feat(gen2-migration): allow generate to skip non-JS Lambda functions (#14744)

iliapolo · web-flow · commit 64edeeb975da · 2026-04-02T17:25:04.000-04:00
feat(cli-internal): allow generate to skip non-JS Lambda functions

Surface non-JS Lambda runtimes as unsupported in the assessment
rather than throwing at generation time. The FunctionAssessor now
reads the runtime from the local CloudFormation template and marks
the resource as unsupported for generate when it is not Node.js.

The generate orchestrator checks assessment.of(resource, step)
before entering the switch, skipping any resource that is not
supported. This means --skip-validations allows generation to
proceed while silently skipping non-JS functions.

Also adds Assessment.of(resource, step) which returns the support
level for a specific resource, usable by any step orchestrator.

Tested with unit tests covering Python, Java, dotnet runtimes,
Node.js as supported, and missing template as an error.
---
Prompt: Fix issue 14723 — `generate` should allow skipping
over non JS functions. These functions can later be hand coded
by the user. Instead of throwing an error, surface the
unsupported functions as part of the assessment validation —
this would allow --skip-validations to skip over this as well.
diff --git a/docs/packages/amplify-cli/src/commands/gen2-migration/assess.md b/docs/packages/amplify-cli/src/commands/gen2-migration/assess.md
@@ -45,7 +45,7 @@ Standalone class (not a step). `assess()` returns an `Assessment` instance. `run
 
 [`src/commands/gen2-migration/assess/assessment.ts`](../../../../packages/amplify-cli/src/commands/gen2-migration/assess/assessment.ts)
 
-Collector that assessors contribute to. Exposes `validFor('generate' | 'refactor')` for step validation, and `render()` for terminal output. Each entry uses the `Support` type with `level` and optional `note`.
+Collector that assessors contribute to. Exposes `validFor('generate' | 'refactor')` for step validation, `of(resource, step)` for per-resource support lookup, and `render()` for terminal output. Each entry uses the `Support` type with `level` and optional `note`.
 
 ### `Support`
 
@@ -70,22 +70,23 @@ Produced by `Gen1App.discover()`. The `key` field is a typed `category:service`
 
 ## Supported Resources
 
-| Category  | Service                 | Generate | Refactor    |
-| --------- | ----------------------- | -------- | ----------- |
-| auth      | Cognito                 | ✔        | ✔           |
-| auth      | Cognito-UserPool-Groups | ✔        | ✔           |
-| storage   | S3                      | ✔        | ✔           |
-| storage   | DynamoDB                | ✔        | ✔           |
-| api       | AppSync                 | ✔        | n/a         |
-| api       | API Gateway             | ✔        | n/a         |
-| analytics | Kinesis                 | ✔        | ✔           |
-| function  | Lambda                  | ✔        | ✔           |
-| geo       | Map                     | ✔        | ✔           |
-| geo       | PlaceIndex              | ✔        | ✔           |
-| geo       | GeofenceCollection      | ✔        | unsupported |
+| Category  | Service                 | Generate         | Refactor    |
+| --------- | ----------------------- | ---------------- | ----------- |
+| auth      | Cognito                 | ✔                | ✔           |
+| auth      | Cognito-UserPool-Groups | ✔                | ✔           |
+| storage   | S3                      | ✔                | ✔           |
+| storage   | DynamoDB                | ✔                | ✔           |
+| api       | AppSync                 | ✔                | n/a         |
+| api       | API Gateway             | ✔                | n/a         |
+| analytics | Kinesis                 | ✔                | ✔           |
+| function  | Lambda                  | ✔ (Node.js only) | ✔           |
+| geo       | Map                     | ✔                | ✔           |
+| geo       | PlaceIndex              | ✔                | ✔           |
+| geo       | GeofenceCollection      | ✔                | unsupported |
 
 ## AI Development Notes
 
 - Adding a new resource type: add the pair to `KNOWN_RESOURCE_KEYS` in `gen1-app.ts`, create an assessor, handle the case in `assess.ts`, and in the generate/refactor steps. The compiler enforces exhaustiveness.
-- The `Assessment` is also used by generate and refactor steps for validation — `validFor(step)` returns false if any resource or feature is unsupported for that step.
+- The `Assessment` is also used by generate and refactor steps for validation — `validFor(step)` returns false if any resource or feature is unsupported for that step. The `of(resource, step)` method returns the `Support` for a specific resource, used by the generate orchestrator to skip unsupported resources before instantiating generators.
 - Feature detection (overrides, custom policies) is assessor-specific. Each assessor checks for files in the cloud backend directory via `gen1App.fileExists()`.
+- `FunctionAssessor` reads the Lambda runtime from the local CloudFormation template (`function/<name>/<name>-cloudformation-template.json`). Non-Node.js runtimes are marked as unsupported for generate, allowing `--skip-validations` to skip them.
diff --git a/docs/packages/amplify-cli/src/commands/gen2-migration/generate.md b/docs/packages/amplify-cli/src/commands/gen2-migration/generate.md
@@ -69,10 +69,12 @@ The pipeline has two layers plus an orchestrator:
 - **Orchestrator** (`generate.ts`) — Uses `Gen1App.discover()` to iterate
   all resources from `amplify-meta.json`, dispatches by `resource.key`
   (a typed `ResourceKey`) via an exhaustive switch statement, and
-  instantiates one generator per resource. Collects all operations and
-  appends final operations for folder replacement + npm install. The same
-  switch is used by the `assess()` method to record support into an
-  `Assessment` collector.
+  instantiates one generator per resource. Resources marked as unsupported
+  by the assessment are skipped before the switch — no generator is
+  instantiated for them. Collects all operations and appends final
+  operations for folder replacement + npm install. The same switch is used
+  by the `assess()` method to record support into an `Assessment`
+  collector.
 
 ## Key Abstractions
 
diff --git a/packages/amplify-cli/src/__tests__/commands/gen2-migration/assess.test.ts b/packages/amplify-cli/src/__tests__/commands/gen2-migration/assess.test.ts
@@ -14,6 +14,10 @@ function mockGen1App(resources: DiscoveredResource[], existingFiles: string[] =
   } as unknown as Gen1App;
 }
 
+const NODEJS_TEMPLATE = {
+  Resources: { LambdaFunction: { Properties: { Runtime: 'nodejs18.x' } } },
+};
+
 describe('AmplifyMigrationAssessor', () => {
   describe('assess()', () => {
     it('returns empty assessment when no resources discovered', () => {
@@ -31,7 +35,10 @@ describe('AmplifyMigrationAssessor', () => {
       const gen1App = mockGen1App(
         [{ category: 'function', resourceName: 'myFunc', service: 'Lambda', key: 'function:Lambda' }],
         ['function/myFunc/custom-policies.json'],
-        { 'function/myFunc/custom-policies.json': [{ Action: ['s3:GetObject'], Resource: ['arn:aws:s3:::my-bucket/*'] }] },
+        {
+          'function/myFunc/myFunc-cloudformation-template.json': NODEJS_TEMPLATE,
+          'function/myFunc/custom-policies.json': [{ Action: ['s3:GetObject'], Resource: ['arn:aws:s3:::my-bucket/*'] }],
+        },
       );
       const assessor = new AmplifyMigrationAssessor(gen1App);
       const assessment = assessor.assess();
@@ -56,7 +63,10 @@ describe('AmplifyMigrationAssessor', () => {
       const gen1App = mockGen1App(
         [{ category: 'function', resourceName: 'myFunc', service: 'Lambda', key: 'function:Lambda' }],
         ['function/myFunc/custom-policies.json'],
-        { 'function/myFunc/custom-policies.json': [{ Action: [], Resource: [] }] },
+        {
+          'function/myFunc/myFunc-cloudformation-template.json': NODEJS_TEMPLATE,
+          'function/myFunc/custom-policies.json': [{ Action: [], Resource: [] }],
+        },
       );
       const assessor = new AmplifyMigrationAssessor(gen1App);
       const assessment = assessor.assess();
@@ -73,6 +83,26 @@ describe('AmplifyMigrationAssessor', () => {
       expect(assessment.resources[0].generate.level).toBe('unsupported');
       expect(assessment.resources[0].refactor.level).toBe('unsupported');
     });
+
+    it('marks function with non-JS runtime as unsupported for generate', () => {
+      const gen1App = mockGen1App(
+        [{ category: 'function', resourceName: 'myPythonFunc', service: 'Lambda', key: 'function:Lambda' }],
+        ['function/myPythonFunc/myPythonFunc-cloudformation-template.json'],
+        {
+          'function/myPythonFunc/myPythonFunc-cloudformation-template.json': {
+            Resources: { LambdaFunction: { Properties: { Runtime: 'python3.11' } } },
+          },
+        },
+      );
+      const assessor = new AmplifyMigrationAssessor(gen1App);
+      const assessment = assessor.assess();
+
+      expect(assessment.resources).toHaveLength(1);
+      expect(assessment.resources[0].generate.level).toBe('unsupported');
+      expect(assessment.resources[0].refactor.level).toBe('supported');
+      expect(assessment.validFor('generate')).toBe(false);
+      expect(assessment.validFor('refactor')).toBe(true);
+    });
   });
 
   describe('run()', () => {
diff --git a/packages/amplify-cli/src/__tests__/commands/gen2-migration/assess/function/function.assessor.test.ts b/packages/amplify-cli/src/__tests__/commands/gen2-migration/assess/function/function.assessor.test.ts
@@ -10,12 +10,18 @@ function mockGen1App(existingFiles: string[] = [], jsonFiles: Record<string, unk
   } as unknown as Gen1App;
 }
 
+const NODEJS_TEMPLATE_PATH = 'function/myFunc/myFunc-cloudformation-template.json';
+const NODEJS_TEMPLATE = {
+  Resources: { LambdaFunction: { Properties: { Runtime: 'nodejs18.x' } } },
+};
+
 const RESOURCE: DiscoveredResource = { category: 'function', resourceName: 'myFunc', service: 'Lambda', key: 'function:Lambda' };
 
 describe('FunctionAssessor', () => {
   it('records resource as supported', () => {
+    const gen1App = mockGen1App([], { [NODEJS_TEMPLATE_PATH]: NODEJS_TEMPLATE });
     const assessment = new Assessment('app', 'dev');
-    new FunctionAssessor(mockGen1App(), RESOURCE).record(assessment);
+    new FunctionAssessor(gen1App, RESOURCE).record(assessment);
 
     const entry = assessment.resources[0];
     expect(entry!.generate.level).toBe('supported');
@@ -24,6 +30,7 @@ describe('FunctionAssessor', () => {
 
   it('detects non-empty custom-policies.json', () => {
     const gen1App = mockGen1App(['function/myFunc/custom-policies.json'], {
+      [NODEJS_TEMPLATE_PATH]: NODEJS_TEMPLATE,
       'function/myFunc/custom-policies.json': [{ Action: ['s3:GetObject'], Resource: ['arn:aws:s3:::bucket/*'] }],
     });
     const assessment = new Assessment('app', 'dev');
@@ -39,6 +46,7 @@ describe('FunctionAssessor', () => {
 
   it('ignores empty custom-policies.json', () => {
     const gen1App = mockGen1App(['function/myFunc/custom-policies.json'], {
+      [NODEJS_TEMPLATE_PATH]: NODEJS_TEMPLATE,
       'function/myFunc/custom-policies.json': [{ Action: [], Resource: [] }],
     });
     const assessment = new Assessment('app', 'dev');
@@ -48,9 +56,45 @@ describe('FunctionAssessor', () => {
   });
 
   it('records no features when custom-policies.json is absent', () => {
+    const gen1App = mockGen1App([], { [NODEJS_TEMPLATE_PATH]: NODEJS_TEMPLATE });
     const assessment = new Assessment('app', 'dev');
-    new FunctionAssessor(mockGen1App(), RESOURCE).record(assessment);
+    new FunctionAssessor(gen1App, RESOURCE).record(assessment);
 
     expect(assessment.features).toHaveLength(0);
   });
+
+  describe('non-JS runtime detection', () => {
+    it('marks resource as unsupported for generate when runtime is Python', () => {
+      const gen1App = mockGen1App([], {
+        [NODEJS_TEMPLATE_PATH]: { Resources: { LambdaFunction: { Properties: { Runtime: 'python3.11' } } } },
+      });
+      const assessment = new Assessment('app', 'dev');
+      new FunctionAssessor(gen1App, RESOURCE).record(assessment);
+
+      const entry = assessment.resources[0];
+      expect(entry!.generate.level).toBe('unsupported');
+      expect(entry!.generate.note).toContain('python3.11');
+      expect(entry!.refactor.level).toBe('supported');
+    });
+
+    it('fails assessment validFor generate when runtime is non-JS', () => {
+      const gen1App = mockGen1App([], {
+        [NODEJS_TEMPLATE_PATH]: { Resources: { LambdaFunction: { Properties: { Runtime: 'dotnet8' } } } },
+      });
+      const assessment = new Assessment('app', 'dev');
+      new FunctionAssessor(gen1App, RESOURCE).record(assessment);
+
+      expect(assessment.validFor('generate')).toBe(false);
+      expect(assessment.validFor('refactor')).toBe(true);
+    });
+
+    it('treats nodejs runtimes as supported', () => {
+      const gen1App = mockGen1App([], { [NODEJS_TEMPLATE_PATH]: NODEJS_TEMPLATE });
+      const assessment = new Assessment('app', 'dev');
+      new FunctionAssessor(gen1App, RESOURCE).record(assessment);
+
+      expect(assessment.resources[0]!.generate.level).toBe('supported');
+      expect(assessment.features).toHaveLength(0);
+    });
+  });
 });
diff --git a/packages/amplify-cli/src/__tests__/commands/gen2-migration/generate.test.ts b/packages/amplify-cli/src/__tests__/commands/gen2-migration/generate.test.ts
@@ -152,5 +152,28 @@ describe('AmplifyMigrationGenerateStep', () => {
       lockSpy.mockRestore();
       wdSpy.mockRestore();
     });
+
+    it('skips unsupported resources without instantiating generators', async () => {
+      const gen1 = mockGen1App({
+        discover: () => [{ category: 'function', resourceName: 'myPythonFunc', service: 'Lambda', key: 'function:Lambda' as const }],
+        json: (p: string) => {
+          if (p.endsWith('-cloudformation-template.json')) {
+            return { Resources: { LambdaFunction: { Properties: { Runtime: 'python3.11' } } } };
+          }
+          return undefined;
+        },
+      });
+      const logger = new SpinningLogger('generate', { debug: true });
+
+      const plan = await new AmplifyMigrationGenerateStep(logger, gen1, {} as $TSContext, {} as AmplifyGen2MigrationValidations).forward();
+
+      // 3 validation ops (lock, working dir, assessment)
+      // 1 delete amplify dir
+      // 6 infrastructure generators (backend, root package.json, backend package.json, tsconfig, amplify.yml, gitignore)
+      // 2 post-generation ops (replace folder, install deps)
+      // = 12 total — the unsupported function contributes zero operations.
+      // eslint-disable-next-line @typescript-eslint/no-explicit-any -- accessing private field to assert operation count
+      expect((plan as any).operations).toHaveLength(12);
+    });
   });
 });
diff --git a/packages/amplify-cli/src/commands/gen2-migration/assess/assessment.ts b/packages/amplify-cli/src/commands/gen2-migration/assess/assessment.ts
@@ -98,6 +98,25 @@ export class Assessment {
     return this._features;
   }
 
+  /**
+   * Returns the support level for a specific resource in the given step.
+   */
+  // eslint-disable-next-line consistent-return -- exhaustive switch; compiler enforces all cases
+  public of(resource: DiscoveredResource, step: 'generate' | 'refactor'): Support {
+    const entry = this._resources.find(
+      (ra) => ra.resource.category === resource.category && ra.resource.resourceName === resource.resourceName,
+    );
+    if (!entry) {
+      throw new Error(`No assessment recorded for resource '${resource.category}/${resource.resourceName}'`);
+    }
+    switch (step) {
+      case 'generate':
+        return entry.generate;
+      case 'refactor':
+        return entry.refactor;
+    }
+  }
+
   /**
    * Returns true if all resources and features are supported for the given step.
    */
diff --git a/packages/amplify-cli/src/commands/gen2-migration/assess/function/function.assessor.ts b/packages/amplify-cli/src/commands/gen2-migration/assess/function/function.assessor.ts
@@ -4,7 +4,7 @@ import { Gen1App, DiscoveredResource, KNOWN_FEATURES } from '../../generate/_inf
 
 /**
  * Assesses migration readiness for a single Lambda function resource.
- * Detects custom-policies.json usage.
+ * Detects non-JS runtimes and custom-policies.json usage.
  */
 export class FunctionAssessor implements Assessor {
   public constructor(private readonly gen1App: Gen1App, private readonly resource: DiscoveredResource) {}
@@ -13,9 +13,13 @@ export class FunctionAssessor implements Assessor {
    * Records resource-level and feature-level support for this function.
    */
   public record(assessment: Assessment): void {
+    const templatePath = `function/${this.resource.resourceName}/${this.resource.resourceName}-cloudformation-template.json`;
+    const template = this.gen1App.json(templatePath);
+    const runtime = template.Resources.LambdaFunction.Properties.Runtime;
+
     assessment.recordResource({
       resource: this.resource,
-      generate: supported(),
+      generate: this.isNonJsRuntime(runtime) ? unsupported(`uses non-JS runtime '${runtime}'`) : supported(),
       refactor: supported(),
     });
 
@@ -30,6 +34,13 @@ export class FunctionAssessor implements Assessor {
     }
   }
 
+  /**
+   * Returns true if the runtime is present and is not a Node.js variant.
+   */
+  private isNonJsRuntime(runtime: string): boolean {
+    return !runtime.startsWith('nodejs');
+  }
+
   /**
    * Returns true if the function has non-empty custom policies.
    * The file always exists but defaults to `[{"Action":[],"Resource":[]}]`.
diff --git a/packages/amplify-cli/src/commands/gen2-migration/generate.ts b/packages/amplify-cli/src/commands/gen2-migration/generate.ts
@@ -71,6 +71,12 @@ export class AmplifyMigrationGenerateStep extends AmplifyMigrationStep {
     const discovered = this.gen1App.discover();
 
     for (const resource of discovered) {
+      // skip resources the assessment did not mark as supported.
+      // these will show up as validation errors the user has to acknowledge.
+      if (assessment.of(resource, 'generate').level !== 'supported') {
+        continue;
+      }
+
       switch (resource.key) {
         case 'auth:Cognito': {
           const isReferenceAuth = discovered
