fix: skip validation for server decompressed objects (#1063)

* fix: skip validation for server decompressed objects

* fix: formatting changes to todo comment for tracking

* fix: lint

* fix: remove unnecessary var set

* use async/await

* listen to response evt on read stream

* npm run fix

Co-authored-by: Christopher Wilcox <crwilcox@google.com>

src/file.ts

@@ -1212,6 +1212,7 @@ class File extends ServiceObject<File> {
     // once Node 8 support is discontinued
     const throughStream = streamEvents(through()) as Duplex;
 
+    let isServedCompressed = true;
     let crc32c = true;
     let md5 = false;
 
@@ -1294,7 +1295,7 @@ class File extends ServiceObject<File> {
       //      applicable, to the user.
       const onResponse = (
         err: Error | null,
-        body: ResponseBody,
+        _body: ResponseBody,
         rawResponseStream: Metadata
       ) => {
         if (err) {
@@ -1312,7 +1313,7 @@ class File extends ServiceObject<File> {
         rawResponseStream.on('error', onComplete);
 
         const headers = rawResponseStream.toJSON().headers;
-        const isCompressed = headers['content-encoding'] === 'gzip';
+        isServedCompressed = headers['content-encoding'] === 'gzip';
         const shouldRunValidation = !rangeRequest && (crc32c || md5);
         const throughStreams: Writable[] = [];
 
@@ -1321,7 +1322,7 @@ class File extends ServiceObject<File> {
           throughStreams.push(validateStream);
         }
 
-        if (isCompressed && options.decompress) {
+        if (isServedCompressed && options.decompress) {
           throughStreams.push(zlib.createGunzip());
         }
 
@@ -1369,6 +1370,16 @@ class File extends ServiceObject<File> {
 
         onCompleteCalled = true;
 
+        // TODO(https://github.com/googleapis/nodejs-storage/issues/709):
+        // Remove once the backend issue is fixed.
+        // If object is stored compressed (having metadata.contentEncoding === 'gzip')
+        // and was served decompressed, then skip checksum validation because the
+        // remote checksum is computed against the compressed version of the object.
+        if (this.metadata.contentEncoding === 'gzip' && !isServedCompressed) {
+          throughStream.end();
+          return;
+        }
+
         const hashes = {
           crc32c: this.metadata.crc32c,
           md5: this.metadata.md5Hash,
@@ -1602,6 +1613,8 @@ class File extends ServiceObject<File> {
    *     supported for composite objects. An error will be raised if MD5 is
    *     specified but is not available. You may also choose to skip validation
    *     completely, however this is **not recommended**.
+   *     NOTE: Validation is automatically skipped for objects that were
+   *     uploaded using the `gzip` option and have already compressed content.
    */
   /**
    * Create a writable stream to overwrite the contents of the file in your

system-test/storage.ts

@@ -2250,6 +2250,33 @@ describe('storage', () => {
       });
     });
 
+    it('should skip validation if file is served decompressed', async () => {
+      const filename = 'logo-gzipped.png';
+      await bucket.upload(FILES.logo.path, {destination: filename, gzip: true});
+
+      tmp.setGracefulCleanup();
+      const {name: tmpFilePath} = tmp.fileSync();
+
+      const file = bucket.file(filename);
+
+      await new Promise((resolve, reject) => {
+        file
+          .createReadStream()
+          .on('error', reject)
+          .on('response', raw => {
+            assert.strictEqual(
+              raw.toJSON().headers['content-encoding'],
+              undefined
+            );
+          })
+          .pipe(fs.createWriteStream(tmpFilePath))
+          .on('error', reject)
+          .on('finish', resolve);
+      });
+
+      await file.delete();
+    });
+
     describe('simple write', () => {
       it('should save arbitrary data', done => {
         const file = bucket.file('TestFile');

test/file.ts

@@ -1293,7 +1293,7 @@ describe('File', () => {
 
     describe('validation', () => {
       const data = 'test';
-      let fakeValidationStream: stream.Stream;
+      let fakeValidationStream: stream.Stream & {test: Function};
 
       beforeEach(() => {
         file.metadata.mediaLink = 'http://uri';
@@ -1306,16 +1306,60 @@ describe('File', () => {
           callback();
         };
 
-        fakeValidationStream = through();
-        // tslint:disable-next-line no-any
-        (fakeValidationStream as any).test = () => {
-          return true;
-        };
+        fakeValidationStream = Object.assign(through(), {test: () => true});
         hashStreamValidationOverride = () => {
           return fakeValidationStream;
         };
       });
 
+      describe('server decompression', () => {
+        beforeEach(() => {
+          handleRespOverride = (
+            err: Error,
+            res: {},
+            body: {},
+            callback: Function