fs: expose realpath(3) bindings

Make the `uv_fs_realpath()` binding (which calls the libc `realpath()`
on UNIX and `GetFinalPathNameByHandle()` on Windows) available as the
`fs.realpath.native()` and `fs.realpathSync.native()` functions.

The binding was already available as `process.binding('fs').realpath`
but was not exposed or tested - and partly broken as a result.

Fixes: https://github.com/nodejs/node/issues/8715
PR-URL: https://github.com/nodejs/node/pull/15776
Refs: https://github.com/nodejs/node/pull/7899
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com>
Reviewed-By: Minwoo Jung <minwoo@nodesource.com>
Reviewed-By: Trevor Norris <trev.norris@gmail.com>

4 files changed, 110 insertions, 87 deletions

diff --git a/lib/fs.js b/lib/fs.js
index e1407ba4f1..ce76ebc4d6 100644
--- a/lib/fs.js
+++ b/lib/fs.js
@@ -1722,6 +1722,14 @@ fs.realpathSync = function realpathSync(p, options) {
 };
 
 
+fs.realpathSync.native = function(path, options) {
+  options = getOptions(options, {});
+  handleError((path = getPathFromURL(path)));
+  nullCheck(path);
+  return binding.realpath(path, options.encoding);
+};
+
+
 fs.realpath = function realpath(p, options, callback) {
   callback = maybeCallback(typeof options === 'function' ? options : callback);
   if (!options)
@@ -1858,6 +1866,18 @@ fs.realpath = function realpath(p, options, callback) {
   }
 };
 
+
+fs.realpath.native = function(path, options, callback) {
+  callback = maybeCallback(callback || options);
+  options = getOptions(options, {});
+  if (handleError((path = getPathFromURL(path)), callback)) return;
+  if (!nullCheck(path, callback)) return;
+  const req = new FSReqWrap();
+  req.oncomplete = callback;
+  return binding.realpath(path, options.encoding, req);
+};
+
+
 fs.mkdtemp = function(prefix, options, callback) {
   callback = makeCallback(typeof options === 'function' ? options : callback);
   options = getOptions(options, {});
diff --git a/src/node_file.cc b/src/node_file.cc
index c657ece93f..5d06960953 100644
--- a/src/node_file.cc
+++ b/src/node_file.cc
@@ -827,24 +827,15 @@ static void MKDir(const FunctionCallbackInfo<Value>& args) {
 }
 
 static void RealPath(const FunctionCallbackInfo<Value>& args) {
+  CHECK_GE(args.Length(), 2);
   Environment* env = Environment::GetCurrent(args);
-
-  const int argc = args.Length();
-
-  if (argc < 1)
-    return TYPE_ERROR("path required");
-
   BufferValue path(env->isolate(), args[0]);
   ASSERT_PATH(path)
 
   const enum encoding encoding = ParseEncoding(env->isolate(), args[1], UTF8);
 
-  Local<Value> callback = Null(env->isolate());
-  if (argc == 3)
-    callback = args[2];
-
-  if (callback->IsObject()) {
-    ASYNC_CALL(realpath, callback, encoding, *path);
+  if (args[2]->IsObject()) {
+    ASYNC_CALL(realpath, args[2], encoding, *path);
   } else {
     SYNC_CALL(realpath, *path, *path);
     const char* link_path = static_cast<const char*>(SYNC_REQ.ptr);
diff --git a/test/parallel/test-fs-realpath-native.js b/test/parallel/test-fs-realpath-native.js
new file mode 100644
index 0000000000..43d6b8ca80
--- /dev/null
+++ b/test/parallel/test-fs-realpath-native.js
@@ -0,0 +1,12 @@
+'use strict';
+const common = require('../common');
+const assert = require('assert');
+const fs = require('fs');
+
+if (!common.isOSX) common.skip('MacOS-only test.');
+
+assert.strictEqual(fs.realpathSync.native('/users'), '/Users');
+fs.realpath.native('/users', common.mustCall((err, res) => {
+  assert.ifError(err);
+  assert.strictEqual(res, '/Users');
+}));
diff --git a/test/parallel/test-fs-realpath.js b/test/parallel/test-fs-realpath.js
index 3af0092f61..013e801514 100644
--- a/test/parallel/test-fs-realpath.js
+++ b/test/parallel/test-fs-realpath.js
@@ -94,19 +94,19 @@ function asynctest(testBlock, args, callback, assertBlock) {
 }
 
 // sub-tests:
-function test_simple_error_callback(cb) {
-  fs.realpath('/this/path/does/not/exist', common.mustCall(function(err, s) {
+function test_simple_error_callback(realpath, realpathSync, cb) {
+  realpath('/this/path/does/not/exist', common.mustCall(function(err, s) {
     assert(err);
     assert(!s);
     cb();
   }));
 }
 
-function test_simple_relative_symlink(callback) {
+function test_simple_relative_symlink(realpath, realpathSync, callback) {
   console.log('test_simple_relative_symlink');
   if (skipSymlinks) {
     common.printSkipMessage('symlink test (no privs)');
-    return runNextTest();
+    return callback();
   }
   const entry = `${tmpDir}/symlink`;
   const expected = `${tmpDir}/cycles/root.js`;
@@ -118,14 +118,14 @@ function test_simple_relative_symlink(callback) {
     fs.symlinkSync(t[1], t[0], 'file');
     unlink.push(t[0]);
   });
-  const result = fs.realpathSync(entry);
+  const result = realpathSync(entry);
   assertEqualPath(result, path.resolve(expected));
-  asynctest(fs.realpath, [entry], callback, function(err, result) {
+  asynctest(realpath, [entry], callback, function(err, result) {
     assertEqualPath(result, path.resolve(expected));
   });
 }
 
-function test_simple_absolute_symlink(callback) {
+function test_simple_absolute_symlink(realpath, realpathSync, callback) {
   console.log('test_simple_absolute_symlink');
 
   // this one should still run, even if skipSymlinks is set,
@@ -144,18 +144,18 @@ function test_simple_absolute_symlink(callback) {
     fs.symlinkSync(t[1], t[0], type);
     unlink.push(t[0]);
   });
-  const result = fs.realpathSync(entry);
+  const result = realpathSync(entry);
   assertEqualPath(result, path.resolve(expected));
-  asynctest(fs.realpath, [entry], callback, function(err, result) {
+  asynctest(realpath, [entry], callback, function(err, result) {
     assertEqualPath(result, path.resolve(expected));
   });
 }
 
-function test_deep_relative_file_symlink(callback) {
+function test_deep_relative_file_symlink(realpath, realpathSync, callback) {
   console.log('test_deep_relative_file_symlink');
   if (skipSymlinks) {
     common.printSkipMessage('symlink test (no privs)');
-    return runNextTest();
+    return callback();
   }
 
   const expected = fixtures.path('cycles', 'root.js');
@@ -175,17 +175,17 @@ function test_deep_relative_file_symlink(callback) {
   unlink.push(linkPath1);
   unlink.push(entry);
 
-  assertEqualPath(fs.realpathSync(entry), path.resolve(expected));
-  asynctest(fs.realpath, [entry], callback, function(err, result) {
+  assertEqualPath(realpathSync(entry), path.resolve(expected));
+  asynctest(realpath, [entry], callback, function(err, result) {
     assertEqualPath(result, path.resolve(expected));
   });
 }
 
-function test_deep_relative_dir_symlink(callback) {
+function test_deep_relative_dir_symlink(realpath, realpathSync, callback) {
   console.log('test_deep_relative_dir_symlink');
   if (skipSymlinks) {
     common.printSkipMessage('symlink test (no privs)');
-    return runNextTest();
+    return callback();
   }
   const expected = fixtures.path('cycles', 'folder');
   const path1b = path.join(targetsAbsDir, 'nested-index', 'one');
@@ -202,18 +202,18 @@ function test_deep_relative_dir_symlink(callback) {
   unlink.push(linkPath1b);
   unlink.push(entry);
 
-  assertEqualPath(fs.realpathSync(entry), path.resolve(expected));
+  assertEqualPath(realpathSync(entry), path.resolve(expected));
 
-  asynctest(fs.realpath, [entry], callback, function(err, result) {
+  asynctest(realpath, [entry], callback, function(err, result) {
     assertEqualPath(result, path.resolve(expected));
   });
 }
 
-function test_cyclic_link_protection(callback) {
+function test_cyclic_link_protection(realpath, realpathSync, callback) {
   console.log('test_cyclic_link_protection');
   if (skipSymlinks) {
     common.printSkipMessage('symlink test (no privs)');
-    return runNextTest();
+    return callback();
   }
   const entry = path.join(tmpDir, '/cycles/realpath-3a');
   [
@@ -226,24 +226,24 @@ function test_cyclic_link_protection(callback) {
     unlink.push(t[0]);
   });
   assert.throws(() => {
-    fs.realpathSync(entry);
+    realpathSync(entry);
   }, common.expectsError({ code: 'ELOOP', type: Error }));
   asynctest(
-    fs.realpath, [entry], callback, common.mustCall(function(err, result) {
+    realpath, [entry], callback, common.mustCall(function(err, result) {
       assert.strictEqual(err.path, entry);
       assert.strictEqual(result, undefined);
       return true;
     }));
 }
 
-function test_cyclic_link_overprotection(callback) {
+function test_cyclic_link_overprotection(realpath, realpathSync, callback) {
   console.log('test_cyclic_link_overprotection');
   if (skipSymlinks) {
     common.printSkipMessage('symlink test (no privs)');
-    return runNextTest();
+    return callback();
   }
   const cycles = `${tmpDir}/cycles`;
-  const expected = fs.realpathSync(cycles);
+  const expected = realpathSync(cycles);
   const folder = `${cycles}/folder`;
   const link = `${folder}/cycles`;
   let testPath = cycles;
@@ -251,17 +251,17 @@ function test_cyclic_link_overprotection(callback) {
   try { fs.unlinkSync(link); } catch (ex) {}
   fs.symlinkSync(cycles, link, 'dir');
   unlink.push(link);
-  assertEqualPath(fs.realpathSync(testPath), path.resolve(expected));
-  asynctest(fs.realpath, [testPath], callback, function(er, res) {
+  assertEqualPath(realpathSync(testPath), path.resolve(expected));
+  asynctest(realpath, [testPath], callback, function(er, res) {
     assertEqualPath(res, path.resolve(expected));
   });
 }
 
-function test_relative_input_cwd(callback) {
+function test_relative_input_cwd(realpath, realpathSync, callback) {
   console.log('test_relative_input_cwd');
   if (skipSymlinks) {
     common.printSkipMessage('symlink test (no privs)');
-    return runNextTest();
+    return callback();
   }
 
   // we need to calculate the relative path to the tmp dir from cwd
@@ -286,21 +286,21 @@ function test_relative_input_cwd(callback) {
 
   const origcwd = process.cwd();
   process.chdir(entrydir);
-  assertEqualPath(fs.realpathSync(entry), path.resolve(expected));
-  asynctest(fs.realpath, [entry], callback, function(err, result) {
+  assertEqualPath(realpathSync(entry), path.resolve(expected));
+  asynctest(realpath, [entry], callback, function(err, result) {
     process.chdir(origcwd);
     assertEqualPath(result, path.resolve(expected));
     return true;
   });
 }
 
-function test_deep_symlink_mix(callback) {
+function test_deep_symlink_mix(realpath, realpathSync, callback) {
   console.log('test_deep_symlink_mix');
   if (common.isWindows) {
     // This one is a mix of files and directories, and it's quite tricky
     // to get the file/dir links sorted out correctly.
     common.printSkipMessage('symlink test (no privs)');
-    return runNextTest();
+    return callback();
   }
 
   /*
@@ -339,22 +339,22 @@ function test_deep_symlink_mix(callback) {
     unlink.push(tmp('node-test-realpath-d2'));
   }
   const expected = `${tmpAbsDir}/cycles/root.js`;
-  assertEqualPath(fs.realpathSync(entry), path.resolve(expected));
-  asynctest(fs.realpath, [entry], callback, function(err, result) {
+  assertEqualPath(realpathSync(entry), path.resolve(expected));
+  asynctest(realpath, [entry], callback, function(err, result) {
     assertEqualPath(result, path.resolve(expected));
     return true;
   });
 }
 
-function test_non_symlinks(callback) {
+function test_non_symlinks(realpath, realpathSync, callback) {
   console.log('test_non_symlinks');
   const entrydir = path.dirname(tmpAbsDir);
   const entry = `${tmpAbsDir.substr(entrydir.length + 1)}/cycles/root.js`;
   const expected = `${tmpAbsDir}/cycles/root.js`;
   const origcwd = process.cwd();
   process.chdir(entrydir);
-  assertEqualPath(fs.realpathSync(entry), path.resolve(expected));
-  asynctest(fs.realpath, [entry], callback, function(err, result) {
+  assertEqualPath(realpathSync(entry), path.resolve(expected));
+  asynctest(realpath, [entry], callback, function(err, result) {
     process.chdir(origcwd);
     assertEqualPath(result, path.resolve(expected));
     return true;
@@ -362,19 +362,21 @@ function test_non_symlinks(callback) {
 }
 
 const upone = path.join(process.cwd(), '..');
-function test_escape_cwd(cb) {
+function test_escape_cwd(realpath, realpathSync, cb) {
   console.log('test_escape_cwd');
-  asynctest(fs.realpath, ['..'], cb, function(er, uponeActual) {
+  asynctest(realpath, ['..'], cb, function(er, uponeActual) {
     assertEqualPath(
       upone, uponeActual,
       `realpath("..") expected: ${path.resolve(upone)} actual:${uponeActual}`);
   });
 }
-const uponeActual = fs.realpathSync('..');
-assertEqualPath(
-  upone, uponeActual,
-  `realpathSync("..") expected: ${path.resolve(upone)} actual:${uponeActual}`);
 
+function test_upone_actual(realpath, realpathSync, cb) {
+  console.log('test_upone_actual');
+  const uponeActual = realpathSync('..');
+  assertEqualPath(upone, uponeActual);
+  cb();
+}
 
 // going up with .. multiple times
 // .
@@ -383,23 +385,13 @@ assertEqualPath(
 //     |   `-- e -> ..
 //     `-- d -> ..
 // realpath(a/b/e/d/a/b/e/d/a) ==> a
-function test_up_multiple(cb) {
+function test_up_multiple(realpath, realpathSync, cb) {
   console.error('test_up_multiple');
   if (skipSymlinks) {
     common.printSkipMessage('symlink test (no privs)');
-    return runNextTest();
-  }
-  function cleanup() {
-    ['a/b',
-     'a'
-    ].forEach(function(folder) {
-      try { fs.rmdirSync(tmp(folder)); } catch (ex) {}
-    });
+    return cb();
   }
-  function setup() {
-    cleanup();
-  }
-  setup();
+  common.refreshTmpDir();
   fs.mkdirSync(tmp('a'), 0o755);
   fs.mkdirSync(tmp('a/b'), 0o755);
   fs.symlinkSync('..', tmp('a/d'), 'dir');
@@ -413,16 +405,15 @@ function test_up_multiple(cb) {
   const abedabeda = tmp('abedabeda'.split('').join('/'));
   const abedabeda_real = tmp('a');
 
-  assertEqualPath(fs.realpathSync(abedabeda), abedabeda_real);
-  assertEqualPath(fs.realpathSync(abedabed), abedabed_real);
-  fs.realpath(abedabeda, function(er, real) {
+  assertEqualPath(realpathSync(abedabeda), abedabeda_real);
+  assertEqualPath(realpathSync(abedabed), abedabed_real);
+  realpath(abedabeda, function(er, real) {
     assert.ifError(er);
     assertEqualPath(abedabeda_real, real);
-    fs.realpath(abedabed, function(er, real) {
+    realpath(abedabed, function(er, real) {
       assert.ifError(er);
       assertEqualPath(abedabed_real, real);
       cb();
-      cleanup();
     });
   });
 }
@@ -436,7 +427,7 @@ function test_up_multiple(cb) {
 //     |       `-- x.txt
 //     `-- link -> /tmp/node-test-realpath-abs-kids/a/b/
 // realpath(root+'/a/link/c/x.txt') ==> root+'/a/b/c/x.txt'
-function test_abs_with_kids(cb) {
+function test_abs_with_kids(realpath, realpathSync, cb) {
   console.log('test_abs_with_kids');
 
   // this one should still run, even if skipSymlinks is set,
@@ -476,16 +467,25 @@ function test_abs_with_kids(cb) {
   setup();
   const linkPath = `${root}/a/link/c/x.txt`;
   const expectPath = `${root}/a/b/c/x.txt`;
-  const actual = fs.realpathSync(linkPath);
+  const actual = realpathSync(linkPath);
   // console.log({link:linkPath,expect:expectPath,actual:actual},'sync');
   assertEqualPath(actual, path.resolve(expectPath));
-  asynctest(fs.realpath, [linkPath], cb, function(er, actual) {
+  asynctest(realpath, [linkPath], cb, function(er, actual) {
     // console.log({link:linkPath,expect:expectPath,actual:actual},'async');
     assertEqualPath(actual, path.resolve(expectPath));
     cleanup();
   });
 }
 
+function test_root(realpath, realpathSync, cb) {
+  assertEqualPath(root, realpathSync('/'));
+  realpath('/', function(err, result) {
+    assert.ifError(err);
+    assertEqualPath(root, result);
+    cb();
+  });
+}
+
 // ----------------------------------------------------------------------------
 
 const tests = [
@@ -500,8 +500,10 @@ const tests = [
   test_deep_symlink_mix,
   test_non_symlinks,
   test_escape_cwd,
+  test_upone_actual,
   test_abs_with_kids,
-  test_up_multiple
+  test_up_multiple,
+  test_root,
 ];
 const numtests = tests.length;
 let testsRun = 0;
@@ -512,17 +514,15 @@ function runNextTest(err) {
     return console.log(`${numtests} subtests completed OK for fs.realpath`);
   }
   testsRun++;
-  test(runNextTest);
+  test(fs.realpath, fs.realpathSync, common.mustCall((err) => {
+    assert.ifError(err);
+    testsRun++;
+    test(fs.realpath.native,
+         fs.realpathSync.native,
+         common.mustCall(runNextTest));
+  }));
 }
 
-
-assertEqualPath(root, fs.realpathSync('/'));
-fs.realpath('/', function(err, result) {
-  assert.ifError(err);
-  assertEqualPath(root, result);
-});
-
-
 function runTest() {
   const tmpDirs = ['cycles', 'cycles/folder'];
   tmpDirs.forEach(function(t) {
@@ -536,6 +536,6 @@ function runTest() {
 
 
 process.on('exit', function() {
-  assert.strictEqual(numtests, testsRun);
+  assert.strictEqual(2 * numtests, testsRun);
   assert.strictEqual(async_completed, async_expected);
 });