feat(lambda-python): add support for buildArgs

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

@@ -36,6 +36,16 @@ new PythonFunction(this, 'MyFunction', {
 });
 ```
 
+Additional `buildArgs` to use when bundling the Docker building image can be provided as:
+
+```ts
+new PythonFunction(this, 'my-handler', {
+  buildArgs: {
+    HTTPS_PROXY: 'https://127.0.0.1:3001',
+  },
+});
+```
+
 All other properties of `lambda.Function` are supported, see also the [AWS Lambda construct library](https://github.com/aws/aws-cdk/tree/master/packages/%40aws-cdk/aws-lambda).
 
 ## Module Dependencies
@@ -44,9 +54,9 @@ If `requirements.txt` or `Pipfile` exists at the entry path, the construct will
 all required modules in a [Lambda compatible Docker container](https://gallery.ecr.aws/sam/build-python3.7)
 according to the `runtime`.
 
-Python bundles are only recreated and published when a file in a source directory has changed. 
+Python bundles are only recreated and published when a file in a source directory has changed.
 Therefore (and as a general best-practice), it is highly recommended to commit a lockfile with a
-list of all transitive dependencies and their exact versions. 
+list of all transitive dependencies and their exact versions.
 This will ensure that when any dependency version is updated, the bundle asset is recreated and uploaded.
 
 To that end, we recommend using [`pipenv`] or [`poetry`] which has lockfile support.

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

@@ -71,13 +71,20 @@ export interface BundlingOptions {
    * @default - based on `assetHashType`
    */
   readonly assetHash?: string;
+
+  /**
+   * Build arguments to pass when building the bundling image.
+   *
+   * @default - no build arguments are passed
+   */
+  readonly buildArgs?: { [key: string]: string };
 }
 
 /**
  * Produce bundled Lambda asset code
  */
 export function bundle(options: BundlingOptions): lambda.Code {
-  const { entry, runtime, outputPathSuffix } = options;
+  const { entry, runtime, outputPathSuffix, buildArgs } = options;
 
   const stagedir = cdk.FileSystem.mkdtemp('python-bundling-');
   const hasDeps = stageDependencies(entry, stagedir);
@@ -100,6 +107,7 @@ export function bundle(options: BundlingOptions): lambda.Code {
 
   const image = cdk.DockerImage.fromBuild(stagedir, {
     buildArgs: {
+      ...buildArgs,
       IMAGE: runtime.bundlingDockerImage.image,
     },
     file: dockerfile,

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

@@ -77,6 +77,13 @@ export interface PythonFunctionProps extends lambda.FunctionOptions {
    * @default - based on `assetHashType`
    */
   readonly assetHash?: string;
+
+  /**
+   * Build arguments to pass when building the bundling image.
+   *
+   * @default - no build arguments are passed
+   */
+  readonly buildArgs?: { [key: string]: string };
 }
 
 /**
@@ -112,6 +119,7 @@ export class PythonFunction extends lambda.Function {
         outputPathSuffix: '.',
         assetHashType: props.assetHashType,
         assetHash: props.assetHash,
+        buildArgs: props.buildArgs,
       }),
       handler: `${index.slice(0, -3)}.${handler}`,
     });

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

@@ -21,6 +21,13 @@ export interface PythonLayerVersionProps extends lambda.LayerVersionOptions {
    * @default - All runtimes are supported.
    */
   readonly compatibleRuntimes?: lambda.Runtime[];
+
+  /**
+   * Build arguments to pass when building the bundling image.
+   *
+   * @default - no build arguments are passed
+   */
+  readonly buildArgs?: { [key: string]: string };
 }
 
 /**
@@ -50,6 +57,7 @@ export class PythonLayerVersion extends lambda.LayerVersion {
         entry,
         runtime,
         outputPathSuffix: 'python',
+        buildArgs: props.buildArgs,
       }),
     });
   }

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

@@ -1,11 +1,10 @@
 import * as fs from 'fs';
 import * as path from 'path';
 import { Code, Runtime } from '@aws-cdk/aws-lambda';
-import { FileSystem } from '@aws-cdk/core';
+import { DockerImage, FileSystem } from '@aws-cdk/core';
 import { stageDependencies, bundle } from '../lib/bundling';
 
 jest.mock('@aws-cdk/aws-lambda');
-
 jest.mock('child_process', () => ({
   spawnSync: jest.fn(() => {
     return {
@@ -19,8 +18,17 @@ jest.mock('child_process', () => ({
   }),
 }));
 
+// Mock DockerImage.fromAsset() to avoid building the image
+let fromBuildMock: jest.SpyInstance<DockerImage>;
 beforeEach(() => {
   jest.clearAllMocks();
+
+  fromBuildMock = jest.spyOn(DockerImage, 'fromBuild').mockReturnValue({
+    image: 'built-image',
+    cp: () => 'dest-path',
+    run: () => {},
+    toJSON: () => 'built-image',
+  });
 });
 
 test('Bundling a function without dependencies', () => {
@@ -139,3 +147,22 @@ describe('Dependency detection', () => {
     expect(stageDependencies(sourcedir, '/dummy')).toEqual(false);
   });
 });
+
+test('Bundling Docker with build args', () => {
+  const entry = path.join(__dirname, 'lambda-handler-nodeps');
+  bundle({
+    entry,
+    runtime: Runtime.PYTHON_3_7,
+    outputPathSuffix: '.',
+    buildArgs: {
+      HELLO: 'WORLD',
+    },
+  });
+
+  expect(fromBuildMock).toHaveBeenCalledWith(expect.stringContaining('/tmp/python-bundling'),
+    expect.objectContaining({
+      buildArgs: expect.objectContaining({
+        HELLO: 'WORLD',
+      }),
+    }));
+});