frontend-app-api: no longer error on invalid disabled inputs

Signed-off-by: Patrik Oldsberg <poldsberg@gmail.com>

.changeset/selfish-flies-kneel.md

@@ -0,0 +1,5 @@
+---
+'@backstage/frontend-app-api': patch
+---
+
+No longer throw error on invalid input if the child is disabled.

packages/frontend-app-api/src/tree/instantiateAppNodeTree.test.ts

@@ -167,7 +167,8 @@ describe('instantiateAppNodeTree', () => {
       {
         ...makeSpec(simpleExtension),
         id: 'child-node',
-        attachTo: { id: 'root-node', input: 'test' },
+        // Using an invalid input should not be an error when disabled
+        attachTo: { id: 'root-node', input: 'invalid' },
         disabled: true,
       },
     ]);

packages/frontend-app-api/src/tree/instantiateAppNodeTree.ts

@@ -176,7 +176,9 @@ export function instantiateAppNodeTree(rootNode: AppNode): void {
         }
         return [{ id: child.spec.id, instance: childInstance }];
       });
-      instantiatedAttachments.set(input, instantiatedChildren);
+      if (instantiatedChildren.length > 0) {
+        instantiatedAttachments.set(input, instantiatedChildren);
+      }
     }
 
     (node as Mutable<AppNode>).instance = createAppNodeInstance({