stream: add destroy and _destroy methods.

Adds destroy() and _destroy() methods to Readable, Writable, Duplex
and Transform. It also standardizes the behavior and the implementation
of destroy(), which has been inconsistent in userland and core.
This PR also updates all the subsystems of core to use the new
destroy().

PR-URL: #12925
Reviewed-By: James M Snell <[email protected]>
Reviewed-By: Calvin Metcalf <[email protected]>
Reviewed-By: Colin Ihrig <[email protected]>

doc/api/stream.md

@@ -499,6 +499,15 @@ write('hello', () => {
 
 A Writable stream in object mode will always ignore the `encoding` argument.
 
+##### writable.destroy([error])
+<!-- YAML
+added: REPLACEME
+-->
+
+Destroy the stream, and emit the passed error. After this call, the
+writible stream has ended. Implementors should not override this method,
+but instead implement [`writable._destroy`][writable-_destroy].
+
 ### Readable Streams
 
 Readable streams are an abstraction for a *source* from which data is
@@ -1070,6 +1079,16 @@ myReader.on('readable', () => {
 });
 ```
 
+##### readable.destroy([error])
+<!-- YAML
+added: REPLACEME
+-->
+
+Destroy the stream, and emit `'error'`. After this call, the
+readable stream will release any internal resources.
+Implementors should not override this method, but instead implement
+[`readable._destroy`][readable-_destroy].
+
 ### Duplex and Transform Streams
 
 #### Class: stream.Duplex
@@ -1109,6 +1128,16 @@ Examples of Transform streams include:
 * [zlib streams][zlib]
 * [crypto streams][crypto]
 
+##### transform.destroy([error])
+<!-- YAML
+added: REPLACEME
+-->
+
+Destroy the stream, and emit `'error'`. After this call, the
+transform stream would release any internal resources.
+implementors should not override this method, but instead implement
+[`readable._destroy`][readable-_destroy].
+The default implementation of `_destroy` for `Transform` also emit `'close'`.
 
 ## API for Stream Implementers
 
@@ -1247,6 +1276,8 @@ constructor and implement the `writable._write()` method. The
     [`stream._write()`][stream-_write] method.
   * `writev` {Function} Implementation for the
     [`stream._writev()`][stream-_writev] method.
+  * `destroy` {Function} Implementation for the
+    [`stream._destroy()`][writable-_destroy] method.
 
 For example:
 
@@ -1356,6 +1387,15 @@ The `writable._writev()` method is prefixed with an underscore because it is
 internal to the class that defines it, and should never be called directly by
 user programs.
 
+#### writable.\_destroy(err, callback)
+<!-- YAML
+added: REPLACEME
+-->
+
+* `err` {Error} An error.
+* `callback` {Function} A callback function that takes an optional error argument
+  which is invoked when the writable is destroyed.
+
 #### Errors While Writing
 
 It is recommended that errors occurring during the processing of the
@@ -1425,6 +1465,8 @@ constructor and implement the `readable._read()` method.
     a single value instead of a Buffer of size n. Defaults to `false`
   * `read` {Function} Implementation for the [`stream._read()`][stream-_read]
     method.
+  * `destroy` {Function} Implementation for the [`stream._destroy()`][readable-_destroy]
+    method.
 
 For example:
 
@@ -2073,4 +2115,8 @@ readable buffer so there is nothing for a user to consume.
 [stream-read]: #stream_readable_read_size
 [stream-resume]: #stream_readable_resume
 [stream-write]: #stream_writable_write_chunk_encoding_callback
-[zlib]: zlib.html
+[readable-_destroy]: #stream_readable_destroy_err_callback
+[writable-_destroy]: #stream_writable_destroy_err_callback
+[TCP sockets]: net.html#net_class_net_socket
+[Transform]: #stream_class_stream_transform
+[Writable]: #stream_class_stream_writable

lib/_stream_duplex.js

@@ -76,3 +76,33 @@ function onend() {
 function onEndNT(self) {
   self.end();
 }
+
+Object.defineProperty(Duplex.prototype, 'destroyed', {
+  get() {
+    if (this._readableState === undefined ||
+        this._writableState === undefined) {
+      return false;
+    }
+    return this._readableState.destroyed && this._writableState.destroyed;
+  },
+  set(value) {
+    // we ignore the value if the stream
+    // has not been initialized yet
+    if (this._readableState === undefined ||
+        this._writableState === undefined) {
+      return;
+    }
+
+    // backward compatibility, the user is explicitly
+    // managing destroyed
+    this._readableState.destroyed = value;
+    this._writableState.destroyed = value;
+  }
+});
+
+Duplex.prototype._destroy = function(err, cb) {
+  this.push(null);
+  this.end();
+
+  process.nextTick(cb, err);
+};

lib/_stream_readable.js

@@ -30,6 +30,7 @@ const Buffer = require('buffer').Buffer;
 const util = require('util');
 const debug = util.debuglog('stream');
 const BufferList = require('internal/streams/BufferList');
+const destroyImpl = require('internal/streams/destroy');
 var StringDecoder;
 
 util.inherits(Readable, Stream);
@@ -99,6 +100,9 @@ function ReadableState(options, stream) {
   this.readableListening = false;
   this.resumeScheduled = false;
 
+  // has it been destroyed
+  this.destroyed = false;
+
   // Crypto is kind of old and crusty.  Historically, its default string
   // encoding is 'binary' so we have to make this configurable.
   // Everything else in the universe uses 'utf8', though.
@@ -129,12 +133,44 @@ function Readable(options) {
   // legacy
   this.readable = true;
 
-  if (options && typeof options.read === 'function')
-    this._read = options.read;
+  if (options) {
+    if (typeof options.read === 'function')
+      this._read = options.read;
+
+    if (typeof options.destroy === 'function')
+      this._destroy = options.destroy;
+  }
 
   Stream.call(this);
 }
 
+Object.defineProperty(Readable.prototype, 'destroyed', {
+  get() {
+    if (this._readableState === undefined) {
+      return false;
+    }
+    return this._readableState.destroyed;
+  },
+  set(value) {
+    // we ignore the value if the stream
+    // has not been initialized yet
+    if (!this._readableState) {
+      return;
+    }
+
+    // backward compatibility, the user is explicitly
+    // managing destroyed
+    this._readableState.destroyed = value;
+  }
+});
+
+Readable.prototype.destroy = destroyImpl.destroy;
+Readable.prototype._undestroy = destroyImpl.undestroy;
+Readable.prototype._destroy = function(err, cb) {
+  this.push(null);
+  cb(err);
+};
+
 // Manually shove something into the read() buffer.
 // This returns true if the highWaterMark has not been hit yet,
 // similar to how Writable.write() returns true if you should

lib/_stream_transform.js

@@ -194,6 +194,14 @@ Transform.prototype._read = function(n) {
 };
 
 
+Transform.prototype._destroy = function(err, cb) {
+  Duplex.prototype._destroy.call(this, err, (err2) => {
+    cb(err2);
+    this.emit('close');
+  });
+};
+
+
 function done(stream, er, data) {
   if (er)
     return stream.emit('error', er);

lib/_stream_writable.js

@@ -32,6 +32,7 @@ const util = require('util');
 const internalUtil = require('internal/util');
 const Stream = require('stream');
 const Buffer = require('buffer').Buffer;
+const destroyImpl = require('internal/streams/destroy');
 
 util.inherits(Writable, Stream);
 
@@ -66,6 +67,9 @@ function WritableState(options, stream) {
   // when 'finish' is emitted
   this.finished = false;
 
+  // has it been destroyed
+  this.destroyed = false;
+
   // should we decode strings into buffers before passing to _write?
   // this is here so that some node-core streams can optimize string
   // handling at a lower level.
@@ -192,6 +196,9 @@ function Writable(options) {
 
     if (typeof options.writev === 'function')
       this._writev = options.writev;
+
+    if (typeof options.destroy === 'function')
+      this._destroy = options.destroy;
   }
 
   Stream.call(this);
@@ -563,3 +570,30 @@ function onCorkedFinish(corkReq, state, err) {
     state.corkedRequestsFree = corkReq;
   }
 }
+
+Object.defineProperty(Writable.prototype, 'destroyed', {
+  get() {
+    if (this._writableState === undefined) {
+      return false;
+    }
+    return this._writableState.destroyed;
+  },
+  set(value) {
+    // we ignore the value if the stream
+    // has not been initialized yet
+    if (!this._writableState) {
+      return;
+    }
+
+    // backward compatibility, the user is explicitly
+    // managing destroyed
+    this._writableState.destroyed = value;
+  }
+});
+
+Writable.prototype.destroy = destroyImpl.destroy;
+Writable.prototype._undestroy = destroyImpl.undestroy;
+Writable.prototype._destroy = function(err, cb) {
+  this.end();
+  cb(err);
+};

lib/fs.js

@@ -1986,11 +1986,10 @@ ReadStream.prototype._read = function(n) {
 };
 
 
-ReadStream.prototype.destroy = function() {
-  if (this.destroyed)
-    return;
-  this.destroyed = true;
-  this.close();
+ReadStream.prototype._destroy = function(err, cb) {
+  this.close(function(err2) {
+    cb(err || err2);
+  });
 };
 
 
@@ -2157,7 +2156,7 @@ WriteStream.prototype._writev = function(data, cb) {
 };
 
 
-WriteStream.prototype.destroy = ReadStream.prototype.destroy;
+WriteStream.prototype._destroy = ReadStream.prototype._destroy;
 WriteStream.prototype.close = ReadStream.prototype.close;
 
 // There is no shutdown() for files.

lib/internal/process/stdio.js

@@ -18,10 +18,12 @@ function setupStdio() {
   function getStdout() {
     if (stdout) return stdout;
     stdout = createWritableStdioStream(1);
-    stdout.destroy = stdout.destroySoon = function(er) {
+    stdout.destroySoon = stdout.destroy;
+    stdout._destroy = function(er, cb) {
+      // avoid errors if we already emitted
       const errors = lazyErrors();
       er = er || new errors.Error('ERR_STDOUT_CLOSE');
-      stdout.emit('error', er);
+      cb(er);
     };
     if (stdout.isTTY) {
       process.on('SIGWINCH', () => stdout._refreshSize());
@@ -32,10 +34,12 @@ function setupStdio() {
   function getStderr() {
     if (stderr) return stderr;
     stderr = createWritableStdioStream(2);
-    stderr.destroy = stderr.destroySoon = function(er) {
+    stderr.destroySoon = stderr.destroy;
+    stderr._destroy = function(er, cb) {
+      // avoid errors if we already emitted
       const errors = lazyErrors();
       er = er || new errors.Error('ERR_STDERR_CLOSE');
-      stderr.emit('error', er);
+      cb(er);
     };
     if (stderr.isTTY) {
       process.on('SIGWINCH', () => stderr._refreshSize());

lib/internal/streams/destroy.js

@@ -0,0 +1,65 @@
+'use strict';
+
+// undocumented cb() API, needed for core, not for public API
+function destroy(err, cb) {
+  const readableDestroyed = this._readableState &&
+    this._readableState.destroyed;
+  const writableDestroyed = this._writableState &&
+    this._writableState.destroyed;
+
+  if (readableDestroyed || writableDestroyed) {
+    if (err && (!this._writableState || !this._writableState.errorEmitted)) {
+      process.nextTick(emitErrorNT, this, err);
+    }
+    return;
+  }
+
+  // we set destroyed to true before firing error callbacks in order
+  // to make it re-entrance safe in case destroy() is called within callbacks
+
+  if (this._readableState) {
+    this._readableState.destroyed = true;
+  }
+
+  // if this is a duplex stream mark the writable part as destroyed as well
+  if (this._writableState) {
+    this._writableState.destroyed = true;
+  }
+
+  this._destroy(err || null, (err) => {
+    if (!cb && err) {
+      process.nextTick(emitErrorNT, this, err);
+      if (this._writableState) {
+        this._writableState.errorEmitted = true;
+      }
+    } else if (cb) {
+      cb(err);
+    }
+  });
+}
+
+function undestroy() {
+  if (this._readableState) {
+    this._readableState.destroyed = false;
+    this._readableState.reading = false;
+    this._readableState.ended = false;
+    this._readableState.endEmitted = false;
+  }
+
+  if (this._writableState) {
+    this._writableState.destroyed = false;
+    this._writableState.ended = false;
+    this._writableState.ending = false;
+    this._writableState.finished = false;
+    this._writableState.errorEmitted = false;
+  }
+}
+
+function emitErrorNT(self, err) {
+  self.emit('error', err);
+}
+
+module.exports = {
+  destroy,
+  undestroy
+};