feat(aws-cdk): directory assets follow symlinks (#1318)

When building a nodejs lambda it is really common for dependencies under the `node_modules` folder to actually be symlink'd to other folders on your system. The symlinks will now be followed and the indicated files packaged (instead of the symlinks themselves).

Fixes #731

packages/aws-cdk/lib/archive.ts

@@ -6,7 +6,16 @@ export function zipDirectory(directory: string, outputFile: string): Promise<voi
   return new Promise((ok, fail) => {
     const output = fs.createWriteStream(outputFile);
     const archive = archiver('zip');
-    archive.directory(directory, false);
+    // The below options are needed to support following symlinks when building zip files:
+    // -  nodir: This will prevent symlinks themselves from being copied into the zip.
+    // - follow: This will follow symlinks and copy the files within.
+    const globOptions = {
+      dot: true,
+      nodir: true,
+      follow: true,
+      cwd: directory
+    };
+    archive.glob('**', globOptions);
     archive.pipe(output);
     archive.finalize();
 

packages/aws-cdk/test/test-archive-follow/data/linked

@@ -0,0 +1 @@
+../linked

packages/aws-cdk/test/test-archive-follow/data/one.txt

@@ -0,0 +1 @@
+1

packages/aws-cdk/test/test-archive-follow/linked/two.txt

@@ -0,0 +1 @@
+2

packages/aws-cdk/test/test.archive.ts

@@ -43,5 +43,24 @@ export = {
 
     test.deepEqual(hash1, hash2, 'md5 hash of two zips of the same content are not the same');
     test.done();
+  },
+
+  async 'zipDirectory follows symlinks'(test: Test) {
+    const originalDir = path.join(__dirname, 'test-archive-follow', 'data');
+    const stagingDir = await fs.mkdtemp(path.join(os.tmpdir(), 'test.archive'));
+    const zipFile = path.join(stagingDir, 'output.zip');
+    const extractDir = await fs.mkdtemp(path.join(os.tmpdir(), 'test.archive.follow'));
+
+    try {
+      await zipDirectory(originalDir, zipFile);
+      await exec(`unzip ${zipFile}`, { cwd: extractDir });
+      await exec(`diff -bur ${originalDir} ${extractDir}`);
+    } catch (e) {
+      test.ok(false, `extracted directory ${extractDir} differs from original ${originalDir}, symlinks not followed.`);
+    }
+
+    await fs.remove(stagingDir);
+    await fs.remove(extractDir);
+    test.done();
   }
 };