Only install and import colorama on Windows.

[hwalinga]

Related: #612

Only install and import colorama on Windows. Importing and init call has no effect on other platforms, so no need to do it on other platforms.

• I have added an entry to docs/changelog.md

Summary of changes

Just check if on Windows, do import and call init. Also, colorama dep is now listed as a windows specific dep.

Test plan

Tested by running:

pipx list --verbose

[itsayellow]

Does this have a measurable benefit? (Startup time, etc.)

[hwalinga]

Barely anything significant. But that is not the reason I took the effort to submit this PR.

To give some background. I use poetry as my dependency manager and poetry will always uninstall colorama because pylint and pytest both list colorama as a Windows only dependency. Breaking pipx every time I use poetry.

You can say this is a poetry bug, or that I just have to install pipx in its own environment, pipx install pipx is what I have now ; ). But listing colorama as a Windows only dependency is just more correct, just as pylint and pytest have done, and just makes sure pipx is a bit more robust on other platforms if there goes anything wrong with colorama.

[itsayellow]

Ah ok, I didn't realize there was this side effect with poetry. Your motivation makes more sense now.

It's too bad, because the whole point of colorama is that it works cross-platform and you don't have to conditionally install on Windows. 😕

[hwalinga]

Yes, that is true, if other tools didn't specify colorama as Windows only and just ran it unconditionally Poetry would never decided to remove it. It's just that Python dependency management isn't as robust as it can be. Without that problem pipx might have never existed.

Here is the issue from Poetry talking about that:
python-poetry/poetry#3139

[jimxliu]

Hello! I came across the following error when I was trying to poetry lock pipx 1.0.0 with colorama 0.4.3 on linux (ubuntu). As stated in this PR, >= 0.4.4 is only required in windows.

  SolverProblemError

  Because pipx (1.0.0) depends on colorama (>=0.4.4)
   and my-app depends on colorama (0.4.3), pipx is forbidden.
  So, because my-app depends on pipx (1.0.0), version solving failed.

And the pyproject.toml looks like this

[tool.poetry.dependencies]
colorama = "0.4.3"
python = "^3.7"
typer = "^=0.4.0"
pipx = "1.0.0"
virtualenv = "^20.8.1"
joblib = "^1.1.0"

system python 3.7

Any thoughts on why it didn't follow the linux requirement? Thank you!

[jimxliu]

I figured out a solution by adding { version = "*", markers = "sys_platform == 'linux'" } to pipx. Thanks