[rejected AI] support FORCE_COLOR, NO_COLOR, and PYTHON_COLORS environment variables

[taran-dev4u]

Description

Currently, Click only determines the default color preference by checking whether the output stream is a physical TTY (isatty(stream)). In CI/CD environments (GitHub Actions, GitLab CI, Jenkins) and automated build logs, output streams are pipes/files where isatty() is False, which strips color and ANSI styling unless color=True is explicitly passed.

Standards like NO_COLOR, FORCE_COLOR, and Python 3.13's standard PYTHON_COLORS allow users and build environments to control ANSI color output globally.

Changes

1. src/click/globals.py:
   • Extended resolve_color_default() to inspect NO_COLOR, FORCE_COLOR, and PYTHON_COLORS when no explicit color flag or ctx.color is configured:
     • NO_COLOR (non-empty) or PYTHON_COLORS="0" / FORCE_COLOR="0" -> returns False (disable color).
     • FORCE_COLOR (non-zero/true) or PYTHON_COLORS="1" -> returns True (enable color).
2. src/click/_compat.py:
   • Updated should_strip_ansi() to respect NO_COLOR, FORCE_COLOR, and PYTHON_COLORS when color is None.
3. src/click/testing.py:
   • Updated CliRunner.isolation()'s should_strip_ansi mock to evaluate environment variables during test runs.
4. tests/test_utils/test_echo.py:
   • Added test_echo_force_color testing FORCE_COLOR=1, FORCE_COLOR=true, FORCE_COLOR=0, PYTHON_COLORS=1, PYTHON_COLORS=0, and explicit color=False override on non-TTY streams.
   • Added test_echo_no_color testing NO_COLOR=1, NO_COLOR="", and explicit color=True override on TTY streams.
   • Added test_echo_runner_env_color testing CliRunner invocations with environment variables.

Closes #3022

[davidism]

https://palletsprojects.com/contributing/llm-ai