feat(assets): isZipArchive indicates if this is a zip asset (#944)

Adds a property to `Asset` called `isZipArchive` which allows
checking if the assets represents a zip file. This will be true
both for `FileAsset` that references an actual .zip file and
for `ZipDirectoryAsset`.

packages/@aws-cdk/assets/lib/asset.ts

@@ -65,7 +65,16 @@ export class Asset extends cdk.Construct {
    */
   public readonly assetPath: string;
 
-  private readonly bucket: s3.BucketRef;
+  /**
+   * The S3 bucket in which this asset resides.
+   */
+  public readonly bucket: s3.BucketRef;
+
+  /**
+   * Indicates if this asset is a zip archive. Allows constructs to ensure that the
+   * correct file type was used.
+   */
+  public readonly isZipArchive: boolean;
 
   /**
    * The S3 prefix where all different versions of this asset are stored
@@ -78,6 +87,11 @@ export class Asset extends cdk.Construct {
     // resolve full path
     this.assetPath = path.resolve(props.path);
 
+    // sets isZipArchive based on the type of packaging and file extension
+    this.isZipArchive = props.packaging === AssetPackaging.ZipDirectory
+      ? true
+      : this.assetPath.toLowerCase().endsWith('.zip');
+
     validateAssetOnDisk(this.assetPath, props.packaging);
 
     // add parameters for s3 bucket and s3 key. those will be set by

packages/@aws-cdk/assets/test/test.asset.ts

@@ -112,4 +112,28 @@ export = {
 
     test.done();
   },
+
+  'isZipArchive indicates if the asset represents a .zip file (either explicitly or via ZipDirectory packaging)'(test: Test) {
+    // GIVEN
+    const stack = new cdk.Stack();
+
+    // WHEN
+    const nonZipAsset = new FileAsset(stack, 'NonZipAsset', {
+      path: path.join(__dirname, 'sample-asset-directory', 'sample-asset-file.txt')
+    });
+
+    const zipDirectoryAsset = new ZipDirectoryAsset(stack, 'ZipDirectoryAsset', {
+      path: path.join(__dirname, 'sample-asset-directory')
+    });
+
+    const zipFileAsset = new FileAsset(stack, 'ZipFileAsset', {
+      path: path.join(__dirname, 'sample-asset-directory', 'sample-zip-asset.zip')
+    });
+
+    // THEN
+    test.equal(nonZipAsset.isZipArchive, false);
+    test.equal(zipDirectoryAsset.isZipArchive, true);
+    test.equal(zipFileAsset.isZipArchive, true);
+    test.done();
+  }
 };