Fix fs.realpath to return on error

[bpasero]

There is a missing return statement on error for fs.realpath.

[bnoordhuis]

Patch LGTM. Can you sign the CLA?

Sanity check: what does test/simple/test-fs-realpath.js with the below patch applied do with and without your patch?

diff --git a/test/simple/test-fs-realpath.js b/test/simple/test-fs-realpath.js
index 27ac0b8..b2c8e9b 100644
--- a/test/simple/test-fs-realpath.js
+++ b/test/simple/test-fs-realpath.js
@@ -79,6 +79,19 @@ function bashRealpath(path, callback) {
 }

 // sub-tests:
+function test_simple_error_callback() {
+  var ncalls = 0;
+
+  fs.realpath('/this/path/does/not/exist', function(err, s) {
+    assert(err);
+    assert(!s);
+    ncalls++;
+  });
+
+  process.on('exit', function() {
+    assert.equal(ncalls, 1);
+  });
+}

 function test_simple_relative_symlink(callback) {
   console.log('test_simple_relative_symlink');
@@ -415,6 +428,7 @@ function test_lying_cache_liar(cb) {
 // ----------------------------------------------------------------------------

 var tests = [
+  test_simple_error_callback,
   test_simple_relative_symlink,
   test_simple_absolute_symlink,
   test_deep_relative_file_symlink,

@piscisaureus: Can you confirm the issue?

[bpasero]

I signed the CLA electronically. I hope its fine, otherwise let me know. Thanks.

[bpasero]

Your test shows that the callback is being called twice, it demonstrates the issue if my patch is not applied (ncalls will be 2 in that case).

[bnoordhuis]

Thanks, Benjamin. Merged in b1bb17f.

[bpasero]

That was quick, thanks!