Update the new_breadcrumbs function to return an Option to prevent needlessly cloning the breadcrumbs when no new contexts are to be added.

src/renderer/renderer.rs

@@ -163,9 +163,15 @@ impl<'a> DustRenderer<'a> {
                 let val = walk_path(breadcrumbs, &container.path.keys);
                 match val {
                     Err(WalkError::CantWalk) => {
+                        let new_breadcrumbs = Self::new_breadcrumbs(
+                            breadcrumbs,
+                            None,
+                            &container.explicit_context,
+                            None,
+                        );
                         return self.render_maybe_body(
                             &container.else_contents,
-                            breadcrumbs,
+                            new_breadcrumbs.as_ref().unwrap_or(breadcrumbs),
                             blocks,
                         );
                     }
@@ -591,7 +597,14 @@ impl<'a> DustRenderer<'a> {
         injected_context: Option<&'b dyn ContextElement>,
         explicit_context: &Option<Path<'b>>,
         new_context_element: Option<&'b dyn ContextElement>,
-    ) -> Vec<&'b dyn ContextElement> {
+    ) -> Option<Vec<&'b dyn ContextElement>> {
+        // If none of the additional contexts are present, return None
+        // to signal that the original breadcrumbs should be used
+        // rather than incurring a copy here.
+        match (injected_context, explicit_context, new_context_element) {
+            (None, None, None) => return None,
+            _ => (),
+        };
         let mut new_stack = match explicit_context {
             Some(_) => Vec::with_capacity(3),
             None => breadcrumbs.clone(),
@@ -605,7 +618,7 @@ impl<'a> DustRenderer<'a> {
             });
         });
         new_context_element.map(|ctx| new_stack.push(ctx));
-        new_stack
+        Some(new_stack)
     }
 }