feat(cli-internal): add lambda layer support to gen2-migration generate command

GEN2_MIGRATION_GUIDE.md

@@ -1051,7 +1051,7 @@ by the CLI setting that configures them.
       - 🔴 **function**
 
     - ⚠️ **Do you want to invoke this function on a recurring schedule**
-    - 🔴 **Do you want to enable Lambda layers for this function**
+    - 🟡 **Do you want to enable Lambda layers for this function** (_generate_ ✔ _refactor_ ✗)
     - 🟢 **Do you want to configure environment variables for this function**
     - 🟡 **Do you want to configure secret values this function can access** (_generate_ ✗ _refactor_ ✔)
     - ➤ **Choose the package manager that you want to use**

amplify-migration-apps/project-boards/_snapshot.post.generate/amplify/function/quotegenerator/resource.ts

@@ -8,5 +8,9 @@ export const quotegenerator = defineFunction({
   timeoutSeconds: 25,
   memoryMB: 128,
   environment: { ENV: `${branchName}`, REGION: 'us-east-1' },
+  layers: {
+    SharedUtils: 'arn:aws:lambda:us-east-1:123456789012:layer:SharedUtils:3',
+    CommonDeps: 'arn:aws:lambda:us-east-1:123456789012:layer:CommonDeps:1',
+  },
   runtime: 22,
 });

amplify-migration-apps/project-boards/_snapshot.pre.generate/amplify/#current-cloud-backend/function/quotegenerator/quotegenerator-cloudformation-template.json

@@ -79,7 +79,10 @@
           ]
         },
         "Runtime": "nodejs22.x",
-        "Layers": [],
+        "Layers": [
+          "arn:aws:lambda:us-east-1:123456789012:layer:SharedUtils:3",
+          "arn:aws:lambda:us-east-1:123456789012:layer:CommonDeps:1"
+        ],
         "Timeout": 25
       }
     },

amplify-migration-apps/project-boards/_snapshot.pre.generate/amplify/backend/function/quotegenerator/quotegenerator-cloudformation-template.json

@@ -79,7 +79,10 @@
           ]
         },
         "Runtime": "nodejs22.x",
-        "Layers": [],
+        "Layers": [
+          "arn:aws:lambda:us-east-1:123456789012:layer:SharedUtils:3",
+          "arn:aws:lambda:us-east-1:123456789012:layer:CommonDeps:1"
+        ],
         "Timeout": 25
       }
     },

amplify-migration-apps/project-boards/_snapshot.pre.refactor/amplify-projectboards-main-02940-functionquotegenerator-M4FF4RKY2IWJ.template.json

@@ -79,7 +79,10 @@
           ]
         },
         "Runtime": "nodejs22.x",
-        "Layers": [],
+        "Layers": [
+          "arn:aws:lambda:us-east-1:123456789012:layer:SharedUtils:3",
+          "arn:aws:lambda:us-east-1:123456789012:layer:CommonDeps:1"
+        ],
         "Timeout": 25
       }
     },

packages/amplify-cli/src/__tests__/commands/gen2-migration/_framework/clients/lambda.ts

@@ -99,6 +99,9 @@ export class LambdaMock {
           throw new Error(`Unexpected environment variable value for '${key}' in function '${resourceName}': ${value}`);
         }
 
+        const cfnLayers = template.Resources.LambdaFunction.Properties.Layers ?? [];
+        const layers = cfnLayers.map((arn: string) => ({ Arn: arn, CodeSize: 0 }));
+
         return {
           Configuration: {
             FunctionName: input.FunctionName,
@@ -108,6 +111,7 @@ export class LambdaMock {
             Environment: {
               Variables: envVariables,
             },
+            Layers: layers,
           },
           $metadata: {},
         };

packages/amplify-cli/src/__tests__/commands/gen2-migration/generate/amplify/function/function.generator.test.ts

@@ -1,5 +1,5 @@
 import ts from 'typescript';
-import { FunctionGenerator } from '../../../../../../commands/gen2-migration/generate/amplify/function/function.generator';
+import { FunctionGenerator, extractLayers } from '../../../../../../commands/gen2-migration/generate/amplify/function/function.generator';
 import { BackendGenerator } from '../../../../../../commands/gen2-migration/generate/amplify/backend.generator';
 import { RootPackageJsonGenerator } from '../../../../../../commands/gen2-migration/generate/package.json.generator';
 import { Gen1App } from '../../../../../../commands/gen2-migration/generate/_infra/gen1-app';
@@ -191,3 +191,66 @@ describe('FunctionGenerator', () => {
     });
   });
 });
+
+describe('extractLayers', () => {
+  it('returns undefined for undefined input', () => {
+    expect(extractLayers(undefined)).toBeUndefined();
+  });
+
+  it('returns undefined for an empty array', () => {
+    expect(extractLayers([])).toBeUndefined();
+  });
+
+  it('skips layers with missing Arn and returns undefined when no valid layers remain', () => {
+    expect(extractLayers([{ CodeSize: 100 }])).toBeUndefined();
+  });
+
+  it('skips layers with missing Arn while still extracting valid ones', () => {
+    const result = extractLayers([{ CodeSize: 100 }, { Arn: 'arn:aws:lambda:us-east-1:123456789012:layer:ValidLayer:1', CodeSize: 200 }]);
+    expect(result).toEqual({ ValidLayer: 'arn:aws:lambda:us-east-1:123456789012:layer:ValidLayer:1' });
+  });
+
+  it('throws on malformed ARN with too few segments', () => {
+    expect(() => extractLayers([{ Arn: 'arn:aws:lambda:us-east-1:123456789012:layer', CodeSize: 0 }])).toThrow(
+      'Malformed Lambda layer ARN (expected at least 8 colon-delimited segments)',
+    );
+  });
+
+  it('throws when ARN resource type is not "layer"', () => {
+    expect(() => extractLayers([{ Arn: 'arn:aws:lambda:us-east-1:123456789012:function:myFunc:1', CodeSize: 0 }])).toThrow(
+      "Expected Lambda layer ARN but got resource type 'function'",
+    );
+  });
+
+  it('throws on duplicate layer names with a descriptive message', () => {
+    expect(() =>
+      extractLayers([
+        { Arn: 'arn:aws:lambda:us-east-1:111111111111:layer:SharedUtils:1', CodeSize: 0 },
+        { Arn: 'arn:aws:lambda:us-east-1:222222222222:layer:SharedUtils:2', CodeSize: 0 },
+      ]),
+    ).toThrow("Duplicate layer name 'SharedUtils' detected");
+  });
+
+  it('extracts up to 5 layers (AWS maximum)', () => {
+    const layers = Array.from({ length: 5 }, (_, i) => ({
+      Arn: `arn:aws:lambda:us-east-1:123456789012:layer:Layer${i}:1`,
+      CodeSize: i * 100,
+    }));
+    const result = extractLayers(layers);
+    expect(Object.keys(result!)).toHaveLength(5);
+    for (let i = 0; i < 5; i++) {
+      expect(result![`Layer${i}`]).toBe(`arn:aws:lambda:us-east-1:123456789012:layer:Layer${i}:1`);
+    }
+  });
+
+  it('extracts layer name and full ARN in the happy path', () => {
+    const result = extractLayers([
+      { Arn: 'arn:aws:lambda:us-east-1:123456789012:layer:SharedUtils:3', CodeSize: 1024 },
+      { Arn: 'arn:aws:lambda:us-east-1:123456789012:layer:CommonDeps:1', CodeSize: 2048 },
+    ]);
+    expect(result).toEqual({
+      SharedUtils: 'arn:aws:lambda:us-east-1:123456789012:layer:SharedUtils:3',
+      CommonDeps: 'arn:aws:lambda:us-east-1:123456789012:layer:CommonDeps:1',
+    });
+  });
+});

packages/amplify-cli/src/commands/gen2-migration/generate/amplify/function/function.generator.ts

@@ -39,6 +39,12 @@ interface ResolvedFunction {
   readonly runtime?: string;
   readonly schedule?: string;
   readonly environment?: Readonly<Record<string, string>>;
+  /**
+   * Lambda layer ARNs keyed by the layer name extracted from the ARN.
+   * Undefined when the function has no attached layers.
+   */
+  readonly layers?: Readonly<Record<string, string>>;
+
   readonly escapeHatches: readonly EnvVarEscapeHatch[];
   readonly dynamoActions: readonly string[];
   readonly kinesisActions: readonly string[];
@@ -175,6 +181,8 @@ export class FunctionGenerator implements Planner {
     // Extract DynamoDB/Kinesis actions and GraphQL API permissions from the function's CloudFormation template
     const { dynamoActions, kinesisActions, graphqlApiPermissions, authAccess } = this.extractCfnPermissions();
 
+    const layers = extractLayers(config.Layers);
+
     return {
       resourceName: this.resource.resourceName,
       category: this.category,
@@ -185,6 +193,7 @@ export class FunctionGenerator implements Planner {
       runtime,
       schedule,
       environment: Object.keys(retained).length > 0 ? retained : undefined,
+      layers,
       escapeHatches,
       dynamoActions,
       kinesisActions,
@@ -208,6 +217,7 @@ export class FunctionGenerator implements Planner {
       runtime: func.runtime,
       schedule: func.schedule,
       environment: func.environment,
+      layers: func.layers,
     };
 
     const nodes = this.renderer.render(renderOpts);
@@ -862,6 +872,56 @@ function classifyEnvVars(variables: Record<string, string>): {
   return { retained, escapeHatches };
 }
 
+/**
+ * Extracts Lambda layer ARNs into a `Record<string, string>` for use in
+ * `defineFunction({ layers })`.
+ *
+ * The key is the layer name parsed from the ARN (e.g. `SharedUtils`), and
+ * the value is the full layer version ARN. Layers with missing ARNs are
+ * skipped.
+ *
+ * @param sdkLayers - The `Layers` array from `FunctionConfiguration`.
+ * @returns A layers record, or `undefined` if no valid layers exist.
+ * @throws Error if an ARN is malformed, not a layer ARN, or if two layers
+ *   share the same name.
+ */
+export function extractLayers(
+  sdkLayers: ReadonlyArray<{ Arn?: string; CodeSize?: number }> | undefined,
+): Readonly<Record<string, string>> | undefined {
+  if (!sdkLayers || sdkLayers.length === 0) return undefined;
+
+  const result: Record<string, string> = {};
+  for (const layer of sdkLayers) {
+    if (!layer.Arn) continue;
+
+    // ARN format: arn:aws:lambda:<region>:<account>:layer:<layerName>:<version>
+    const parts = layer.Arn.split(':');
+    if (parts.length < 8) {
+      throw new Error(`Malformed Lambda layer ARN (expected at least 8 colon-delimited segments): ${layer.Arn}`);
+    }
+    if (parts[5] !== 'layer') {
+      throw new Error(`Expected Lambda layer ARN but got resource type '${parts[5]}': ${layer.Arn}`);
+    }
+
+    const layerName = parts[6];
+    if (!layerName) {
+      throw new Error(`Lambda layer ARN missing layer name: ${layer.Arn}`);
+    }
+
+    if (result[layerName]) {
+      throw new Error(
+        `Duplicate layer name '${layerName}' detected. ` +
+          `Existing: ${result[layerName]}, New: ${layer.Arn}. ` +
+          `Manual resolution required — rename one layer key in the Gen2 defineFunction() output.`,
+      );
+    }
+
+    result[layerName] = layer.Arn;
+  }
+
+  return Object.keys(result).length > 0 ? result : undefined;
+}
+
 /**
  * Creates `backend.functionName.addEnvironment(name, expression)`.
  */

packages/amplify-cli/src/commands/gen2-migration/generate/amplify/function/function.renderer.ts

@@ -15,6 +15,11 @@ export interface RenderDefineFunctionOptions {
   readonly runtime?: string;
   readonly schedule?: string;
   readonly environment?: Readonly<Record<string, string>>;
+  /**
+   * Lambda layer ARNs keyed by the layer name extracted from the ARN.
+   * Undefined when the function has no attached layers.
+   */
+  readonly layers?: Readonly<Record<string, string>>;
 }
 
 /**
@@ -69,6 +74,9 @@ export class FunctionRenderer {
     // environment
     this.renderEnvironment(properties, namedImports, opts);
 
+    // layers
+    this.renderLayers(properties, opts.layers);
+
     // runtime
     this.renderRuntime(properties, opts.runtime);
 
@@ -135,6 +143,16 @@ export class FunctionRenderer {
       target.push(factory.createPropertyAssignment('schedule', factory.createStringLiteral(converted)));
     }
   }
+
+  private renderLayers(target: ObjectLiteralElementLike[], layers?: Readonly<Record<string, string>>): void {
+    if (!layers || Object.keys(layers).length === 0) return;
+
+    const layerProps = Object.entries(layers).map(([key, value]) =>
+      factory.createPropertyAssignment(factory.createStringLiteral(key), factory.createStringLiteral(value)),
+    );
+
+    target.push(factory.createPropertyAssignment('layers', factory.createObjectLiteralExpression(layerProps, true)));
+  }
 }
 
 /**