Add temporary visited_modules.with_incremented_index()

crates/next-api/src/app.rs

@@ -767,11 +767,16 @@ impl AppProject {
                     graphs.push(graph);
                     let is_layout =
                         module.server_path().file_stem().await?.as_deref() == Some("layout");
-                    if is_layout {
+                    visited_modules = if is_layout {
                         // Only propagate the visited_modules of the parent layout(s), not across
                         // siblings such as loading.js and page.js.
-                        visited_modules = visited_modules.concatenate(graph);
-                    }
+                        visited_modules.concatenate(graph)
+                    } else {
+                        // Prevents graph index from getting out of sync.
+                        // TODO We should remove VisitedModule entirely in favor of lookups in
+                        // SingleModuleGraph
+                        visited_modules.with_incremented_index()
+                    };
                 }
 
                 let graph =

turbopack/crates/turbopack-core/src/module_graph/mod.rs

@@ -82,6 +82,15 @@ impl VisitedModules {
         .cell())
     }
 
+    #[turbo_tasks::function]
+    pub async fn with_incremented_index(&self) -> Result<Vc<Self>> {
+        Ok(Self {
+            modules: self.modules.clone(),
+            next_graph_idx: self.next_graph_idx + 1,
+        }
+        .cell())
+    }
+
     #[turbo_tasks::function]
     pub async fn concatenate(&self, graph: Vc<SingleModuleGraph>) -> Result<Vc<Self>> {
         let graph = graph.await?;