fix(aws-ecr-assets): TarballImageAsset respects CDK_DOCKER environment variable

Author: pahud

packages/aws-cdk-lib/aws-ecr-assets/README.md

@@ -163,6 +163,10 @@ This will instruct the toolkit to add the tarball as a file asset. During deploy
 from `local-image.tar`, push it to an Amazon ECR repository and wire the name of the repository as CloudFormation parameters
 to your stack.
 
+Similar to `DockerImageAsset`, you can set the `CDK_DOCKER` environment variable to provide a custom Docker executable 
+command or path. This may be needed when building in environments where the standard docker cannot be executed or when 
+using alternative container runtimes like Finch.
+
 ## Publishing images to ECR repositories
 
 `DockerImageAsset` is designed for seamless build & consumption of image assets by CDK code deployed to multiple environments

packages/aws-cdk-lib/aws-ecr-assets/lib/tarball-asset.ts

@@ -107,7 +107,7 @@ export class TarballImageAsset extends Construct implements IAsset {
       executable: [
         'sh',
         '-c',
-        `docker load -i ${relativePathInOutDir} | tail -n 1 | sed "${DOCKER_LOAD_OUTPUT_REGEX}"`,
+        `${process.env.CDK_DOCKER ?? 'docker'} load -i ${relativePathInOutDir} | tail -n 1 | sed "${DOCKER_LOAD_OUTPUT_REGEX}"`,
       ],
       displayName: props.displayName ?? Names.stackRelativeConstructPath(this),
     });

packages/aws-cdk-lib/aws-ecr-assets/test/tarball-asset.test.ts

@@ -190,6 +190,40 @@ describe('image asset', () => {
     expect(oldSedWithNewFormat.stdout.toString().trim()).not.toBe('sha256:4a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a');
     expect(oldSedWithNewFormat.stdout.toString().trim()).toBe('Loaded image ID: sha256:4a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a');
   });
+
+  test('respects CDK_DOCKER environment variable', () => {
+    // GIVEN
+    const originalCdkDocker = process.env.CDK_DOCKER;
+    process.env.CDK_DOCKER = 'custom-docker';
+
+    try {
+      const app = new App();
+      const stack = new Stack(app);
+      const asset = new TarballImageAsset(stack, 'Image', {
+        tarballFile,
+      });
+
+      // WHEN
+      const asm = app.synth();
+
+      // THEN
+      const manifestArtifact = getAssetManifest(asm);
+      const manifest = readAssetManifest(manifestArtifact);
+
+      expect(manifest.dockerImages?.[asset.assetHash]?.source?.executable).toEqual([
+        'sh',
+        '-c',
+        `custom-docker load -i asset.${asset.assetHash}.tar | tail -n 1 | sed "${DOCKER_LOAD_OUTPUT_REGEX}"`,
+      ]);
+    } finally {
+      // Cleanup
+      if (originalCdkDocker !== undefined) {
+        process.env.CDK_DOCKER = originalCdkDocker;
+      } else {
+        delete process.env.CDK_DOCKER;
+      }
+    }
+  });
 });
 
 function isAssetManifest(x: cxapi.CloudArtifact): x is cxapi.AssetManifestArtifact {