id: 2,
+            is_match: false,
+            is_transparent: true,
+        },
+        BuildInstruction {
+            activity_id: 5,
+            parent_id: 4,
+            is_match: true,
+            is_transparent: false,
+        },
+        BuildInstruction {
+            activity_id: 6,
+            parent_id: 4,
+            is_match: false,
+            is_transparent: false,
+        },
+        BuildInstruction {
+            activity_id: 7,
+            parent_id: 1,
+            is_match: false,
+            is_transparent: false,
+        },
+        BuildInstruction {
+            activity_id: 8,
+            parent_id: 1,
+            is_match: false,
+            is_transparent: false,
+        },
+        BuildInstruction {
+            activity_id: 9,
+            parent_id: 8,
+            is_match: false,
+            is_transparent: false,
+        },
+        BuildInstruction {
+            activity_id: 10,
+            parent_id: 9,
+            is_match: true,
+            is_transparent: false,
+        },
+        BuildInstruction {
+            activity_id: 11,
+            parent_id: 0,
+            is_match: false,
+            is_transparent: false,
+        },
+        BuildInstruction {
+            activity_id: 12,
+            parent_id: 11,
+            is_match: true,
+            is_transparent: false,
+        },
+        BuildInstruction {
+            activity_id: 13,
+            parent_id: 12,
+            is_match: false,
+            is_transparent: false,
+        },
+        BuildInstruction {
+            activity_id: 14,
+            parent_id: 12,
+            is_match: false,
+            is_transparent: true,
+        },
+        BuildInstruction {
+            activity_id: 15,
+            parent_id: 14,
+            is_match: true,
+            is_transparent: false,
+        },
+        BuildInstruction {
+            activity_id: 16,
+            parent_id: 14,
+            is_match: false,
+            is_transparent: false,
+        },
+        BuildInstruction {
+            activity_id: 17,
+            parent_id: 11,
+            is_match: false,
+            is_transparent: false,
+        },
+        BuildInstruction {
+            activity_id: 18,
+            parent_id: 11,
+            is_match: false,
+            is_transparent: false,
+        },
+        BuildInstruction {
+            activity_id: 19,
+            parent_id: 18,
+            is_match: false,
+            is_transparent: false,
+        },
+        BuildInstruction {
+            activity_id: 20,
+            parent_id: 19,
+            is_match: true,
+            is_transparent: false,
+        },
+    ];
+
+    let activity_tree = build_activity_tree_from_instructions(&instructions, false)?;
+
+    Ok(activity_tree)
+}
+
+#[derive(Debug, Clone)]
+pub(crate) struct BuildInstruction {
+    activity_id: u64,
+    parent_id: u64,
+    is_transparent: bool,
+    is_match: bool,
+}
+
+pub(crate) fn get_every_possible_addition<'old, 'new>(
+    old_state: &'old Vec<BuildInstruction>,
+) -> Vec<Vec<BuildInstruction>> {
+    let mut out = Vec::new();
+    for is_transparent in [true, false] {
+        for is_match in [true, false] {
+            let next_activity_id = old_state.last().map(|bi| bi.activity_id).unwrap_or(0) + 1;
+            for parent_id in 0..next_activity_id {
+                let mut new_state = old_state.clone();
+                new_state.push(BuildInstruction {
+                    activity_id: next_activity_id,
+                    parent_id,
+                    is_transparent,
+                    is_match,
+                });
+                out.push(new_state);
+            }
+        }
+    }
+    out
+}
+
+pub(crate) fn build_activity_tree_from_instructions(
+    instructions: &Vec<BuildInstruction>,
+    start_parents: bool,
+) -> Result<ActivityTree, Box<dyn std::error::Error>> {
+    let mut activity_tree = ActivityTree::new();
+    for instruct in instructions {
+        match (instruct.is_transparent, instruct.is_match) {
+            (true, true) => {
+                activity_tree.add_activity(
+                    instruct.activity_id,
+                    instruct.parent_id,
+                    Activity::Realize(ActivityRealize {
+                        state: ActivityState::Started {
+                            progress_numerator: 0,
+                            progress_denominator: 0,
+                            progress_running: 0,
+                            progress_failed: 0,
+                        },
+                    }),
+                )?;
+                // Walk up tree marking parents as match
+                if start_parents {
+                    let mut parent_id = instruct.parent_id;
+                    while parent_id > 0 {
+                        let parent =
+                            activity_tree.get_mut(&activity_tree.get_activity_id(parent_id)?);
+                        parent.get_mut_activity().start();
+                        parent_id = *parent.get_parent_id().deref();
+                    }
+                }
+            }
+            (true, false) => {
+                activity_tree.add_activity(
+                    instruct.activity_id,
+                    instruct.parent_id,
+                    Activity::Realize(ActivityRealize {
+                        state: ActivityState::Stopped,
+                    }),
+                )?;
+            }
+            (false, true) => {
+                activity_tree.add_activity(
+                    instruct.activity_id,
+                    instruct.parent_id,
+                    Activity::Unknown(ActivityUnknown {
+                        state: ActivityState::Started {
+                            progress_numerator: 0,
+                            progress_denominator: 0,
+                            progress_running: 0,
+                            progress_failed: 0,
+                        },
+                        text: format!("N{}", instruct.activity_id),
+                    }),
+                )?;
+                // Walk up tree marking parents as match
+                if start_parents {
+                    let mut parent_id = instruct.parent_id;
+                    while parent_id > 0 {
+                        let parent =
+                            activity_tree.get_mut(&activity_tree.get_activity_id(parent_id)?);
+                        parent.get_mut_activity().start();
+                        parent_id = *parent.get_parent_id().deref();
+                    }
+                }
+            }
+            (false, false) => {
+                activity_tree.add_activity(
+                    instruct.activity_id,
+                    instruct.parent_id,
+                    Activity::Unknown(ActivityUnknown {
+                        state: ActivityState::Stopped,
+                        text: format!("N{}", instruct.activity_id),
+                    }),
+                )?;
+            }
+        }
+    }
+
+    Ok(activity_tree)
+}
+
+pub(crate) fn is_match_predicate(entry: &ActivityTreeEntry) -> bool {
+    entry.get_activity().is_active()
+}
+
+pub(crate) fn is_alive_predicate(_entry: &ActivityTreeEntry) -> bool {
+    true
+}

src/nix_util/tree_iter/tests.rs

@@ -0,0 +1,55 @@
+use crate::nix_util::running_build::is_transparent_predicate;
+use crate::nix_util::running_build::print_dag;
+
+use super::ReverseTreeIter;
+use super::get_draw_order;
+use super::test_util::BuildInstruction;
+use super::test_util::build_activity_tree_from_instructions;
+use super::test_util::get_every_possible_addition;
+
+fn compare_single_tree(
+    instructions: &Vec<BuildInstruction>,
+) -> Result<(), Box<dyn std::error::Error>> {
+    let activity_tree = build_activity_tree_from_instructions(instructions, true)?;
+    let original_draw_order = get_draw_order(&activity_tree);
+    let reverse_draw_order = ReverseTreeIter::new(
+        &activity_tree,
+        None,
+        |entry| entry.get_activity().is_active(),
+        is_transparent_predicate,
+        |_entry| true,
+    )
+    .get_draw_order();
+
+    if original_draw_order != reverse_draw_order {
+        println!("Draw order mismatch!");
+        println!("Instructions: {:?}", instructions);
+        println!("Original: {:?}", original_draw_order);
+        println!("Reverse: {:?}", reverse_draw_order);
+        print_dag(&activity_tree, original_draw_order);
+        print_dag(&activity_tree, reverse_draw_order);
+        return Err("mismatch".into());
+    }
+
+    Ok(())
+}
+
+#[test]
+#[ignore]
+fn reverse_tree_order_draw_order_iterative() -> Result<(), Box<dyn std::error::Error>> {
+    let mut prev_generation: Vec<Vec<BuildInstruction>> = Vec::new();
+    let mut current_generation: Vec<Vec<BuildInstruction>> = vec![vec![]];
+
+    // Iterate through every possible tree with N nodes.
+    for _ in 0..7 {
+        std::mem::swap(&mut prev_generation, &mut current_generation);
+        for old_state in prev_generation.drain(..) {
+            for new_state in get_every_possible_addition(&old_state) {
+                compare_single_tree(&new_state)?;
+                current_generation.push(new_state);
+            }
+        }
+    }
+
+    Ok(())
+}