fix(core): BundlingDockerImage.fromAsset() does not return a Bundling…

…DockerImage (#13846)

A previous change missed to fix the 'return' statement on this method.

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*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*

packages/@aws-cdk/core/lib/bundling.ts

@@ -157,8 +157,8 @@ export class BundlingDockerImage {
    *
    * @deprecated use DockerImage.fromBuild()
    */
-  public static fromAsset(path: string, options: DockerBuildOptions = {}) {
-    DockerImage.fromBuild(path, options) as BundlingDockerImage;
+  public static fromAsset(path: string, options: DockerBuildOptions = {}): BundlingDockerImage {
+    return DockerImage.fromBuild(path, options);
   }
 
   /** @param image The Docker image */

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

@@ -173,6 +173,25 @@ nodeunitShim({
     test.done();
   },
 
+  'fromAsset'(test: Test) {
+    sinon.stub(child_process, 'spawnSync').returns({
+      status: 0,
+      stderr: Buffer.from('stderr'),
+      stdout: Buffer.from('sha256:1234567890abcdef'),
+      pid: 123,
+      output: ['stdout', 'stderr'],
+      signal: null,
+    });
+
+    const imagePath = path.join(__dirname, 'fs/fixtures/test1');
+    const image = BundlingDockerImage.fromAsset(imagePath, {
+      file: 'my-dockerfile',
+    });
+    test.ok(image);
+    test.ok(image.image);
+    test.done();
+  },
+
   'custom entrypoint is passed through to docker exec'(test: Test) {
     const spawnSyncStub = sinon.stub(child_process, 'spawnSync').returns({
       status: 0,