Allow any characters in filenames / labels

[damienmg]

Ultimately any character can be part of a filename. We should probably allow that.

Some mangling to generate the corresponding label should probably be done.

Original report on the mailing-list:
https://groups.google.com/d/msgid/bazel-discuss/CAN0GiO3__5jXo5rZqroSj0mFxpqCzUZZVkY%3DSNsJK1%2BZ1BdJLg%40mail.gmail.com

[abergmeier]

1. So are we talking Unicode?
2. Where does any character stop?
3. how do you treat characters that are not allowed on certain platforms?
4. When using mangling, how do you handle collisions?

[kayasoze]

In POSIX, filenames are "bags of bytes"--there is no encoding; however, NUL and / are not allowed. Windows has a few more restrictions. Perhaps the BUILD file should be parsed in the encoding of the system locale, usually UTF-8, and filenames run though a ValidForCurrentPlatform() function which checks for disallowed characters. However, opting for strict platform neutrality in this way means that Bazel would have to represent filenames as a bag of bytes and not a Unicode string, as there is no guarantee that the filename will roundtrip through Unicode correctly. The problem can probably be simplified by restricting filenames to be UTF-8 or UTF-16, which should cover most people's needs even though that's not strict POSIX.

[ulfjack]

Well, I think we can probably require valid UTF-8 file names and strongly recommend that people use UTF-8 for their file system. For labels / BUILD files, we probably need an escaping scheme, at least for the control characters. If there's a file that isn't valid UTF-8, we give an error message?

[btelles]

Our company codes mainly in C++, but our frontend uses a lot of JS and nodejs modules which have all sorts of characters in the filenames--for example, -, #, @, (, and ).

Right now this is a major blocker for getting all our codebase under one build system since we can't reference files with semi-special characters. I don't think Bazel should decide what characters are acceptable in file names, as that reduces file names to those that fit both (1) supported languages and (2) supported platforms. This seems unnecessarily restrictive, and is becoming a major pain point for us.

[ulfjack]

Agreed. Unfortunately, it's a bit tricky to fix, as a lot of code assumes that the mapping from labels to file names (and vice versa) is trivial, and doesn't require escaping. Any suggestions on an escaping scheme?

[damienmg]

URL based?

[abergmeier]

You mean an own URI scheme? Sounds good.

[damienmg]

I mean replacing special characters by %XX where XX is the UTF-8 code in hexa.

[ulfjack]

Sorry, I won't be able to work on this. @philwo had an interest, maybe he can make some progress here. :-/

[kayasoze]

This blocks our Bazel deployment as well.

[RonnieAtOracle]

This is blocking us. We have a templating system where we need to build our template files. The filenames themselves contains template variables (e.g. ${ServiceName}.java ). Both $, {, and } are not supported by Bazel in file names.

[philwo]

I totally agree that this is important, should be done, I want this myself, however I don't have the time to work on it in the coming months, thus I have to unassign it.

[DemiMarie]

Here is my proposal:

• Metacharacters (:, %, =, any others) must be %-encoded
• All other characters are allowed. This includes Unicode characters.
• Non-UTF8 names are not allowed, even if escaped. This is because there is no good way to handle them cross-platform, nor to display them to the user.

[mihnita]

Plain ASCII (and even that partial) makes this feels like we are in the early 90s.

There are reasonable ways to handle that.
For POSIX using the default locale would be good enough.

If my project is C/C++, and it is cross-platform, and I have problems handling Unicode, then I will not use Unicode in file names. And the fact that bazel "explodes" is not such a problem.
But if I use something like Java, then "it just works", and bazel would work too.

Even better would be to to allow for a character-set option in the project file.
This is what maven does. And what Java does with -Dfile.encoding=UTF-8
So if it is there, use it. If not, then take the system charset.

I did not move one project to bazel because test units check that Unicode file names work.
So the files are there, make it through git, work with maven and ant and gradle and java.
But bazel fails because there is an "@" in the file name... Which is supported on all OSes.

[phst]

Thanks!
What about the runfiles manifest on Windows? It can't be UTF-16 (that would be the appropriate OS encoding, but not ASCII-compatible), so is it UTF-8 even on Windows?

[phst]

Starlark and other Bazel files (e.g. .bazelrc, manifests, ...) are assumed (but not enforced) to be encoded in UTF-8

Stardoc assumes Latin-1 for docstrings, though. Encoding a Starlark file in UTF-8 will result in double-encoding, cf. https://github.com/phst/rules_elisp/blob/master/docs/generate.py#L236-L239

[phst]

If Starlark files are now asssumed to be UTF-8, then I guess for Stardoc https://github.com/bazelbuild/bazel/blob/8.0.0/src/main/java/com/google/devtools/build/lib/starlarkdocextract/RuleInfoExtractor.java#L65 and similar occurrences (basically wherever a string proto field in the Stardoc proto is set) need to be fixed

[fmeum]

Thanks! What about the runfiles manifest on Windows? It can't be UTF-16 (that would be the appropriate OS encoding, but not ASCII-compatible), so is it UTF-8 even on Windows?

Yes, all output files produced by Bazel should use UTF-8 and \n line endings on all platforms, including Windows.

If Starlark files are now asssumed to be UTF-8, then I guess for Stardoc https://github.com/bazelbuild/bazel/blob/8.0.0/src/main/java/com/google/devtools/build/lib/starlarkdocextract/RuleInfoExtractor.java#L65 and similar occurrences (basically wherever a string proto field in the Stardoc proto is set) need to be fixed

Thanks for pointing that out, I sent #24935 to fix this.

[phst]

I wasn't aware of that docs statement, I will update it.

Here's another doc that I guess is outdated now: https://bazel.build/concepts/labels

• Repository names: No documentation, but I'd assume that even with this change repository names (both canonical and apparent) are ASCII-only, with some more restrictions (no newlines, spaces, slashes, ...)
• Package names: Since package names correspond to directory names, these can now also contain non-ASCII characters?
• Target names: Definitely can contain non-ASCII characters now.

[phst]

Yes, all output files produced by Bazel should use UTF-8 and \n line endings on all platforms, including Windows.

OK, then the runfiles libraries also need to be adapted.

• Go: Probably no change needed, Go uses WTF-8 for filenames on Windows
• Python: Probably only need to make sure that files are opened with the correct encoding (fix: Fix encoding of runfiles manifest and repository mapping files. rules_python#2568)
• C++: A lot more changes required. The use of narrow strings throughout makes manifest files and directories with non-ASCII characters nonportable/impossible. We need at least overloads for Create and Rlocation with std::wstring on Windows.
• Others: ???

[fmeum]

Thanks for sending the fix for Python!

C++: A lot more changes required. The use of narrow strings throughout makes manifest files and directories with non-ASCII characters nonportable/impossible. We need at least overloads for Create and Rlocation with std::wstring on Windows.

Microsoft now recommends using the -A variety of functions with the UTF-8 code page (forced via an app manifest) instead of the wide string functions for new software. Existing software probably already has its own conversion functions to and from UTF-8, so I would personally lean against complicating the API for everyone by adding more overloads.