windows: make symlinks tolerant to forward slashes

Closes #3440

lib/fs.js

@@ -532,25 +532,35 @@ fs.readlinkSync = function(path) {
   return binding.readlink(pathModule._makeLong(path));
 };
 
+function preprocessSymlinkDestination(path, type) {
+  if (!isWindows) {
+    // No preprocessing is needed on Unix.
+    return path;
+  } else if (type === 'junction') {
+    // Junctions paths need to be absolute and \\?\-prefixed.
+    return pathModule._makeLong(path);
+  } else {
+    // Windows symlinks don't tolerate forward slashes.
+    return ('' + path).replace(/\//g, '\\');
+  }
+}
+
 fs.symlink = function(destination, path, type_, callback) {
-  var type = (typeof(type_) == 'string' ? type_ : null);
+  var type = (typeof type_ === 'string' ? type_ : null);
   var callback = makeCallback(arguments[arguments.length - 1]);
 
-  if (isWindows && type === 'junction') {
+  binding.symlink(preprocessSymlinkDestination(destination),
-    destination = pathModule._makeLong(destination);
+                  pathModule._makeLong(path),
-  }
+                  type,
-
+                  callback);
-  binding.symlink(destination,
-                  pathModule._makeLong(path), type, callback);
 };
 
 fs.symlinkSync = function(destination, path, type) {
-  if (isWindows && type === 'junction') {
+  type = (typeof type === 'string' ? type : null);
-    destination = pathModule._makeLong(destination);
-  }
 
-  return binding.symlink(destination,
+  return binding.symlink(preprocessSymlinkDestination(destination),
-                         pathModule._makeLong(path), type);
+                         pathModule._makeLong(path),
+                         type);
 };
 
 fs.link = function(srcpath, dstpath, callback) {

test/simple/test-fs-realpath.js

@@ -33,14 +33,6 @@ if (isWindows) {
   // something like "C:\\"
   root = process.cwd().substr(0, 3);
 
-  // Symlinks MUST use \ paths, never / paths.
-  fs._symlinkSync = fs.symlinkSync;
-  fs.symlinkSync = function(a, b, type) {
-    a = a.split('/').join('\\');
-    b = b.split('/').join('\\');
-    return fs._symlinkSync(a, b, type);
-  };
-
   // On Windows, creating symlinks requires admin privileges.
   // We'll only try to run symlink test if we have enough privileges.
   try {