Add a utility function to check the first element in an sexp.

src/compare/diff.rs

@@ -1,4 +1,5 @@
 use super::sexp::Token;
+use super::util::assert_name;
 use crate::compare::util::get_offsets;
 use crate::parser::Comment;
 use crate::parser::Document;
@@ -18,6 +19,7 @@ use crate::DynamicBlock;
 pub struct DiffResult {
     status: DiffStatus,
     name: String,
+    message: Option<String>,
     children: Vec<DiffResult>,
 }
 
@@ -71,11 +73,7 @@ pub fn compare_document<'s>(
     rust: &'s Document<'s>,
 ) -> Result<DiffResult, Box<dyn std::error::Error>> {
     let children = emacs.as_list()?;
-    let first_child = children.first().ok_or("Should have at least one child.")?;
+    assert_name(emacs, "org-data")?;
-    let first_child_text = first_child.as_atom()?;
-    if first_child_text != "org-data" {
-        return Err("Document should correspond to an org-data cell.".into());
-    }
     let mut child_status = Vec::new();
     let mut this_status = DiffStatus::Good;
 
@@ -112,6 +110,7 @@ pub fn compare_document<'s>(
     Ok(DiffResult {
         status: this_status,
         name: "document".to_owned(),
+        message: None,
         children: child_status,
     })
 }
@@ -122,11 +121,7 @@ fn compare_section<'s>(
     rust: &'s Section<'s>,
 ) -> Result<DiffResult, Box<dyn std::error::Error>> {
     let children = emacs.as_list()?;
-    let first_child = children.first().ok_or("Should have at least one child.")?;
+    assert_name(emacs, "section")?;
-    let first_child_text = first_child.as_atom()?;
-    if first_child_text != "section" {
-        return Err("Section should correspond to a section cell.".into());
-    }
     let mut child_status = Vec::new();
     let mut this_status = DiffStatus::Good;
 
@@ -155,6 +150,7 @@ fn compare_section<'s>(
     Ok(DiffResult {
         status: this_status,
         name: "section".to_owned(),
+        message: None,
         children: child_status,
     })
 }
@@ -165,11 +161,7 @@ fn compare_heading<'s>(
     rust: &'s Heading<'s>,
 ) -> Result<DiffResult, Box<dyn std::error::Error>> {
     let children = emacs.as_list()?;
-    let first_child = children.first().ok_or("Should have at least one child.")?;
+    assert_name(emacs, "headline")?;
-    let first_child_text = first_child.as_atom()?;
-    if first_child_text != "headline" {
-        return Err("Heading should correspond to a headline cell.".into());
-    }
     let mut child_status = Vec::new();
     let mut this_status = DiffStatus::Good;
 
@@ -205,6 +197,7 @@ fn compare_heading<'s>(
     Ok(DiffResult {
         status: this_status,
         name: "heading".to_owned(),
+        message: None,
         children: child_status,
     })
 }
@@ -231,13 +224,7 @@ fn compare_paragraph<'s>(
     rust: &'s Paragraph<'s>,
 ) -> Result<DiffResult, Box<dyn std::error::Error>> {
     let children = emacs.as_list()?;
-    let first_child = children
+    assert_name(emacs, "paragraph")?;
-        .first()
-        .ok_or("Should have at least one child.")?
-        .as_atom()?;
-    if first_child != "paragraph" {
-        return Err("Paragraph should correspond to a paragraph cell.".into());
-    }
     let mut child_status = Vec::new();
     let mut this_status = DiffStatus::Good;
 
@@ -264,6 +251,7 @@ fn compare_paragraph<'s>(
     Ok(DiffResult {
         status: this_status,
         name: "paragraph".to_owned(),
+        message: None,
         children: child_status,
     })
 }
@@ -274,13 +262,7 @@ fn compare_plain_list<'s>(
     rust: &'s PlainList<'s>,
 ) -> Result<DiffResult, Box<dyn std::error::Error>> {
     let children = emacs.as_list()?;
-    let first_child = children
+    assert_name(emacs, "plain-list")?;
-        .first()
-        .ok_or("Should have at least one child.")?
-        .as_atom()?;
-    if first_child != "plain-list" {
-        return Err("Paragraph should correspond to a paragraph cell.".into());
-    }
     let mut child_status = Vec::new();
     let mut this_status = DiffStatus::Good;
 
@@ -309,6 +291,7 @@ fn compare_plain_list<'s>(
     Ok(DiffResult {
         status: this_status,
         name: "plain-list".to_owned(),
+        message: None,
         children: child_status,
     })
 }
@@ -319,13 +302,7 @@ fn compare_plain_list_item<'s>(
     rust: &'s PlainListItem<'s>,
 ) -> Result<DiffResult, Box<dyn std::error::Error>> {
     let children = emacs.as_list()?;
-    let first_child = children
+    assert_name(emacs, "item")?;
-        .first()
-        .ok_or("Should have at least one child.")?
-        .as_atom()?;
-    if first_child != "item" {
-        return Err("PlainListItem should correspond to an item cell.".into());
-    }
     let mut child_status = Vec::new();
     let mut this_status = DiffStatus::Good;
 
@@ -354,6 +331,7 @@ fn compare_plain_list_item<'s>(
     Ok(DiffResult {
         status: this_status,
         name: "plain-list-item".to_owned(),
+        message: None,
         children: child_status,
     })
 }
@@ -364,25 +342,14 @@ fn compare_greater_block<'s>(
     rust: &'s GreaterBlock<'s>,
 ) -> Result<DiffResult, Box<dyn std::error::Error>> {
     let children = emacs.as_list()?;
-    let first_child = children
+    assert_name(
-        .first()
+        emacs,
-        .ok_or("Should have at least one child.")?
+        match rust.name.to_lowercase().as_str() {
-        .as_atom()?;
+            "center" => "center-block",
-    match rust.name.to_lowercase().as_str() {
+            "quote" => "quote-block",
-        "center" => {
+            _ => todo!(),
-            if first_child != "center-block" {
+        },
-                return Err(
+    )?;
-                    "Center greater blocks should correspond to a center-block cell.".into(),
-                );
-            }
-        }
-        "quote" => {
-            if first_child != "quote-block" {
-                return Err("Quote greater blocks should correspond to a quote-block cell.".into());
-            }
-        }
-        _ => todo!(),
-    }
     let mut child_status = Vec::new();
     let mut this_status = DiffStatus::Good;
 
@@ -411,6 +378,7 @@ fn compare_greater_block<'s>(
     Ok(DiffResult {
         status: this_status,
         name: "greater-block".to_owned(),
+        message: None,
         children: child_status,
     })
 }
@@ -421,13 +389,7 @@ fn compare_dynamic_block<'s>(
     rust: &'s DynamicBlock<'s>,
 ) -> Result<DiffResult, Box<dyn std::error::Error>> {
     let children = emacs.as_list()?;
-    let first_child = children
+    assert_name(emacs, "dynamic-block")?;
-        .first()
-        .ok_or("Should have at least one child.")?
-        .as_atom()?;
-    if first_child != "dynamic-block" {
-        return Err("Dynamic block should correspond to a dynamic-block cell.".into());
-    }
     let mut child_status = Vec::new();
     let mut this_status = DiffStatus::Good;
 
@@ -456,6 +418,7 @@ fn compare_dynamic_block<'s>(
     Ok(DiffResult {
         status: this_status,
         name: "dynamic-block".to_owned(),
+        message: None,
         children: child_status,
     })
 }
@@ -466,13 +429,7 @@ fn compare_footnote_definition<'s>(
     rust: &'s FootnoteDefinition<'s>,
 ) -> Result<DiffResult, Box<dyn std::error::Error>> {
     let children = emacs.as_list()?;
-    let first_child = children
+    assert_name(emacs, "footnote-definition")?;
-        .first()
-        .ok_or("Should have at least one child.")?
-        .as_atom()?;
-    if first_child != "footnote-definition" {
-        return Err("Paragraph should correspond to a paragraph cell.".into());
-    }
     let mut child_status = Vec::new();
     let mut this_status = DiffStatus::Good;
 
@@ -501,6 +458,7 @@ fn compare_footnote_definition<'s>(
     Ok(DiffResult {
         status: this_status,
         name: "footnote-definition".to_owned(),
+        message: None,
         children: child_status,
     })
 }
@@ -511,13 +469,7 @@ fn compare_comment<'s>(
     rust: &'s Comment<'s>,
 ) -> Result<DiffResult, Box<dyn std::error::Error>> {
     let children = emacs.as_list()?;
-    let first_child = children
+    assert_name(emacs, "comment")?;
-        .first()
-        .ok_or("Should have at least one child.")?
-        .as_atom()?;
-    if first_child != "comment" {
-        return Err("Comment should correspond to a comment cell.".into());
-    }
     let mut child_status = Vec::new();
     let mut this_status = DiffStatus::Good;
 
@@ -542,6 +494,7 @@ fn compare_comment<'s>(
     Ok(DiffResult {
         status: this_status,
         name: "comment".to_owned(),
+        message: None,
         children: child_status,
     })
 }
@@ -552,13 +505,7 @@ fn compare_drawer<'s>(
     rust: &'s Drawer<'s>,
 ) -> Result<DiffResult, Box<dyn std::error::Error>> {
     let children = emacs.as_list()?;
-    let first_child = children
+    assert_name(emacs, "drawer")?;
-        .first()
-        .ok_or("Should have at least one child.")?
-        .as_atom()?;
-    if first_child != "drawer" {
-        return Err("Drawer should correspond to a drawer cell.".into());
-    }
     let mut child_status = Vec::new();
     let mut this_status = DiffStatus::Good;
 
@@ -587,6 +534,7 @@ fn compare_drawer<'s>(
     Ok(DiffResult {
         status: this_status,
         name: "drawer".to_owned(),
+        message: None,
         children: child_status,
     })
 }

src/compare/util.rs

@@ -1,5 +1,7 @@
 use crate::parser::Source;
 
+use super::sexp::Token;
+
 /// Check if the child string slice is a slice of the parent string slice.
 fn is_slice_of(parent: &str, child: &str) -> bool {
     let parent_start = parent.as_ptr() as usize;
@@ -19,3 +21,19 @@ pub fn get_offsets<'s, S: Source<'s>>(source: &'s str, rust_object: &'s S) -> (u
     let end = offset + rust_object_source.len();
     (offset, end)
 }
+
+pub fn assert_name<'s>(emacs: &'s Token<'s>, name: &str) -> Result<(), Box<dyn std::error::Error>> {
+    let children = emacs.as_list()?;
+    let first_child = children
+        .first()
+        .ok_or("Should have at least one child.")?
+        .as_atom()?;
+    if first_child != name {
+        Err(format!(
+            "Expected a {expected} cell, but found a {found} cell.",
+            expected = name,
+            found = first_child
+        ))?;
+    }
+    Ok(())
+}