chore(core): allow the bundler to re-use pre-existing bundler output

packages/@aws-cdk/core/lib/asset-staging.ts

@@ -89,10 +89,15 @@ export class AssetStaging extends Construct {
     this.fingerprintOptions = props;
 
     if (props.bundling) {
-      this.bundleDir = this.bundle(props.bundling);
-    }
+      const assetHashIfKnownInAdvance = props.assetHashType !== AssetHashType.BUNDLE
+        ? this.calculateHash(props)
+        : undefined;
 
-    this.assetHash = this.calculateHash(props);
+      this.bundleDir = this.bundle(props.bundling, assetHashIfKnownInAdvance);
+      this.assetHash = assetHashIfKnownInAdvance || this.calculateHash(props);
+    } else {
+      this.assetHash = this.calculateHash(props);
+    }
 
     const stagingDisabled = this.node.tryGetContext(cxapi.DISABLE_ASSET_STAGING_CONTEXT);
     if (stagingDisabled) {
@@ -137,15 +142,31 @@ export class AssetStaging extends Construct {
     }
   }
 
-  private bundle(options: BundlingOptions): string {
+  private bundle(options: BundlingOptions, assetHash?: string): string {
     // Temp staging directory in the working directory
     const stagingTmp = path.join('.', STAGING_TMP);
     fs.ensureDirSync(stagingTmp);
 
-    // Create temp directory for bundling inside the temp staging directory
-    const bundleDir = path.resolve(fs.mkdtempSync(path.join(stagingTmp, 'asset-bundle-')));
-    // Chmod the bundleDir to full access.
-    fs.chmodSync(bundleDir, 0o777);
+    let bundleDir = '';
+    if (assetHash !== undefined) {
+      // When an asset hash is known in advance of bundling, bundling is done into a dedicated staging directory.
+      bundleDir = path.resolve(path.join(stagingTmp, 'asset-bundle-hash-' + assetHash));
+
+      if (fs.existsSync(bundleDir)) {
+        // Pre-existing bundle directory. The bundle has already been generated once before, so lets provide it
+        // as-is to the caller.
+        return bundleDir;
+      }
+
+      fs.ensureDirSync(bundleDir);
+    } else {
+      // When the asset hash isn't known in advance, bundling is done into a temporary staging directory.
+
+      // Create temp directory for bundling inside the temp staging directory
+      bundleDir = path.resolve(fs.mkdtempSync(path.join(stagingTmp, 'asset-bundle-temp-')));
+      // Chmod the bundleDir to full access.
+      fs.chmodSync(bundleDir, 0o777);
+    }
 
     let user: string;
     if (options.user) {

packages/@aws-cdk/core/test/docker-stub.sh

@@ -6,6 +6,7 @@ set -euo pipefail
 # `/tmp/docker-stub.input` and accepts one of 3 commands that impact it's
 # behavior.
 
+echo "$@" >> /tmp/docker-stub.input.concat
 echo "$@" > /tmp/docker-stub.input
 
 if echo "$@" | grep "DOCKER_STUB_SUCCESS_NO_OUTPUT"; then

packages/@aws-cdk/core/test/test.staging.ts

@@ -7,6 +7,8 @@ import * as sinon from 'sinon';
 import { App, AssetHashType, AssetStaging, BundlingDockerImage, Stack } from '../lib';
 
 const STUB_INPUT_FILE = '/tmp/docker-stub.input';
+const STUB_INPUT_CONCAT_FILE = '/tmp/docker-stub.input.concat';
+const STAGING_TMP_DIRECTORY = path.join('.', '.cdk.staging');
 
 enum DockerStubCommand {
   SUCCESS           = 'DOCKER_STUB_SUCCESS',
@@ -26,6 +28,12 @@ export = {
     if (fs.existsSync(STUB_INPUT_FILE)) {
       fs.unlinkSync(STUB_INPUT_FILE);
     }
+    if (fs.existsSync(STUB_INPUT_CONCAT_FILE)) {
+      fs.unlinkSync(STUB_INPUT_CONCAT_FILE);
+    }
+    if (fs.existsSync(STAGING_TMP_DIRECTORY)) {
+      fs.removeSync(STAGING_TMP_DIRECTORY);
+    }
     cb();
     sinon.restore();
   },
@@ -106,8 +114,6 @@ export = {
     const stack = new Stack(app, 'stack');
     const directory = path.join(__dirname, 'fs', 'fixtures', 'test1');
     const ensureDirSyncSpy = sinon.spy(fs, 'ensureDirSync');
-    const mkdtempSyncSpy = sinon.spy(fs, 'mkdtempSync');
-    const chmodSyncSpy = sinon.spy(fs, 'chmodSync');
 
     // WHEN
     new AssetStaging(stack, 'Asset', {
@@ -133,10 +139,73 @@ export = {
     ]);
 
     // asset is bundled in a directory inside .cdk.staging
-    const stagingTmp = path.join('.', '.cdk.staging');
-    test.ok(ensureDirSyncSpy.calledWith(stagingTmp));
-    test.ok(mkdtempSyncSpy.calledWith(sinon.match(path.join(stagingTmp, 'asset-bundle-'))));
-    test.ok(chmodSyncSpy.calledWith(sinon.match(path.join(stagingTmp, 'asset-bundle-')), 0o777));
+    test.ok(ensureDirSyncSpy.calledWith(STAGING_TMP_DIRECTORY));
+    test.ok(ensureDirSyncSpy.calledWith(path.resolve(path.join(STAGING_TMP_DIRECTORY, 'asset-bundle-hash-2f37f937c51e2c191af66acf9b09f548926008ec68c575bd2ee54b6e997c0e00'))));
+
+    test.done();
+  },
+
+  'with bundling and non-bundle asset hash type'(test: Test) {
+    // GIVEN
+    const app = new App();
+    const stack = new Stack(app, 'stack');
+    const directory = path.join(__dirname, 'fs', 'fixtures', 'test1');
+    const ensureDirSyncSpy = sinon.spy(fs, 'ensureDirSync');
+
+    // WHEN
+    new AssetStaging(stack, 'Asset', {
+      sourcePath: directory,
+      bundling: {
+        image: BundlingDockerImage.fromRegistry('alpine'),
+        command: [ DockerStubCommand.SUCCESS ],
+      },
+    });
+
+    new AssetStaging(stack, 'AssetDuplicate', {
+      sourcePath: directory,
+      bundling: {
+        image: BundlingDockerImage.fromRegistry('alpine'),
+        command: [ DockerStubCommand.SUCCESS ],
+      },
+    });
+
+    // THEN
+    app.synth();
+
+    // We're testing that docker was run exactly once even though there are two bundling assets.
+    test.deepEqual(
+      readDockerStubInputConcat(),
+      `run --rm ${USER_ARG} -v /input:/asset-input:delegated -v /output:/asset-output:delegated -w /asset-input alpine DOCKER_STUB_SUCCESS`,
+    );
+
+    // asset is bundled in a directory inside .cdk.staging
+    test.ok(ensureDirSyncSpy.calledWith(STAGING_TMP_DIRECTORY));
+    test.ok(ensureDirSyncSpy.calledWith(path.resolve(path.join(STAGING_TMP_DIRECTORY, 'asset-bundle-hash-2f37f937c51e2c191af66acf9b09f548926008ec68c575bd2ee54b6e997c0e00'))));
+
+    test.done();
+  },
+
+  'with bundling and bundle asset hash type'(test: Test) {
+    // GIVEN
+    const app = new App();
+    const stack = new Stack(app, 'stack');
+    const directory = path.join(__dirname, 'fs', 'fixtures', 'test1');
+    const mkdtempSyncSpy = sinon.spy(fs, 'mkdtempSync');
+    const chmodSyncSpy = sinon.spy(fs, 'chmodSync');
+
+    // WHEN
+    new AssetStaging(stack, 'Asset', {
+      sourcePath: directory,
+      assetHashType: AssetHashType.BUNDLE,
+      bundling: {
+        image: BundlingDockerImage.fromRegistry('alpine'),
+        command: [ DockerStubCommand.SUCCESS ],
+      },
+    });
+
+    // THEN
+    test.ok(mkdtempSyncSpy.calledWith(sinon.match(path.join(STAGING_TMP_DIRECTORY, 'asset-bundle-temp-'))));
+    test.ok(chmodSyncSpy.calledWith(sinon.match(path.join(STAGING_TMP_DIRECTORY, 'asset-bundle-temp-')), 0o777));
 
     test.done();
   },
@@ -273,6 +342,7 @@ export = {
     // THEN
     test.throws(() => new AssetStaging(stack, 'Asset', {
       sourcePath: directory,
+      assetHashType: AssetHashType.BUNDLE,
       bundling: {
         image: BundlingDockerImage.fromRegistry('this-is-an-invalid-docker-image'),
         command: [ DockerStubCommand.FAIL ],
@@ -287,9 +357,20 @@ export = {
   },
 };
 
-function readDockerStubInput() {
-  const out = fs.readFileSync(STUB_INPUT_FILE, 'utf-8').trim();
-  return out
+// Reads a docker stub and cleans the volume paths out of the stub.
+function readAndCleanDockerStubInput(file: string) {
+  return fs
+    .readFileSync(file, 'utf-8')
+    .trim()
     .replace(/-v ([^:]+):\/asset-input/, '-v /input:/asset-input')
     .replace(/-v ([^:]+):\/asset-output/, '-v /output:/asset-output');
 }
+
+// Last docker input since last teardown
+function readDockerStubInput() {
+  return readAndCleanDockerStubInput(STUB_INPUT_FILE);
+}
+// Concatenated docker inputs since last teardown
+function readDockerStubInputConcat() {
+  return readAndCleanDockerStubInput(STUB_INPUT_CONCAT_FILE);
+}