fix: stop File.download from truncating output file on failure (#1720)

* fix: dont overwrite file * Notes * cleaned up tests * 🦉 Updates from OwlBot See https://github.com/googleapis/repo-automation-bots/blob/main/packages/owl-bot/README.md Co-authored-by: Daniel Bankhead <danielbankhead@google.com> Co-authored-by: Owl Bot <gcf-owl-bot[bot]@users.noreply.github.com>
googleapis · Nov 22, 2021 · d77979b · d77979b
1 parent 0c75e33
commit d77979b
Show file tree

Hide file tree

Showing 2 changed files with 61 additions and 5 deletions.
diff --git a/src/file.ts b/src/file.ts
@@ -2144,11 +2144,12 @@ class File extends ServiceObject<File> {
     const fileStream = this.createReadStream(options);
 
     if (destination) {
-      fileStream
-        .on('error', callback)
-        .pipe(fs.createWriteStream(destination))
-        .on('error', callback)
-        .on('finish', callback);
+      fileStream.on('error', callback).once('data', data => {
+        // We know that the file exists the server
+        const writable = fs.createWriteStream(destination);
+        writable.write(data);
+        fileStream.pipe(writable).on('error', callback).on('finish', callback);
+      });
     } else {
       getStream
         .buffer(fileStream)

diff --git a/test/file.ts b/test/file.ts
@@ -2697,6 +2697,61 @@ describe('File', () => {
         });
       });
 
+      it('should process the entire stream', done => {
+        tmp.setGracefulCleanup();
+        tmp.file(async (err, tmpFilePath) => {
+          assert.ifError(err);
+
+          const fileContents = 'abcdefghijklmnopqrstuvwxyz';
+
+          fileReadStream.on('resume', () => {
+            fileReadStream.emit('data', fileContents);
+            fileReadStream.emit('data', fileContents);
+            setImmediate(() => {
+              fileReadStream.emit('end');
+            });
+          });
+
+          file.download({destination: tmpFilePath}, (err: Error) => {
+            assert.ifError(err);
+            fs.readFile(tmpFilePath, (err, tmpFileContents) => {
+              assert.ifError(err);
+              assert.strictEqual(
+                fileContents + fileContents,
+                tmpFileContents.toString()
+              );
+              done();
+            });
+          });
+        });
+      });
+
+      it('file contents should remain unchanged if file nonexistent', done => {
+        tmp.setGracefulCleanup();
+        tmp.file(async (err, tmpFilePath) => {
+          assert.ifError(err);
+
+          const fileContents = 'file contents that should remain unchanged';
+          fs.writeFileSync(tmpFilePath, fileContents, 'utf-8');
+
+          const error = new Error('Error.');
+          fileReadStream.on('resume', () => {
+            setImmediate(() => {
+              fileReadStream.emit('error', error);
+            });
+          });
+
+          file.download({destination: tmpFilePath}, (err: Error) => {
+            assert.strictEqual(err, error);
+            fs.readFile(tmpFilePath, (err, tmpFileContents) => {
+              assert.ifError(err);
+              assert.strictEqual(fileContents, tmpFileContents.toString());
+              done();
+            });
+          });
+        });
+      });
+
       it('should execute callback with error', done => {
         tmp.setGracefulCleanup();
         tmp.file((err, tmpFilePath) => {