All but explicit context for new_breadcrumbs_section.

src/renderer/tree_renderer.rs

@@ -44,6 +44,15 @@ impl<'a> DustRenderer<'a> {
             .insert(template.name.clone(), &template.template);
     }
 
+    /// Returns a option of a tuple of (parent, new_node_elements)
+    /// which can then be formed into new BreadcrumbTreeNodes
+    ///
+    /// If None is returned, then it is a signal to simply re-use the
+    /// existing breadcrumbs.
+    ///
+    /// Otherwise, the parent (which may be None, especially for
+    /// explicit contexts) and the additional node elements (which may
+    /// be empty) should be combined into a final BreadcrumbTreeNode
     fn new_breadcrumbs_section<'b>(
         &self,
         maybe_breadcrumbs: Option<&'a BreadcrumbTreeNode>,
@@ -51,15 +60,20 @@ impl<'a> DustRenderer<'a> {
         injected_context: Option<&'b dyn IntoContextElement>,
         explicit_context: &Option<Path<'b>>,
         new_context_element: Option<&'b dyn ContextElement>,
-    ) -> Option<&'a BreadcrumbTreeNode> {
-        // If there is no new content, return the original breadcrumbs
+    ) -> Option<(
+        Option<&'b BreadcrumbTreeNode>,
+        Vec<BreadcrumbTreeNodeElement<'b>>,
+    )> {
+        // 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 (
             index_context,
             injected_context,
             explicit_context,
             new_context_element,
         ) {
-            (None, None, None, None) => return maybe_breadcrumbs,
+            (None, None, None, None) => return None,
             _ => (),
         }
 
@@ -69,17 +83,18 @@ impl<'a> DustRenderer<'a> {
             Some(_) => None,
             None => maybe_breadcrumbs,
         };
-        let mut new_stack = None;
+        let mut new_nodes = Vec::new();
 
         // TODO: Explicit context
 
-        injected_context.map(|ctx| {
-            new_stack = Some(BreadcrumbTreeNode::new(
-                parent.map(|b| b as _),
-                BreadcrumbTreeNodeElement::Borrowed(ctx),
+        injected_context.map(|ctx| new_nodes.push(BreadcrumbTreeNodeElement::Borrowed(ctx)));
+        new_context_element.map(|ctx| {
+            new_nodes.push(BreadcrumbTreeNodeElement::Borrowed(
+                ctx.from_context_element(),
             ))
         });
+        index_context.map(|ctx| new_nodes.push(BreadcrumbTreeNodeElement::Borrowed(ctx)));
 
-        None
+        Some((parent, new_nodes))
     }
 }