ENOENT thrown when trying to create a file with an invalid filename

[Daniel15]

Node v6.7.0, Windows 10

To reproduce the issue:

fs.writeFileSync('C:\\temp\\foo:bar:baz', 'fail')

Expected output: Some error message about the filename being invalid because it contains colons

Actual output:

Error: ENOENT: no such file or directory, open 'C:\temp\foo:bar:baz'
    at Error (native)
    at Object.fs.openSync (fs.js:640:18)
    at Object.fs.writeFileSync (fs.js:1333:33)
    at repl:1:4
    at sigintHandlersWrap (vm.js:22:35)
    at sigintHandlersWrap (vm.js:96:12)
    at ContextifyScript.Script.runInThisContext (vm.js:21:12)
    at REPLServer.defaultEval (repl.js:313:29)
    at bound (domain.js:280:14)
    at REPLServer.runBound [as eval] (domain.js:293:12)

[silverwind]

Pretty sure that error codes comes straight from the Windows API, and it even seems consistent with macOS, so I'd lean towards leaving it as-is. Doing a check for filename validity on Windows is costly and should probably be done by the user.

[Daniel15]

Pretty sure that error codes comes straight from the Windows API

Are you sure? I tried the equivalent in C#:

File.WriteAllText("c:\\temp\\foo:bar:baz", "winning");

And got a better error message:

System.NotSupportedException: The given path's format is not supported.

Or:

System.ArgumentException: Illegal characters in path.

I didn't try raw Win32 API calls though.

[addaleax]

So, just in case this is helpful: Colons are used by NTFS to name separate Alternate Data Streams, so if there’s a file named foo, creating foo:bar and writing to it (as an ADS) should work.

So it would seem to me that ENOENT would be the correct code for writing to foo:bar when foo doesn’t exist.

I’m not sure the overhead of checking for multiple colons would be worth it…

[mscdex]

I believe it might be technically possible to provide a better error message since CreateFileW() on Windows probably sets the 'last error' code to ERROR_BAD_PATHNAME in such cases. From what I can tell, the original Windows-specific error code is stored by libuv in such a way that node should have access to it.

[Daniel15]

So it would seem to me that ENOENT would be the correct code for writing to foo:bar when foo doesn’t exist.

Interesting, I didn't know that.

The same error message happens for other invalid characters though, such as question marks:

> fs.writeFileSync('C:\\temp\\foo??', 'fail')
Error: ENOENT: no such file or directory, open 'C:\temp\foo??'
    at Error (native)
    at Object.fs.openSync (fs.js:640:18)
    at Object.fs.writeFileSync (fs.js:1333:33)
    at repl:1:4

[seishun]

The issue here is that libuv maps ERROR_INVALID_NAME to UV_ENOENT here. This particular mapping was added by @piscisaureus way back in 2012.

The question is what it should map to instead. Would UV_EINVAL be better? Understandably, libuv doesn't have a dedicated error code for an invalid file name since Linux doesn't have invalid filenames.

[piscisaureus]

You could change it (major version), but before you do so, do some research into what different "libc" implementations do on windows - at least try what error the open() call in msvcrt produces when you try to create a file with an invalid name, and try cygwin too.