Set coloured output with a context manager

[chrisjsewell]

Rather than having singular nocolor and coloron functions (left for back-compatibility, introduce a colorize_output context manager, for temporarily enabling / disabling colorized output streams, on entering, then return to the initial state on exit.

Two outstandung questions:

1. double-check working of colorama init/deinit (see https://github.com/tartley/colorama/blob/master/colorama/initialise.py#L23)
2. currently make_app is now set to always have color deactivated (which helps for checking output strings), but maybe this should be configurable?

[jayaddison]

Based on the docstring: should there be toggle actions both before and after the yield statement?

Suggested change

	if on:
	coloron()
	else:
	nocolor()
	yield
	(coloron if on else nocolor)()
	yield
	(nocolor if on else coloron)()

...or something neater (example for illustration purposes, not necessarily good code).

[chrisjsewell]

maybe toggle is the wrong word then; it should just turn on/off colorization, on entering the context, then return it to the initial state on exiting the context

[jayaddison]

I'm a little wary of thread-safety / potential timing issues related to the codes object, but thanks for resolving my concern about the content of this function. The code as you have it is OK with me 👍

[chrisjsewell]

Oh I'm not a fan of any mutable global variables, I wish there wasn't so many in docutils/sphinx 😅

[picnixz]

Hadn't looked at it yet but you might need to fix the ColorizeFormatter of the logging module as well. That was what I wanted to fix yesterday so that the environment variable is handled properly in loggers.

[picnixz]

Didn't see your questions, sorry.

currently make_app is now set to always have color deactivated (which helps for checking output strings), but maybe this should be configurable?

This can be configured I think by changing the environment variable by using NO_COLOR or FORCE_COLOR. However, as I've said in #12089, you need to patch the logger formatter so that it knows whether to add colors or not.

[chrisjsewell]

Hadn't looked at it yet but you might need to fix the ColorizeFormatter of the logging module as well

this looks ok to me, basically it ends up calling:

sphinx/sphinx/util/console.py

Line 88 in 3f3d3d8

escape = codes.get(name, '')

and codes will be empty if nocolor is set

[chrisjsewell]

This can be configured I think by changing the environment variable by using NO_COLOR or FORCE_COLOR

I don't believe this to be the case for testing; these variables are only evaluated in sphinx.util.console.color_terminal, which is called as part of build_main (i.e. for the CLI), but nowhere in the the testing fixtures