gh-140082: Forward colorizing from libregrtest to unittest

[cmaloney]

libregrtest redirects test output to a file as part of its operation. When unittest checks to see if it should colorize with isatty(sys.stdout) that returns False resulting in no colorizing of the unittest output.

Update libregrtest to set FORCE_COLOR=1 when redirecting test output so that unittest will do color printing.

• Issue: Colorize failing test results in python -m test -W #140082

[cmaloney]

I think this can be skip news as it's a strictly internal change / libregrtest isn't externally exposed

[vstinner]

Is this change also needed?

[cmaloney]

Yes for single-process mode coloring of unittest output because unittest gets given a io.StringIO as its stdout (on which isatty returns False). ./python -m test -W --single-process with a failing test output is uncolored without this, colored with it.

[cmaloney]

I've been pondering if this would be better done by setting os.environ['FORCE_COLOR'] inside libregrtest main (

cpython/Lib/test/libregrtest/main.py

Lines 755 to 779 in 1e1f435

	def main(self, tests: TestList | None = None) -> NoReturn:
	if self.want_add_python_opts:
	self._add_python_opts()
	self._init()
	if self.want_cleanup:
	cleanup_temp_dir(self.tmp_dir)
	sys.exit(0)
	if self.want_wait:
	input("Press any key to continue...")
	setup_test_dir(self.test_dir)
	selected, tests = self.find_tests(tests)
	exitcode = 0
	if self.want_list_tests:
	self.list_tests(selected)
	elif self.want_list_cases:
	list_cases(selected,
	match_tests=self.match_tests,
	test_dir=self.test_dir)
	else:
	exitcode = self.run_tests(selected, tests)

) rather than inside the the single and parallel code paths separately; that seems like it's covering too much code though

[vstinner]

Would it be possible to move these 2 lines in setup_tests()?

[vstinner]

You might add a NEWS entry in the Tests category.

[vstinner]

Would it be possible to move these 2 lines in setup_tests()?

[vstinner]

Suggested change

	# The subcommand is run with a temporary output which means it is not a tty
	# The subcommand is run with a temporary output which means it is not a TTY