Support --force-color for runserver

[Zach Waggoner]

Currently, the --force-color option doesn't work for the runserver management command. In my own experimentation, I was able to force color output by changing self.style = color_style() to self.style = color_style(force_color=True) in django.utils.log.ServerFormatter. I can of course achieve this by using my own django.server formatter class, but it would be convenient to have it built in.

[Mariusz Felisiak]

It already works properly, you just need to set the DJANGO_COLORS environment variable to reach ServerFormatter, see ​docs.

[Zach Waggoner]

Replying to felixxm:

It already works properly, you just need to set the DJANGO_COLORS environment variable to reach ServerFormatter, see ​docs.

I might be missing something, but that doesn't work for me. As an example, trying to run this Procfile through ​honcho does not preserve the color output:

web: DJANGO_COLORS=dark python manage.py runserver

and neither does:

web: DJANGO_COLORS=dark python manage.py runserver --force-color

This is on Django 3.1.

[Mariusz Felisiak]

It looks that Django doesn't recognize that your system's terminal supports color, we have an open ticket to improve detection on Windows, see #31216. You may also fake the installation of ANSICON by setting the appropriate environmental variable, ANSICON="on". Please use one of support channels.

[Zach Waggoner]

Replying to felixxm:

It looks that Django doesn't recognize that your system's terminal supports color, we have an open ticket to improve detection on Windows, see #31216. You may also fake the installation of ANSICON by setting the appropriate environmental variable, ANSICON="on". Please use one of support channels.

I'm on macOS, but I already expect that Django would not recognize that the execution context supports color because it is being run in a non-TTY context (through honcho). The point of --force-color is to bypass the color support detection altogether and output colors anyway. Running runserver directly (not within honcho) does output colors. Furthermore, running a different management command like migrate with the --force-color option within honcho preserves the color output, as expected. Therefore the problem is specific to runserver.

I glanced through the source code, and it looks like django.core.management.base.BaseCommand handles the --force-color option by setting self.style = color_style(force_color). Then the specific commands which inherit from BaseCommand, like migrate, use self.style when writing to stdout. However, runserver, while inheriting from BaseCommand, doesn't ever reference self.style, nor does it do anything else with --force-color. Instead, the style object is defined in django.utils.log.ServerFormatter as self.style = color_style(), so force_color is never True regardless of any environment variables. That is why I said in my original comment that the current way to solve this is to override ServerFormatter, but it seems like Django could support --force-color for runserver, perhaps by setting an environment variable that is picked up by the default ServerFormatter? Or if there are reasons not to do this, then perhaps the documentation should be updated to note that runserver does not support --force-color.