feat(lambda-nodejs): command hooks

packages/@aws-cdk/aws-lambda-nodejs/README.md

@@ -144,3 +144,26 @@ $ yarn add --dev esbuild@0
 To force bundling in a Docker container, set the `forceDockerBundling` prop to `true`. This
 is useful if your function relies on node modules that should be installed (`nodeModules` prop, see [above](#install-modules)) in a Lambda compatible environment. This is usually the
 case with modules using native dependencies.
+
+### Command hooks
+It is possible to run additional commands by specifying the `commandHooks` prop:
+
+```ts
+new lambda.NodejsFunction(this, 'my-handler-with-commands', {
+  commandHooks: {
+    // Copy a file so that it will be included in the bundled asset
+    afterBundling(inputDir: string, outputDir: string): string {
+      return `cp ${inputDir}/important-file.node ${outputDir}`
+    }
+  }
+});
+```
+
+The following hooks are available:
+- `beforeBundling`: runs before all bundling commands
+- `afterInstall`: runs before node modules installation
+- `afterBundling`: runs after all bundling commands
+
+They all receive the directory containing the lock file (`inputDir`) and the
+directory where the bundled asset will be output (`outputDir`). They must return
+the command to run as a `string`.

packages/@aws-cdk/aws-lambda-nodejs/lib/bundling.ts

@@ -169,7 +169,13 @@ export class Bundling implements cdk.BundlingOptions {
       ]);
     }
 
-    return chain([esbuildCommand, depsCommand]);
+    return chain([
+      this.props.commandHooks?.beforeBundling?.(inputDir, outputDir) ?? '',
+      esbuildCommand,
+      (this.props.nodeModules && this.props.commandHooks?.beforeInstall?.(inputDir, outputDir)) ?? '',
+      depsCommand,
+      this.props.commandHooks?.afterBundling?.(inputDir, outputDir) ?? '',
+    ]);
   }
 }
 

packages/@aws-cdk/aws-lambda-nodejs/lib/types.ts

@@ -101,4 +101,33 @@ export interface BundlingOptions {
    * @default - use the Docker image provided by @aws-cdk/aws-lambda-nodejs
    */
   readonly bundlingDockerImage?: BundlingDockerImage;
+
+  /**
+   * Command hooks
+   *
+   * @default - do not run additional commands
+   */
+  readonly commandHooks?: ICommandHooks;
+}
+
+/**
+ * Command hooks
+ */
+export interface ICommandHooks {
+  /**
+   * Returns a command to run before bundling
+   */
+  beforeBundling?(inputDir: string, outputDir: string): string;
+
+  /**
+   * Returns a command to run before installing node modules.
+   *
+   * This hook only runs when node modules are installed
+   */
+  beforeInstall?(inputDir: string, outputDir: string): string;
+
+  /**
+   * Returns a command to run after bundling
+   */
+  afterBundling?(inputDir: string, outputDir: string): string;
 }

packages/@aws-cdk/aws-lambda-nodejs/test/bundling.test.ts

@@ -255,3 +255,30 @@ test('Custom bundling docker image', () => {
     }),
   });
 });
+
+test('with command hooks', () => {
+  Bundling.bundle({
+    entry,
+    depsLockFilePath,
+    runtime: Runtime.NODEJS_12_X,
+    commandHooks: {
+      beforeBundling(inputDir: string, outputDir: string): string {
+        return `cp ${inputDir}/a.txt ${outputDir}`;
+      },
+      afterBundling(inputDir: string, outputDir: string): string {
+        return `cp ${inputDir}/b.txt ${outputDir}/txt`;
+      },
+    },
+    forceDockerBundling: true,
+  });
+
+  expect(Code.fromAsset).toHaveBeenCalledWith(path.dirname(depsLockFilePath), {
+    assetHashType: AssetHashType.OUTPUT,
+    bundling: expect.objectContaining({
+      command: [
+        'bash', '-c',
+        expect.stringMatching(/^cp \/asset-input\/a.txt \/asset-output && .+ && cp \/asset-input\/b.txt \/asset-output\/txt$/),
+      ],
+    }),
+  });
+});