feat(aws-lambda-python): add command hooks for bundling to allow for execution of custom commands in the build container

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

@@ -198,3 +198,39 @@ new python.PythonFunction(this, 'function', {
   },
 });
 ```
+
+## Command hooks
+
+It is  possible to run additional commands by specifying the `commandHooks` prop:
+
+```ts
+const entry = '/path/to/function';
+new python.PythonFunction(this, 'function', {
+  entry,
+  runtime: Runtime.PYTHON_3_8,
+  bundling: {
+    commandHooks: {
+      // run tests
+      beforeBundling(inputDir: string): string[] {
+        return ['pytest'];
+      },
+      afterBundling(inputDir: string): string[] {
+        return ['pylint'];
+      },
+      // ...
+    },
+  },
+});
+```
+
+The following hooks are available:
+
+- `beforeBundling`: runs before all bundling commands
+- `afterBundling`: runs after all bundling commands
+
+They all receive the directory containing the dependencies file (`inputDir`) and the
+directory where the bundled asset will be output (`outputDir`). They must return
+an array of commands to run. Commands are chained with `&&`.
+
+The commands will run in the environment in which bundling occurs: inside the
+container for Docker bundling or on the host OS for local bundling.

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

@@ -2,7 +2,7 @@ import * as path from 'path';
 import { Architecture, AssetCode, Code, Runtime } from '@aws-cdk/aws-lambda';
 import { AssetStaging, BundlingOptions as CdkBundlingOptions, DockerImage } from '@aws-cdk/core';
 import { Packaging, DependenciesFile } from './packaging';
-import { BundlingOptions } from './types';
+import { BundlingOptions, ICommandHooks } from './types';
 
 /**
  * Dependency files to exclude from the asset hash.
@@ -68,6 +68,7 @@ export class Bundling implements CdkBundlingOptions {
       outputPathSuffix = '',
       image,
       poetryIncludeHashes,
+      commandHooks,
     } = props;
 
     const outputPath = path.posix.join(AssetStaging.BUNDLING_OUTPUT_DIR, outputPathSuffix);
@@ -77,6 +78,7 @@ export class Bundling implements CdkBundlingOptions {
       inputDir: AssetStaging.BUNDLING_INPUT_DIR,
       outputDir: outputPath,
       poetryIncludeHashes,
+      commandHooks,
     });
 
     this.image = image ?? DockerImage.fromBuild(path.join(__dirname, '../lib'), {
@@ -93,12 +95,14 @@ export class Bundling implements CdkBundlingOptions {
   private createBundlingCommand(options: BundlingCommandOptions): string[] {
     const packaging = Packaging.fromEntry(options.entry, options.poetryIncludeHashes);
     let bundlingCommands: string[] = [];
+    bundlingCommands.push(...options.commandHooks?.beforeBundling(options.inputDir, options.outputDir) ?? []);
     bundlingCommands.push(`cp -rTL ${options.inputDir}/ ${options.outputDir}`);
     bundlingCommands.push(`cd ${options.outputDir}`);
     bundlingCommands.push(packaging.exportCommand ?? '');
     if (packaging.dependenciesFile) {
       bundlingCommands.push(`python -m pip install -r ${DependenciesFile.PIP} -t ${options.outputDir}`);
     }
+    bundlingCommands.push(...options.commandHooks?.afterBundling(options.inputDir, options.outputDir) ?? []);
     return bundlingCommands;
   }
 }
@@ -108,6 +112,7 @@ interface BundlingCommandOptions {
   readonly inputDir: string;
   readonly outputDir: string;
   readonly poetryIncludeHashes?: boolean;
+  readonly commandHooks?: ICommandHooks
 }
 
 /**

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

@@ -86,4 +86,45 @@ export interface BundlingOptions {
    * @default - Based on `assetHashType`
    */
   readonly assetHash?: string;
+
+  /**
+   * Command hooks
+   *
+   * @default - do not run additional commands
+   */
+  readonly commandHooks?: ICommandHooks;
+}
+
+/**
+ * Command hooks
+ *
+ * These commands will run in the environment in which bundling occurs: inside
+ * the container for Docker bundling or on the host OS for local bundling.
+ *
+ * Commands are chained with `&&`.
+ *
+ * ```text
+ * {
+ *   // Run tests prior to bundling
+ *   beforeBundling(inputDir: string, outputDir: string): string[] {
+ *     return [`pytest`];
+ *   }
+ *   // ...
+ * }
+ * ```
+ */
+export interface ICommandHooks {
+  /**
+   * Returns commands to run before bundling.
+   *
+   * Commands are chained with `&&`.
+   */
+  beforeBundling(inputDir: string, outputDir: string): string[];
+
+  /**
+   * Returns commands to run after bundling.
+   *
+   * Commands are chained with `&&`.
+   */
+  afterBundling(inputDir: string, outputDir: string): string[];
 }

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

@@ -299,3 +299,32 @@ test('Build docker image when bundling is not skipped', () => {
 
   expect(DockerImage.fromBuild).toHaveBeenCalled();
 });
+
+test('with command hooks', () => {
+  const entry = path.join(__dirname, 'lambda-handler');
+  Bundling.bundle({
+    entry: entry,
+    runtime: Runtime.PYTHON_3_7,
+    skip: false,
+    commandHooks: {
+      beforeBundling(inputDir: string, outputDir: string): string[] {
+        return [
+          `echo hello > ${inputDir}/a.txt`,
+          `cp ${inputDir}/a.txt ${outputDir}`,
+        ];
+      },
+      afterBundling(inputDir: string, outputDir: string): string[] {
+        return [`cp ${inputDir}/b.txt ${outputDir}/txt`];
+      },
+    },
+  });
+
+  expect(Code.fromAsset).toHaveBeenCalledWith(entry, expect.objectContaining({
+    bundling: expect.objectContaining({
+      command: [
+        'bash', '-c',
+        expect.stringMatching(/^echo hello > \/asset-input\/a.txt && cp \/asset-input\/a.txt \/asset-output && .+ && cp \/asset-input\/b.txt \/asset-output\/txt$/),
+      ],
+    }),
+  }));
+});