Fix worker-test and fs.createWriteStream spec incompliance

Summary:
The CircleCI build of metro is currently failing because `jest` fails to mock the `console` module. This is because the typeof console changed in the latest node version ([PR](nodejs/node#35399)). Meaning that the typeof `console` is `console` and Jest doesn't know how to mock a value of type `console`.

This diff manually mocks the `console` object to avoid this issue (verified with using Node 15 locally). However, the tests then started failing because the `close` event of streams was emitted more than once by our memory fs implementation.

The issue is that our `createWriteStream` implementetion does not specify the `emitClose: false` when creating the stream as required according to the [docs](https://nodejs.org/api/fs.html#fs_fs_createwritestream_path_options):

> By default, the stream will not emit a 'close' event after it has been destroyed. This is the opposite of the default for other Writable streams. Set the emitClose option to true to change this behavior.

I changed that in our `memory-fs` implementation and removed the manual emit of the `close` event. I then had to change the tests because the order of the events is `end`, `finish`, `close` and the tests asserted in the `end` event.

The tests then started passing on Node 15 but, surprise, they now failed on Node 12...

The reason is that the [`stream.Writeable`](https://nodejs.org/docs/latest-v13.x/api/stream.html#stream_constructor_new_stream_writable_options) option `autoDestroy` has changed with Node13 from default false to default true. Hardcoding `default: true` finally makes all tests passing on Node 12 - 15.

Reviewed By: cpojer

Differential Revision: D25495034

fbshipit-source-id: fdf871fa4dfbec079bc9ec1843fcff7facb3e0be

packages/buck-worker-tool/src/__tests__/worker-test.js

@@ -124,7 +124,7 @@ describe('Buck worker:', () => {
       fs.createWriteStream = (...args) => {
         const writeStream = createWriteStreamImpl(...args);
         ++openedStreams;
-        writeStream.on('close', () => --openedStreams);
+        writeStream.on('finish', () => --openedStreams);
         return writeStream;
       };
     });

packages/metro-memory-fs/src/__tests__/index-test.js

@@ -103,32 +103,32 @@ describe('posix support', () => {
 
   describe('createWriteStream', () => {
     it('writes a file', done => {
-      const st = fs.createWriteStream('/foo.txt');
+      const st = fs.createWriteStream('/foo.txt', {emitClose: true});
       let opened = false;
       let closed = false;
       st.on('open', () => (opened = true));
       st.on('close', () => (closed = true));
       st.write('test');
       st.write(' foo');
-      st.end(() => {
+      st.end();
+
+      st.on('close', () => {
         expect(opened).toBe(true);
         expect(closed).toBe(true);
         expect(fs.readFileSync('/foo.txt', 'utf8')).toEqual('test foo');
+
         done();
       });
     });
 
     it('writes a file, as buffer', done => {
       const st = fs.createWriteStream('/foo.txt');
       let opened = false;
-      let closed = false;
       st.on('open', () => (opened = true));
-      st.on('close', () => (closed = true));
       st.write(Buffer.from('test'));
       st.write(Buffer.from(' foo'));
       st.end(() => {
         expect(opened).toBe(true);
-        expect(closed).toBe(true);
         expect(fs.readFileSync('/foo.txt', 'utf8')).toEqual('test foo');
         done();
       });
@@ -138,13 +138,10 @@ describe('posix support', () => {
       fs.writeFileSync('/foo.txt', 'test bar');
       const st = fs.createWriteStream('/foo.txt', {start: 5, flags: 'r+'});
       let opened = false;
-      let closed = false;
       st.on('open', () => (opened = true));
-      st.on('close', () => (closed = true));
       st.write('beep');
       st.end(() => {
         expect(opened).toBe(true);
-        expect(closed).toBe(true);
         expect(fs.readFileSync('/foo.txt', 'utf8')).toEqual('test beep');
         done();
       });
@@ -154,13 +151,10 @@ describe('posix support', () => {
       const fd = fs.openSync('/bar.txt', 'w');
       const st = fs.createWriteStream('/foo.txt', {fd});
       let opened = false;
-      let closed = false;
       st.on('open', () => (opened = true));
-      st.on('close', () => (closed = true));
       st.write('beep boop');
       st.end(() => {
         expect(opened).toBe(false);
-        expect(closed).toBe(true);
         expect(fs.readFileSync('/bar.txt', 'utf8')).toEqual('beep boop');
         done();
       });

packages/metro-memory-fs/src/index.js

@@ -1027,6 +1027,7 @@ class MemoryFs {
           flags?: string,
           mode?: number,
           start?: number,
+          emitClose?: boolean,
           ...
         }
       | Encoding,
@@ -1037,30 +1038,36 @@ class MemoryFs {
           autoClose?: boolean,
           encoding?: Encoding,
           fd?: ?number,
+          emitClose?: boolean,
           flags?: string,
           mode?: number,
           start?: number,
           ...
         }
       | Encoding,
   ) => {
-    let autoClose, fd, flags, mode, start;
+    let autoClose, fd, flags, mode, start, emitClose;
     if (typeof options !== 'string' && options != null) {
-      ({autoClose, fd, flags, mode, start} = options);
+      ({autoClose, fd, flags, mode, start, emitClose} = options);
     }
     let st = null;
     if (fd == null) {
       fd = this._open(pathStr(filePath), flags || 'w', mode);
       process.nextTick(() => (st: any).emit('open', fd));
     }
     const ffd = fd;
-    const ropt = {fd, writeSync: this._write.bind(this), filePath, start};
+    const ropt = {
+      fd,
+      writeSync: this._write.bind(this),
+      filePath,
+      start,
+      emitClose: emitClose ?? false,
+    };
     const rst = new WriteFileStream(ropt);
     st = rst;
     if (autoClose !== false) {
       const doClose = () => {
         this.closeSync(ffd);
-        rst.emit('close');
       };
       rst.on('finish', doClose);
       rst.on('error', doClose);
@@ -1570,9 +1577,10 @@ class WriteFileStream extends stream.Writable {
     filePath: FilePath,
     writeSync: WriteSync,
     start?: number,
+    emitClose?: boolean,
     ...
   }) {
-    super();
+    super({emitClose: opts.emitClose, autoDestroy: true});
     this.path = opts.filePath;
     this.bytesWritten = 0;
     this._fd = opts.fd;