fix(lambda): fromDockerBuild output is located under /asset

packages/@aws-cdk/aws-lambda/lib/code.ts

@@ -67,9 +67,19 @@ export abstract class Code {
    * @param options Docker build options
    */
   public static fromDockerBuild(path: string, options: DockerBuildAssetOptions = {}): AssetCode {
+    let imagePath = options.imagePath ?? '/asset/.';
+
+    // ensure imagePath ends with /. to copy the **content** at this path
+    if (imagePath.endsWith('/')) {
+      imagePath = `${imagePath}.`;
+    } else if (!imagePath.endsWith('/.')) {
+      imagePath = `${imagePath}/.`;
+    }
+
     const assetPath = cdk.DockerImage
       .fromBuild(path, options)
-      .cp(options.imagePath ?? '/asset', options.outputPath);
+      .cp(imagePath, options.outputPath);
+
     return new AssetCode(assetPath);
   }
 

packages/@aws-cdk/aws-lambda/test/code.test.ts

@@ -331,6 +331,23 @@ describe('code', () => {
   });
 
   describe('lambda.Code.fromDockerBuild', () => {
+    let fromBuildMock: jest.SpyInstance<cdk.DockerImage>;
+    let cpMock: jest.Mock<any, any>;
+
+    beforeEach(() => {
+      cpMock = jest.fn().mockReturnValue(path.join(__dirname, 'docker-build-lambda'));
+      fromBuildMock = jest.spyOn(cdk.DockerImage, 'fromBuild').mockImplementation(() => ({
+        cp: cpMock,
+        image: 'tag',
+        run: jest.fn(),
+        toJSON: jest.fn(),
+      }));
+    });
+
+    afterEach(() => {
+      fromBuildMock.mockRestore();
+    });
+
     test('can use the result of a Docker build as an asset', () => {
       // given
       const stack = new cdk.Stack();
@@ -346,10 +363,47 @@ describe('code', () => {
       // then
       expect(stack).toHaveResource('AWS::Lambda::Function', {
         Metadata: {
-          [cxapi.ASSET_RESOURCE_METADATA_PATH_KEY]: 'asset.38cd320fa97b348accac88e48d9cede4923f7cab270ce794c95a665be83681a8',
+          [cxapi.ASSET_RESOURCE_METADATA_PATH_KEY]: 'asset.fbafdbb9ae8d1bae0def415b791a93c486d18ebc63270c748abecc3ac0ab9533',
           [cxapi.ASSET_RESOURCE_METADATA_PROPERTY_KEY]: 'Code',
         },
       }, ResourcePart.CompleteDefinition);
+
+      expect(fromBuildMock).toHaveBeenCalledWith(path.join(__dirname, 'docker-build-lambda'), {});
+      expect(cpMock).toHaveBeenCalledWith('/asset/.', undefined);
+    });
+
+    test('fromDockerBuild appends /. to an image path not ending with a /', () => {
+      // given
+      const stack = new cdk.Stack();
+
+      // when
+      new lambda.Function(stack, 'Fn', {
+        code: lambda.Code.fromDockerBuild(path.join(__dirname, 'docker-build-lambda'), {
+          imagePath: '/my/image/path',
+        }),
+        handler: 'index.handler',
+        runtime: lambda.Runtime.NODEJS_12_X,
+      });
+
+      // then
+      expect(cpMock).toHaveBeenCalledWith('/my/image/path/.', undefined);
+    });
+
+    test('fromDockerBuild appends . to an image path ending with a /', () => {
+      // given
+      const stack = new cdk.Stack();
+
+      // when
+      new lambda.Function(stack, 'Fn', {
+        code: lambda.Code.fromDockerBuild(path.join(__dirname, 'docker-build-lambda'), {
+          imagePath: '/my/image/path/',
+        }),
+        handler: 'index.handler',
+        runtime: lambda.Runtime.NODEJS_12_X,
+      });
+
+      // then
+      expect(cpMock).toHaveBeenCalledWith('/my/image/path/.', undefined);
     });
   });
 });

packages/@aws-cdk/aws-lambda/test/docker-build-lambda/Dockerfile

@@ -1,3 +1,3 @@
 FROM public.ecr.aws/amazonlinux/amazonlinux:latest
 
-COPY index.js /asset
+COPY index.js /asset/