frontend-app-api: switch undeclared inputs to be a warning instead of error

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

.changeset/silver-countries-notice.md

@@ -0,0 +1,5 @@
+---
+'@backstage/frontend-app-api': minor
+---
+
+Attaching extensions to an input that does not exist is now a warning rather than an error.

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

@@ -30,6 +30,7 @@ import { AppNodeSpec } from '@backstage/frontend-plugin-api';
 import { resolveAppTree } from './resolveAppTree';
 // eslint-disable-next-line @backstage/no-relative-monorepo-imports
 import { resolveExtensionDefinition } from '../../../frontend-plugin-api/src/wiring/resolveExtensionDefinition';
+import { withLogCollector } from '@backstage/test-utils';
 
 const testDataRef = createExtensionDataRef<string>('test');
 const otherDataRef = createExtensionDataRef<number>('other');
@@ -433,8 +434,8 @@ describe('createAppNodeInstance', () => {
     );
   });
 
-  it('should refuse to create an instance with undeclared inputs', () => {
-    expect(() =>
+  it('should warn when creating an instance with undeclared inputs', () => {
+    const { warn } = withLogCollector(['warn'], () =>
       createAppNodeInstance({
         attachments: new Map([
           [
@@ -458,7 +459,7 @@ describe('createAppNodeInstance', () => {
           resolveExtensionDefinition(
             createExtension({
               namespace: 'app',
-              name: 'test',
+              name: 'parent',
               attachTo: { id: 'ignored', input: 'ignored' },
               inputs: {
                 declared: createExtensionInput({
@@ -471,13 +472,15 @@ describe('createAppNodeInstance', () => {
           ),
         ),
       }),
-    ).toThrow(
-      "Failed to instantiate extension 'app/test', received undeclared input 'undeclared' from extension 'app/test'",
     );
+
+    expect(warn).toEqual([
+      "The extension 'app/test' is attached to the input 'undeclared' of 'app/parent', but the extension 'app/parent' noes not declare a 'undeclared' input",
+    ]);
   });
 
   it('should refuse to create an instance with multiple undeclared inputs', () => {
-    expect(() =>
+    const { warn } = withLogCollector(['warn'], () =>
       createAppNodeInstance({
         attachments: new Map([
           [
@@ -496,7 +499,7 @@ describe('createAppNodeInstance', () => {
           resolveExtensionDefinition(
             createExtension({
               namespace: 'app',
-              name: 'test',
+              name: 'parent',
               attachTo: { id: 'ignored', input: 'ignored' },
               output: {},
               factory: () => ({}),
@@ -504,9 +507,12 @@ describe('createAppNodeInstance', () => {
           ),
         ),
       }),
-    ).toThrow(
-      "Failed to instantiate extension 'app/test', received undeclared inputs 'undeclared1' from extension 'app/test' and 'undeclared2' from extensions 'app/test', 'app/test'",
     );
+
+    expect(warn).toEqual([
+      "The extension 'app/test' is attached to the input 'undeclared1' of 'app/parent', but the extension 'app/parent' noes not declare a 'undeclared1' input",
+      "The extensions 'app/test', 'app/test' are attached to the input 'undeclared2' of 'app/parent', but the extension 'app/parent' noes not declare a 'undeclared2' input",
+    ]);
   });
 
   it('should refuse to create an instance with multiple inputs for required singleton', () => {

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

@@ -46,26 +46,26 @@ function resolveInputData(
 }
 
 function resolveInputs(
+  id: string,
   inputMap: AnyExtensionInputMap,
   attachments: ReadonlyMap<string, AppNode[]>,
 ): ResolvedExtensionInputs<AnyExtensionInputMap> {
   const undeclaredAttachments = Array.from(attachments.entries()).filter(
     ([inputName]) => inputMap[inputName] === undefined,
   );
-  // TODO: Make this a warning rather than an error
-  if (undeclaredAttachments.length > 0) {
-    throw new Error(
-      `received undeclared input${
-        undeclaredAttachments.length > 1 ? 's' : ''
-      } ${undeclaredAttachments
-        .map(
-          ([k, exts]) =>
-            `'${k}' from extension${exts.length > 1 ? 's' : ''} '${exts
-              .map(e => e.spec.id)
-              .join("', '")}'`,
-        )
-        .join(' and ')}`,
-    );
+
+  if (process.env.NODE_ENV !== 'production') {
+    for (const [name, nodes] of undeclaredAttachments) {
+      const pl = nodes.length > 1;
+      // eslint-disable-next-line no-console
+      console.warn(
+        `The extension${pl ? 's' : ''} '${nodes
+          .map(n => n.spec.id)
+          .join("', '")}' ${
+          pl ? 'are' : 'is'
+        } attached to the input '${name}' of '${id}', but the extension '${id}' noes not declare a '${name}' input`,
+      );
+    }
   }
 
   return mapValues(inputMap, (input, inputName) => {
@@ -129,7 +129,7 @@ export function createAppNodeInstance(options: {
     const namedOutputs = internalExtension.factory({
       node,
       config: parsedConfig,
-      inputs: resolveInputs(internalExtension.inputs, attachments),
+      inputs: resolveInputs(id, internalExtension.inputs, attachments),
     });
 
     for (const [name, output] of Object.entries(namedOutputs)) {