fs,doc,test: open reserved characters under win32

doc/api/fs.md

@@ -1587,6 +1587,26 @@ fs.open('<directory>', 'a+', (err, fd) => {
 });
 ```
 
+Some characters are reserved under Windows as documented by
+[Naming Files, Paths, and Namespaces][]. Under NTFS, if the filename contains
+colon, Node.js will open a file system stream, as described by
+[this MSDN page][MSDN-Using-Streams].
+
+The reserved characters are list below.
+
++ `<` (less than)
++ `>` (greater than)
++ `:` (colon)
++ `"` (double quote)
++ `/` (forward slash)
++ `\` (backslash)
++ `|` (vertical bar or pipe)
++ `?` (question mark)
++ `*` (asterisk)
+
+Functions based on `fs.open()` exhibit this behavior as well. eg.
+`fs.writeFile()`, `fs.readFile()`, etc.
+
 ## fs.openSync(path, flags[, mode])
 <!-- YAML
 added: v0.1.21
@@ -2864,3 +2884,5 @@ The following constants are meant for use with the [`fs.Stats`][] object's
 [Readable Stream]: stream.html#stream_class_stream_readable
 [Writable Stream]: stream.html#stream_class_stream_writable
 [inode]: https://en.wikipedia.org/wiki/Inode
+[Naming Files, Paths, and Namespaces]: https://msdn.microsoft.com/en-us/library/windows/desktop/aa365247(v=vs.85).aspx
+[MSDN-Using-Streams]: https://msdn.microsoft.com/en-us/library/windows/desktop/bb540537.aspx

test/parallel/test-fs-write-file-invalid-path.js

@@ -0,0 +1,45 @@
+'use strict';
+
+const common = require('../common');
+const assert = require('assert');
+const fs = require('fs');
+const path = require('path');
+
+if (!common.isWindows)
+  common.skip('This test is for Windows only.');
+
+common.refreshTmpDir();
+
+const DATA_VALUE = 'hello';
+
+// Refs: https://msdn.microsoft.com/en-us/library/windows/desktop/aa365247(v=vs.85).aspx
+// Ignore '/', '\\' and ':'
+const REVERSED_CHARACTERS = '<>"|?*';
+
+Array.prototype.forEach.call(REVERSED_CHARACTERS, (ch) => {
+  const pathname = path.join(common.tmpDir, `somefile_${ch}`);
+  assert.throws(
+    () => {
+      fs.writeFileSync(pathname, DATA_VALUE);
+    },
+    /^Error: ENOENT: no such file or directory, open '.*'$/,
+    `failed with '${ch}'`);
+});
+
+// Test for ':' (NTFS data streams).
+// Refs: https://msdn.microsoft.com/en-us/library/windows/desktop/bb540537.aspx
+const pathname = path.join(common.tmpDir, 'foo:bar');
+fs.writeFileSync(pathname, DATA_VALUE);
+
+let content = '';
+const fileDataStream = fs.createReadStream(pathname, {
+  encoding: 'utf8'
+});
+
+fileDataStream.on('data', (data) => {
+  content += data.toString();
+});
+
+fileDataStream.on('end', common.mustCall(() => {
+  assert.strictEqual(content, DATA_VALUE);
+}));