stream: add stream.pipeline and stream.onEnd

doc/api/errors.md

@@ -1423,6 +1423,12 @@ An attempt was made to call [`stream.pipe()`][] on a [`Writable`][] stream.
 
 An attempt was made to call [`stream.write()`][] with a `null` chunk.
 
+<a id="ERR_STREAM_PREMATURE_CLOSE"></a>
+### ERR_STREAM_PREMATURE_CLOSE
+
+An error returned by `stream.finished()` and `stream.pipeline()`, when a stream
+or a pipeline ends non gracefully with no explicit error.
+
 <a id="ERR_STREAM_PUSH_AFTER_EOF"></a>
 ### ERR_STREAM_PUSH_AFTER_EOF
 

doc/api/stream.md

@@ -46,6 +46,9 @@ There are four fundamental stream types within Node.js:
 * [Transform][] - Duplex streams that can modify or transform the data as it
   is written and read (for example [`zlib.createDeflate()`][]).
 
+Additionally this module includes the utility functions [pipeline][] and
+[finished][].
+
 ### Object Mode
 
 All streams created by Node.js APIs operate exclusively on strings and `Buffer`
@@ -1283,6 +1286,107 @@ implementors should not override this method, but instead implement
 [`readable._destroy`][readable-_destroy].
 The default implementation of `_destroy` for `Transform` also emit `'close'`.
 
+### stream.finished(stream, callback)
+<!-- YAML
+added: REPLACEME
+-->
+
+* `stream` {Stream} A readable and/or writable stream.
+* `callback` {Function} A callback function that takes an optional error
+  argument.
+
+A function to get notified when a stream is no longer readable, writable
+or has experienced an error or a premature close event.
+
+```js
+const { finished } = require('stream');
+
+const rs = fs.createReadStream('archive.tar');
+
+finished(rs, (err) => {
+  if (err) {
+    console.error('Stream failed', err);
+  } else {
+    console.log('Stream is done reading');
+  }
+});
+
+rs.resume(); // drain the stream
+```
+
+Especially useful in error handling scenarios where a stream is destroyed
+prematurely (like an aborted HTTP request), and will not emit `'end'`
+or `'finish'`.
+
+The `finished` API is promisify'able as well;
+
+```js
+const finished = util.promisify(stream.finished);
+
+const rs = fs.createReadStream('archive.tar');
+
+async function run() {
+  await finished(rs);
+  console.log('Stream is done reading');
+}
+
+run().catch(console.error);
+rs.resume(); // drain the stream
+```
+
+### stream.pipeline(...streams[, callback])
+<!-- YAML
+added: REPLACEME
+-->
+
+* `...streams` {Stream} Two or more streams to pipe between.
+* `callback` {Function} A callback function that takes an optional error
+  argument.
+
+A module method to pipe between streams forwarding errors and properly cleaning
+up and provide a callback when the pipeline is complete.
+
+```js
+const { pipeline } = require('stream');
+const fs = require('fs');
+const zlib = require('zlib');
+
+// Use the pipeline API to easily pipe a series of streams
+// together and get notified when the pipeline is fully done.
+
+// A pipeline to gzip a potentially huge tar file efficiently:
+
+pipeline(
+  fs.createReadStream('archive.tar'),
+  zlib.createGzip(),
+  fs.createWriteStream('archive.tar.gz'),
+  (err) => {
+    if (err) {
+      console.error('Pipeline failed', err);
+    } else {
+      console.log('Pipeline succeeded');
+    }
+  }
+);
+```
+
+The `pipeline` API is promisify'able as well:
+
+```js
+const pipeline = util.promisify(stream.pipeline);
+
+async function run() {
+  await pipeline(
+    fs.createReadStream('archive.tar'),
+    zlib.createGzip(),
+    fs.createWriteStream('archive.tar.gz')
+  );
+  console.log('Pipeline succeeded');
+}
+
+run().catch(console.error);
+```
+
 ## API for Stream Implementers
 
 <!--type=misc-->
@@ -2395,6 +2499,8 @@ contain multi-byte characters.
 [http-incoming-message]: http.html#http_class_http_incomingmessage
 [zlib]: zlib.html
 [hwm-gotcha]: #stream_highwatermark_discrepancy_after_calling_readable_setencoding
+[pipeline]: #stream_stream_pipeline_streams_callback
+[finished]: #stream_stream_finished_stream_callback
 [stream-_flush]: #stream_transform_flush_callback
 [stream-_read]: #stream_readable_read_size_1
 [stream-_transform]: #stream_transform_transform_chunk_encoding_callback

lib/internal/errors.js

@@ -895,6 +895,7 @@ E('ERR_STDOUT_CLOSE', 'process.stdout cannot be closed', Error);
 E('ERR_STREAM_CANNOT_PIPE', 'Cannot pipe, not readable', Error);
 E('ERR_STREAM_DESTROYED', 'Cannot call %s after a stream was destroyed', Error);
 E('ERR_STREAM_NULL_VALUES', 'May not write null values to stream', TypeError);
+E('ERR_STREAM_PREMATURE_CLOSE', 'Premature close', Error);
 E('ERR_STREAM_PUSH_AFTER_EOF', 'stream.push() after EOF', Error);
 E('ERR_STREAM_UNSHIFT_AFTER_END_EVENT',
   'stream.unshift() after end event', Error);

lib/internal/streams/end-of-stream.js

@@ -0,0 +1,96 @@
+// Ported from https://github.com/mafintosh/end-of-stream with
+// permission from the author, Mathias Buus (@mafintosh).
+
+'use strict';
+
+const {
+  ERR_STREAM_PREMATURE_CLOSE
+} = require('internal/errors').codes;
+
+function noop() {}
+
+function isRequest(stream) {
+  return stream.setHeader && typeof stream.abort === 'function';
+}
+
+function once(callback) {
+  let called = false;
+  return function(err) {
+    if (called) return;
+    called = true;
+    callback.call(this, err);
+  };
+}
+
+function eos(stream, opts, callback) {
+  if (typeof opts === 'function') return eos(stream, null, opts);
+  if (!opts) opts = {};
+
+  callback = once(callback || noop);
+
+  const ws = stream._writableState;
+  const rs = stream._readableState;
+  let readable = opts.readable || (opts.readable !== false && stream.readable);
+  let writable = opts.writable || (opts.writable !== false && stream.writable);
+
+  const onlegacyfinish = () => {
+    if (!stream.writable) onfinish();
+  };
+
+  const onfinish = () => {
+    writable = false;
+    if (!readable) callback.call(stream);
+  };
+
+  const onend = () => {
+    readable = false;
+    if (!writable) callback.call(stream);
+  };
+
+  const onerror = (err) => {
+    callback.call(stream, err);
+  };
+
+  const onclose = () => {
+    if (readable && !(rs && rs.ended)) {
+      return callback.call(stream, new ERR_STREAM_PREMATURE_CLOSE());
+    }
+    if (writable && !(ws && ws.ended)) {
+      return callback.call(stream, new ERR_STREAM_PREMATURE_CLOSE());
+    }
+  };
+
+  const onrequest = () => {
+    stream.req.on('finish', onfinish);
+  };
+
+  if (isRequest(stream)) {
+    stream.on('complete', onfinish);
+    stream.on('abort', onclose);
+    if (stream.req) onrequest();
+    else stream.on('request', onrequest);
+  } else if (writable && !ws) { // legacy streams
+    stream.on('end', onlegacyfinish);
+    stream.on('close', onlegacyfinish);
+  }
+
+  stream.on('end', onend);
+  stream.on('finish', onfinish);
+  if (opts.error !== false) stream.on('error', onerror);
+  stream.on('close', onclose);
+
+  return function() {
+    stream.removeListener('complete', onfinish);
+    stream.removeListener('abort', onclose);
+    stream.removeListener('request', onrequest);
+    if (stream.req) stream.req.removeListener('finish', onfinish);
+    stream.removeListener('end', onlegacyfinish);
+    stream.removeListener('close', onlegacyfinish);
+    stream.removeListener('finish', onfinish);
+    stream.removeListener('end', onend);
+    stream.removeListener('error', onerror);
+    stream.removeListener('close', onclose);
+  };
+}
+
+module.exports = eos;

lib/internal/streams/pipeline.js

@@ -0,0 +1,95 @@
+// Ported from https://github.com/mafintosh/pump with
+// permission from the author, Mathias Buus (@mafintosh).
+
+'use strict';
+
+const eos = require('internal/streams/end-of-stream');
+
+const {
+  ERR_MISSING_ARGS,
+  ERR_STREAM_DESTROYED
+} = require('internal/errors').codes;
+
+function once(callback) {
+  let called = false;
+  return function(err) {
+    if (called) return;
+    called = true;
+    callback(err);
+  };
+}
+
+function noop() {}
+
+function isRequest(stream) {
+  return stream.setHeader && typeof stream.abort === 'function';
+}
+
+function destroyer(stream, reading, writing, callback) {
+  callback = once(callback);
+
+  let closed = false;
+  stream.on('close', () => {
+    closed = true;
+  });
+
+  eos(stream, { readable: reading, writable: writing }, (err) => {
+    if (err) return callback(err);
+    closed = true;
+    callback();
+  });
+
+  let destroyed = false;
+  return (err) => {
+    if (closed) return;
+    if (destroyed) return;
+    destroyed = true;
+
+    // request.destroy just do .end - .abort is what we want
+    if (isRequest(stream)) return stream.abort();
+    if (typeof stream.destroy === 'function') return stream.destroy();
+
+    callback(err || new ERR_STREAM_DESTROYED('pipe'));
+  };
+}
+
+function call(fn) {
+  fn();
+}
+
+function pipe(from, to) {
+  return from.pipe(to);
+}
+
+function popCallback(streams) {
+  if (!streams.length) return noop;
+  if (typeof streams[streams.length - 1] !== 'function') return noop;
+  return streams.pop();
+}
+
+function pipeline(...streams) {
+  const callback = popCallback(streams);
+
+  if (Array.isArray(streams[0])) streams = streams[0];
+
+  if (streams.length < 2) {
+    throw new ERR_MISSING_ARGS('streams');
+  }
+
+  let error;
+  const destroys = streams.map(function(stream, i) {
+    const reading = i < streams.length - 1;
+    const writing = i > 0;
+    return destroyer(stream, reading, writing, function(err) {
+      if (!error) error = err;
+      if (err) destroys.forEach(call);
+      if (reading) return;
+      destroys.forEach(call);
+      callback(error);
+    });
+  });
+
+  return streams.reduce(pipe);
+}
+
+module.exports = pipeline;

lib/stream.js

@@ -22,6 +22,8 @@
 'use strict';
 
 const { Buffer } = require('buffer');
+const pipeline = require('internal/streams/pipeline');
+const eos = require('internal/streams/end-of-stream');
 
 // Note: export Stream before Readable/Writable/Duplex/...
 // to avoid a cross-reference(require) issues
@@ -33,6 +35,9 @@ Stream.Duplex = require('_stream_duplex');
 Stream.Transform = require('_stream_transform');
 Stream.PassThrough = require('_stream_passthrough');
 
+Stream.pipeline = pipeline;
+Stream.finished = eos;
+
 // Backwards-compat with node 0.4.x
 Stream.Stream = Stream;
 

node.gyp

@@ -154,6 +154,8 @@
       'lib/internal/streams/legacy.js',
       'lib/internal/streams/destroy.js',
       'lib/internal/streams/state.js',
+      'lib/internal/streams/pipeline.js',
+      'lib/internal/streams/end-of-stream.js',
       'lib/internal/wrap_js_stream.js',
       'deps/v8/tools/splaytree.js',
       'deps/v8/tools/codemap.js',