From efea76beb0df3e23ecdac6fc8b3e5b1d3c5067f7 Mon Sep 17 00:00:00 2001
From: Patrik Oldsberg <poldsberg@gmail.com>
Date: Fri, 23 Jan 2026 13:52:47 +0100
Subject: [PATCH] frontend-app-api: filter out failed attachments

Signed-off-by: Patrik Oldsberg <poldsberg@gmail.com>
---
 .changeset/good-eggs-tell.md                  |  1 +
 .../src/tree/instantiateAppNodeTree.test.ts   | 49 +++++++++++++++++++
 .../src/tree/instantiateAppNodeTree.ts        | 28 ++++++-----
 3 files changed, 66 insertions(+), 12 deletions(-)

diff --git a/.changeset/good-eggs-tell.md b/.changeset/good-eggs-tell.md
index 86767c24a4..04ce63db7d 100644
--- a/.changeset/good-eggs-tell.md
+++ b/.changeset/good-eggs-tell.md
@@ -6,3 +6,4 @@ Updated error reporting and app tree resolution logic to attribute errors to the
 
 - If an attachment fails to provide the required input data, the error is now attributed to the attachment rather than the parent extension.
 - Singleton extension inputs will now only forward attachment errors if the input is required.
+- Array extension inputs will now filter out failed attachments instead of failing the entire app tree resolution.
diff --git a/packages/frontend-app-api/src/tree/instantiateAppNodeTree.test.ts b/packages/frontend-app-api/src/tree/instantiateAppNodeTree.test.ts
index d15873f5d1..485e9d95bd 100644
--- a/packages/frontend-app-api/src/tree/instantiateAppNodeTree.test.ts
+++ b/packages/frontend-app-api/src/tree/instantiateAppNodeTree.test.ts
@@ -1677,6 +1677,55 @@ describe('instantiateAppNodeTree', () => {
             },
           ]);
         });
+
+        it('should filter out failed attachments for non-singleton inputs', () => {
+          const node = makeNode(
+            resolveExtensionDefinition(
+              createExtension({
+                name: 'test',
+                attachTo: { id: 'ignored', input: 'ignored' },
+                inputs: {
+                  children: createExtensionInput([otherDataRef]),
+                },
+                output: [inputCountRef],
+                factory: ({ inputs }) => [
+                  inputCountRef(inputs.children.length),
+                ],
+              }),
+              { namespace: 'app' },
+            ),
+          );
+          expect(
+            createAppNodeInstance({
+              apis: testApis,
+              attachments: new Map([
+                [
+                  'children',
+                  [
+                    attachmentWithoutRequiredData,
+                    makeInstanceWithId(simpleExtension, {
+                      other: 42,
+                    }),
+                  ],
+                ],
+              ]),
+              node,
+              collector,
+            })?.getData(inputCountRef),
+          ).toBe(1);
+
+          expect(collector.collectErrors()).toEqual([
+            {
+              code: 'EXTENSION_INPUT_DATA_MISSING',
+              message:
+                "extension 'app/test' could not be attached because its output data ('test') does not match what the input 'children' requires ('other')",
+              context: {
+                node: attachmentWithoutRequiredData,
+                inputName: 'children',
+              },
+            },
+          ]);
+        });
       });
     });
   });
diff --git a/packages/frontend-app-api/src/tree/instantiateAppNodeTree.ts b/packages/frontend-app-api/src/tree/instantiateAppNodeTree.ts
index 55bea60274..ca0d785fee 100644
--- a/packages/frontend-app-api/src/tree/instantiateAppNodeTree.ts
+++ b/packages/frontend-app-api/src/tree/instantiateAppNodeTree.ts
@@ -38,21 +38,22 @@ const INSTANTIATION_FAILED = new Error('Instantiation failed');
 function mapWithFailures<T, U>(
   iterable: Iterable<T>,
   callback: (item: T) => U,
+  options?: { ignoreFailures?: boolean },
 ): U[] {
   let failed = false;
-  const results = Array.from(iterable).map(item => {
+  const results = [];
+  for (const item of iterable) {
     try {
-      return callback(item);
+      results.push(callback(item));
     } catch (error) {
       if (error === INSTANTIATION_FAILED) {
         failed = true;
       } else {
         throw error;
       }
-      return null as any;
     }
-  });
-  if (failed) {
+  }
+  if (failed && !options?.ignoreFailures) {
     throw INSTANTIATION_FAILED;
   }
   return results;
@@ -292,13 +293,16 @@ function resolveV2Inputs(
       }
     }
 
-    return mapWithFailures(attachedNodes, attachment =>
-      resolveInputDataContainer(
-        input.extensionData,
-        attachment,
-        inputName,
-        collector,
-      ),
+    return mapWithFailures(
+      attachedNodes,
+      attachment =>
+        resolveInputDataContainer(
+          input.extensionData,
+          attachment,
+          inputName,
+          collector,
+        ),
+      { ignoreFailures: true },
     );
   }) as ResolvedExtensionInputs<{ [inputName in string]: ExtensionInput }>;
 }