thewoolleyman/process_helper

Support color in terminals

Closed this issue · 6 comments

oppegard commented

When using the ruby system method to shell out, it sets the correct options to preserve color in the output. For example system(rspec --color). ProcessHelper should do the same.

Looking at the RSpec code, it uses the #tty? method to determine if color is supported, which is usually IO#tty? on $stdout.

In this specific instance, RSpec can be forced to use color by adding the --tty option in addition to --color; since ProcessHelper is intended for use on any command, it's best to support color output rather than figure out one-off overrides for every command.

thewoolleyman commented

Do you have any idea what the fix should be to support color output?

thewoolleyman commented

I believe this bug is specific to Rspec, because it attempts to detect if it is running in a tty, and if not it will not output color.

Basic printing of color works fine, and I've added some tests to prove it in the latest commit.

I might be able to add an option to use a Pseudo TTY, but I'm not sure if this would work in all cases, since capturing output doesn't behave like a TTY in all aspects, and also not sure if it's compatible with Open3#popen2e, which is the crux of how ProcessHelper works.

thewoolleyman commented

As you said this rspec issue describes this situation exactly, and you can force rspec to color even on non-tty by adding --tty.

So, I'm not sure why Kernel#system reports as a tty while Open3#popen2e does not, or if it is overrideable by a Pseudo TTY or other means.

oppegard commented

I think the crux of the issue is making processes think they're in a TTY. This is how they detect whether or not to use color in their output. Primary examples of losing color are the bosh and cf CLIs.

oppegard commented

You might look at https://github.com/stripe/subprocess. I tried the following and it outputs color:

$ gem install subproccess
$ ruby -rsubprocess -e "Subprocess.check_call(['cf', 'apps'])"
# ...(it fails because I'm not authenticated to CF)...
$ echo $?
1

It also works for the BOSH CLI: ruby -rsubprocess -e "Subprocess.check_call(['bosh', 'status'])".

thewoolleyman commented

As of 9cadff1, color now works if you invoke the command in a pseudo terminal via the pseudo_terminal: true (pty: true) option.