Color support on Windows: TerminalWriter (PY_COLORS), colorama (PYCHARM_HOSTED)

[eine]

While running several tests with tox on GitHub Actions environments, tox's output is not coloured by default (see actions/starter-workflows#114). Setting PY_COLORS: 1 (#1009) works for jobs running on GNU/Linux (ubuntu-latest). Unfortunately, it seems not to be effective on windows-latest.

• ubuntu-latest: https://github.com/1138-4EB/vunit/runs/326860648#step:5:29
• windows-latest: https://github.com/1138-4EB/vunit/runs/326860617#step:7:31

Note that, in those examples, the output of the commands executed by tox is coloured because --color=yes is explicitly passed to pytest through {posargs}.

[gaborbernat]

We'd happy to fix this if someone can investigate and come up with a PR for it.

[eine]

I'd be happy to investigate if I have any reference. Currently, PY_COLORS seems not to be found in this repository, except in the help: https://github.com/tox-dev/tox/search?q=PY_COLORS&type=Code

[eine]

Here is a minimal reproducer GitHub Actions workflow:

name: "tox"
on: [push]
jobs:
  tox:
    strategy:
      fail-fast: false
      max-parallel: 2
      matrix:
        os: [ ubuntu, windows ]
    runs-on: ${{ matrix.os }}-latest
    steps:
    - uses: actions/setup-python@v1
      with:
        python-version: 3.7
    - uses: actions/checkout@v1
    - run: pip3 install tox --progress-bar off
    - run: tox -e py37-test
    - run: tox -e py37-test
      env:
        PY_COLORS: 1

Output: https://github.com/1138-4EB/actions/runs/327196070

[eine]

Upon further investigation, it seems that tox does not explicitly handle colouring at all:

tox/src/tox/reporter.py

Lines 101 to 102 in 9ee972e

	def good(self, msg):
	self.logline_if(Verbosity.QUIET, "good", msg, green=True)

tox/src/tox/reporter.py

Lines 72 to 75 in 9ee972e

	def logline_if(self, level, of, msg, key=None, **kwargs):
	if self.verbosity >= level:
	message = str(msg) if key is None else "{}{}".format(key, msg)
	self.logline(of, message, **kwargs)

tox/src/tox/reporter.py

Lines 77 to 83 in 9ee972e

	def logline(self, of, msg, **opts):
	self.reported_lines.append((of, msg))
	timestamp = ""
	if REPORTER_TIMESTAMP_ON:
	timestamp = "{} ".format(datetime.now() - START)
	line_msg = "{}{}\n".format(timestamp, msg)
	self.tw.write(line_msg, **opts)

tox/src/tox/reporter.py

Line 38 in 9ee972e

self.tw = py.io.TerminalWriter()

Hence, PY_COLORS is handled by py.io.TerminalWriter(). This is mentioned in #163, but not in the help/docs. I'd suggest to please explain this explicitly (#1009). For example:

tox depends on py.io.TerminalWriter to handle colouring, which supports forcing the behaviour with environment variable PY_COLORS: 0 disable, 1 enable (default).

---

Looking at the source of TerminalWriter, the usage of PY_COLORS seems straightforward:

https://github.com/pytest-dev/py/blob/1e99d20f31ef511fc2f1a9e49ba970acad441d4e/py/_io/terminalwriter.py#L131-L138

This issue might be related to the fact that TerminalWriter seems to depend on colorama when on windows:

https://github.com/pytest-dev/py/blob/1e99d20f31ef511fc2f1a9e49ba970acad441d4e/py/_io/terminalwriter.py#L15-L24

Unfortunately, colorama is currently not installed as a dependency; users need to do it explicitly. Moreover, it seems to be used only when a tty is available:

https://github.com/pytest-dev/py/blob/1e99d20f31ef511fc2f1a9e49ba970acad441d4e/py/_io/terminalwriter.py#L157-L158

As a result, it might be a bug in TerminalWriter, as using colorama might need to be forced when PY_COLORS is set (similar to pytest-dev/py#224). Still:

• TerminalWriter has not been updated in 7 months and the CI tests are broken. It "is in maintenance mode and should not be used in new code". Instead of trying to push a fix, it might be more sensible to copy/fork terminalwriter.py only.
• colorama itself will not colour the output when a tty is not available. It needs to be forced with PYCHARM_HOSTED (How to enable colorama in Gitlab tty (and other online services that seem to support colors in terminal) tartley/colorama#214). It would make sense if colorama supported PY_COLORS too (ping @tartley @wiggin15); or if TerminalWriter supported FORCE_COLOR and NOCOLOR (Added FORCE_COLOR and NO_COLOR environment variables tartley/colorama#230).

---

An alternative solution to properly honouring PY_COLORS in both TerminalWriter and colorama, is to have tartley/colorama#226 tested and merged, and then use it in TerminalWriter too.

[gaborbernat]

Closed via #1471

[eine]

@gaborbernat, note that this was not closed automatically on purpose. #1471 is just a quick fix and it might seem to work, but I believe that this issue needs to remain open. Let me elaborate:

With the current version of TerminalWriter, ensuring that colorama is installed will avoid win32_and_ctypes being used. However, colorama is not actually used unless a tty is available (which is not the case in some CI services, such as GHA):

https://github.com/pytest-dev/py/blob/1e99d20f31ef511fc2f1a9e49ba970acad441d4e/py/_io/terminalwriter.py#L157-L158

Hence, the current master of tox generates Linux type coloring on Windows when no TTY is used. I guess that this might work on web frontend, on bash (MSYS2/MINGW) and probably on powershell; but it is likely to be broken on cmd.

This is an effort to bring TerminalWriter to tox's codebase and clean it up so that colorama is always used on Windows. Unfortunately, in this context PY_COLORS=1 alone is uneffective, because not being a tty colorama requires PYCHARM_HOSTED=1 to be set too. I tried to make tox set it automatically, but it seems not to work.

Hence, as commented above, I think that it would make sense if colorama supported PY_COLORS; or if TerminalWriter supported FORCE_COLOR and NOCOLOR (tartley/colorama#230). Any of those would allow a single envvar to be used while ensuring that colorama is allowed to handle any terminal on windows.

Anyway, I later found #1400. It seems that py is removed completely and colorama is directly used instead. I think that's a great decission and I'm looking forward to having it released. Nonetheless, I believe that this issue should remain open until it is merged or until any other of the solutions is applied.