fs: add autoClose option to fs.createWriteStream

doc/api/fs.markdown

@@ -334,13 +334,20 @@ Returns a new [`WriteStream`][] object. (See [Writable Stream][]).
     { flags: 'w',
       defaultEncoding: 'utf8',
       fd: null,
-      mode: 0o666 }
+      mode: 0o666,
+      autoClose: true }
 
 `options` may also include a `start` option to allow writing data at
 some position past the beginning of the file.  Modifying a file rather
 than replacing it may require a `flags` mode of `r+` rather than the
 default mode `w`. The `defaultEncoding` can be any one of those accepted by [`Buffer`][].
 
+If `autoClose` is set to true (default behavior) on `error` or `end`
+the file descriptor will be closed automatically. If `autoClose` is false,
+then the file descriptor won't be closed, even if there's an error.
+It is your responsiblity to close it and make sure
+there's no file descriptor leak.
+
 Like [`ReadStream`][], if `fd` is specified, `WriteStream` will ignore the
 `path` argument and will use the specified file descriptor. This means that no
 `'open'` event will be emitted. Note that `fd` should be blocking; non-blocking

lib/fs.js

@@ -1886,6 +1886,7 @@ function WriteStream(path, options) {
   this.mode = options.mode === undefined ? 0o666 : options.mode;
 
   this.start = options.start;
+  this.autoClose = options.autoClose === undefined ? true : !!options.autoClose;
   this.pos = undefined;
   this.bytesWritten = 0;
 
@@ -1907,7 +1908,11 @@ function WriteStream(path, options) {
     this.open();
 
   // dispose on finish.
-  this.once('finish', this.close);
+  this.once('finish', function() {
+    if (this.autoClose) {
+      this.close();
+    }
+  });
 }
 
 fs.FileWriteStream = fs.WriteStream; // support the legacy name
@@ -1916,7 +1921,9 @@ fs.FileWriteStream = fs.WriteStream; // support the legacy name
 WriteStream.prototype.open = function() {
   fs.open(this.path, this.flags, this.mode, function(er, fd) {
     if (er) {
-      this.destroy();
+      if (this.autoClose) {
+        this.destroy();
+      }
       this.emit('error', er);
       return;
     }
@@ -1939,7 +1946,9 @@ WriteStream.prototype._write = function(data, encoding, cb) {
   var self = this;
   fs.write(this.fd, data, 0, data.length, this.pos, function(er, bytes) {
     if (er) {
-      self.destroy();
+      if (self.autoClose) {
+        self.destroy();
+      }
       return cb(er);
     }
     self.bytesWritten += bytes;

test/parallel/test-fs-write-stream-autoclose-option.js

@@ -0,0 +1,52 @@
+'use strict';
+const common = require('../common');
+const assert = require('assert');
+const path = require('path');
+const fs = require('fs');
+
+const file = path.join(common.tmpDir, 'write-autoclose-opt1.txt');
+common.refreshTmpDir();
+let stream = fs.createWriteStream(file, {flags: 'w+', autoClose: false});
+stream.write('Test1');
+stream.end();
+stream.on('finish', common.mustCall(function() {
+  process.nextTick(common.mustCall(function() {
+    assert.strictEqual(stream.closed, undefined);
+    assert(stream.fd !== null);
+    next();
+  }));
+}));
+
+function next() {
+  // This will tell us if the fd is usable again or not
+  stream = fs.createWriteStream(null, {fd: stream.fd, start: 0});
+  stream.write('Test2');
+  stream.end();
+  stream.on('finish', common.mustCall(function() {
+    assert.strictEqual(stream.closed, true);
+    assert.strictEqual(stream.fd, null);
+    process.nextTick(common.mustCall(next2));
+  }));
+}
+
+function next2() {
+  // This will test if after reusing the fd data is written properly
+  fs.readFile(file, function(err, data) {
+    assert(!err);
+    assert.strictEqual(data.toString(), 'Test2');
+    process.nextTick(common.mustCall(next3));
+  });
+}
+
+function next3() {
+  // This is to test success scenario where autoClose is true
+  const stream = fs.createWriteStream(file, {autoClose: true});
+  stream.write('Test3');
+  stream.end();
+  stream.on('finish', common.mustCall(function() {
+    process.nextTick(common.mustCall(function() {
+      assert.strictEqual(stream.closed, true);
+      assert.strictEqual(stream.fd, null);
+    }));
+  }));
+}