fs: restore JS implementation of realpath

This reverts parts of https://github.com/nodejs/node/commit/b488b19eaf2b2e7a3ca5eccd2445e245847a5f76
restoring javascript implementation of realpath and realpathSync.

Fixes: https://github.com/nodejs/node/issues/7175
Fixes: https://github.com/nodejs/node/issues/6861
Fixes: https://github.com/nodejs/node/issues/7294
Fixes: https://github.com/nodejs/node/issues/7192
Fixes: https://github.com/nodejs/node/issues/7044
Fixes: https://github.com/nodejs/node/issues/6624
Fixes: https://github.com/nodejs/node/issues/6978
PR-URL: https://github.com/nodejs/node/pull/7899
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>

1 files changed, 53 insertions, 0 deletions

diff --git a/test/parallel/test-fs-realpath-on-substed-drive.js b/test/parallel/test-fs-realpath-on-substed-drive.js
new file mode 100644
index 0000000000..c910936269
--- /dev/null
+++ b/test/parallel/test-fs-realpath-on-substed-drive.js
@@ -0,0 +1,53 @@
+'use strict';
+
+const common = require('../common');
+const assert = require('assert');
+const fs = require('fs');
+const spawnSync = require('child_process').spawnSync;
+
+if (!common.isWindows) {
+  common.skip('Test for Windows only');
+  return;
+}
+let result;
+
+// create a subst drive
+const driveLetters = 'ABCDEFGHIJKLMNOPQRSTUWXYZ';
+let drive;
+for (var i = 0; i < driveLetters.length; ++i) {
+  drive = `${driveLetters[i]}:`;
+  result = spawnSync('subst', [drive, common.fixturesDir]);
+  if (result.status === 0)
+    break;
+}
+if (i === driveLetters.length) {
+  common.skip('Cannot create subst drive');
+  return;
+}
+
+// schedule cleanup (and check if all callbacks where called)
+process.on('exit', function() {
+  spawnSync('subst', ['/d', drive]);
+});
+
+// test:
+const filename = `${drive}\\empty.js`;
+const filenameBuffer = Buffer.from(filename);
+
+result = fs.realpathSync(filename);
+assert.strictEqual(result, filename);
+
+result = fs.realpathSync(filename, 'buffer');
+assert(Buffer.isBuffer(result));
+assert(result.equals(filenameBuffer));
+
+fs.realpath(filename, common.mustCall(function(err, result) {
+  assert(!err);
+  assert.strictEqual(result, filename);
+}));
+
+fs.realpath(filename, 'buffer', common.mustCall(function(err, result) {
+  assert(!err);
+  assert(Buffer.isBuffer(result));
+  assert(result.equals(filenameBuffer));
+}));