From 3c9a369908860b0c9c8d62442eaf4ea495334f08 Mon Sep 17 00:00:00 2001
From: Tom Alexander <tom@fizz.buzz>
Date: Sat, 30 May 2020 11:50:55 -0400
Subject: [PATCH] Skipping over pseudo contexts has fixed most of the tests.

---
 src/renderer/context_element.rs    | 10 ++++++++
 src/renderer/iteration_context.rs  |  4 +++
 src/renderer/parameters_context.rs |  4 +++
 src/renderer/walking.rs            | 39 +++++++++++++++++++++---------
 4 files changed, 46 insertions(+), 11 deletions(-)

diff --git a/src/renderer/context_element.rs b/src/renderer/context_element.rs
index 992fa6b..ec2e5a0 100644
--- a/src/renderer/context_element.rs
+++ b/src/renderer/context_element.rs
@@ -21,6 +21,16 @@ pub trait Truthiness {
 
 pub trait Walkable {
     fn walk(&self, segment: &str) -> Result<&dyn ContextElement, WalkError>;
+
+    /// If an element contains meta information and should not be
+    /// returned as the final result of a walk, this function should
+    /// return true.
+    ///
+    /// For example, the iteration context contains $idx and $len but
+    /// it should not be the result of a dot-reference like `{.}`.
+    fn is_pseudo_element(&self) -> bool {
+        false
+    }
 }
 
 pub trait Renderable {
diff --git a/src/renderer/iteration_context.rs b/src/renderer/iteration_context.rs
index acdd9a1..f6a3998 100644
--- a/src/renderer/iteration_context.rs
+++ b/src/renderer/iteration_context.rs
@@ -68,6 +68,10 @@ impl Walkable for IterationContext {
             _ => Err(WalkError::CantWalk),
         }
     }
+
+    fn is_pseudo_element(&self) -> bool {
+        true
+    }
 }
 
 impl CompareContextElement for IterationContext {
diff --git a/src/renderer/parameters_context.rs b/src/renderer/parameters_context.rs
index 7a3e6b1..1d4dd8b 100644
--- a/src/renderer/parameters_context.rs
+++ b/src/renderer/parameters_context.rs
@@ -103,6 +103,10 @@ impl Walkable for ParametersContext {
             OwnedRValue::RVLiteral(literal) => Ok(literal),
         }
     }
+
+    fn is_pseudo_element(&self) -> bool {
+        true
+    }
 }
 
 impl Clone for ParametersContext {
diff --git a/src/renderer/walking.rs b/src/renderer/walking.rs
index 49dff7f..58cd0b4 100644
--- a/src/renderer/walking.rs
+++ b/src/renderer/walking.rs
@@ -1,4 +1,5 @@
 use crate::renderer::context_element::ContextElement;
+use crate::renderer::context_element::Walkable;
 use crate::renderer::WalkError;
 use std::borrow::Borrow;
 
@@ -34,6 +35,17 @@ where
     WalkResult::FullyWalked(output)
 }
 
+pub fn get_first_non_pseudo_element<'a, B>(breadcrumbs: &'a Vec<B>) -> Option<&B>
+where
+    B: Borrow<dyn ContextElement + 'a>,
+{
+    breadcrumbs
+        .iter()
+        .rev()
+        .filter(|b| !(*b).borrow().is_pseudo_element())
+        .next()
+}
+
 pub fn walk_path<'a, B, P>(
     breadcrumbs: &'a Vec<B>,
     path: &Vec<P>,
@@ -60,17 +72,22 @@ where
         .borrow()
         == "."
     {
-        return match walk_path_from_single_level(
-            breadcrumbs
-                .last()
-                .expect("Breadcrumbs should never be empty"),
-            &path[1..],
-        ) {
-            // If no walking was done at all or we partially walked
-            // then stop trying to find anything because '.' restricts
-            // us to the current scope
-            WalkResult::NoWalk | WalkResult::PartialWalk => Err(WalkError::CantWalk),
-            WalkResult::FullyWalked(new_context) => Ok(new_context),
+        let first_non_pseudo_element = get_first_non_pseudo_element(breadcrumbs);
+        // println!(
+        //     "First non-pseudo element: {:?}",
+        //     first_non_pseudo_element.map(|b| b.borrow())
+        // );
+        return match first_non_pseudo_element {
+            None => Err(WalkError::CantWalk),
+            Some(current_context) => {
+                match walk_path_from_single_level(current_context, &path[1..]) {
+                    // If no walking was done at all or we partially walked
+                    // then stop trying to find anything because '.' restricts
+                    // us to the current scope
+                    WalkResult::NoWalk | WalkResult::PartialWalk => Err(WalkError::CantWalk),
+                    WalkResult::FullyWalked(new_context) => Ok(new_context),
+                }
+            }
         };
     }
     for context in breadcrumbs.iter().rev() {