feat(lambda-python): support build args (#12949)

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

@@ -33,6 +33,9 @@ new PythonFunction(this, 'MyFunction', {
   index: 'my_index.py', // optional, defaults to 'index.py'
   handler: 'my_exported_func', // optional, defaults to 'handler'
   runtime: lambda.Runtime.PYTHON_3_6, // optional, defaults to lambda.Runtime.PYTHON_3_7
+  build_args: {
+    HTTPS_PROXY: 'https://127.0.0.1:3001',
+  }, // optional, defaults to {}
 });
 ```
 
@@ -86,3 +89,15 @@ new lambda.PythonFunction(this, 'MyFunction', {
   ],
 });
 ```
+
+**Lambda with custom Docker Build Time Variables**
+
+Use the `buildArgs` parameter to pass build arguments when building the bundling image:
+
+```ts
+new lambda.PythonFunction(this, 'MyFunction', {
+  buildArgs: {
+    HTTPS_PROXY: 'https://127.0.0.1:3001',
+  },
+});
+```

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

@@ -71,6 +71,13 @@ 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 };
 }
 
 /**
@@ -100,6 +107,7 @@ export function bundle(options: BundlingOptions): lambda.Code {
 
   const image = cdk.DockerImage.fromBuild(stagedir, {
     buildArgs: {
+      ...options.buildArgs ?? {},
       IMAGE: runtime.bundlingDockerImage.image,
     },
     file: dockerfile,

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

@@ -77,6 +77,14 @@ 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 +120,7 @@ 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 +21,14 @@ 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 };
+
 }
 
 /**
@@ -51,6 +59,7 @@ export class PythonLayerVersion extends lambda.LayerVersion {
         entry,
         runtime,
         outputPathSuffix: 'python',
+        buildArgs: props.buildArgs,
       }),
     });
   }

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

@@ -1,7 +1,7 @@
 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 { FileSystem, DockerImage } from '@aws-cdk/core';
 import { stageDependencies, bundle } from '../lib/bundling';
 
 jest.mock('@aws-cdk/aws-lambda');
@@ -139,3 +139,23 @@ describe('Dependency detection', () => {
     expect(stageDependencies(sourcedir, '/dummy')).toEqual(false);
   });
 });
+
+let fromAssetMock = jest.spyOn(DockerImage, 'fromBuild');
+test('with Docker build args', () => {
+  const entry = path.join(__dirname, 'lambda-handler');
+
+  bundle({
+    entry,
+    runtime: Runtime.PYTHON_3_7,
+    buildArgs: {
+      HELLO: 'WORLD',
+    },
+    outputPathSuffix: 'python',
+  });
+
+  expect(fromAssetMock).toHaveBeenCalledWith(expect.stringMatching(/python-bundling-/), expect.objectContaining({
+    buildArgs: expect.objectContaining({
+      HELLO: 'WORLD',
+    }),
+  }));
+});