Support the NO_COLOR environment variable

CHANGES.rst

@@ -2,10 +2,11 @@ Changes
 =======
 
 
-1.2.2 (unreleased)
+1.3.0 (unreleased)
 ------------------
 
-- Nothing changed yet.
+- Support the NO_COLOR environment variable for disabling color autodetection
+  (see https://no-color.org/).
 
 
 1.2.1 (2022-10-28)

strace_process_tree.py

@@ -21,7 +21,7 @@
 from functools import partial
 
 
-__version__ = '1.2.2.dev0'
+__version__ = '1.3.0.dev0'
 __author__ = 'Marius Gedminas <marius@gedmin.as>'
 __url__ = "https://github.com/mgedmin/strace-process-tree"
 __licence__ = 'GPL v2 or v3'  # or ask me for MIT
@@ -71,7 +71,11 @@ def __init__(self, color=None, unicode=None):
 
     @classmethod
     def should_use_color(cls):
-        return cls.is_terminal() and cls.terminal_supports_color()
+        return (
+            cls.is_terminal()
+            and cls.terminal_supports_color()
+            and not cls.user_dislikes_color()
+        )
 
     @classmethod
     def is_terminal(cls):
@@ -81,6 +85,11 @@ def is_terminal(cls):
     def terminal_supports_color(cls):
         return (os.environ.get('TERM') or 'dumb') != 'dumb'
 
+    @classmethod
+    def user_dislikes_color(cls):
+        # https://no-color.org/
+        return bool(os.environ.get('NO_COLOR'))
+
     @classmethod
     def can_unicode(cls):
         return getattr(sys.stdout, 'encoding', None) == 'UTF-8'

tests.py

@@ -1,5 +1,4 @@
 # -*- coding: utf-8 -*-
-import os
 import sys
 
 import pytest
@@ -22,24 +21,47 @@ def test_Theme_is_terminal_yes_it_is(monkeypatch):
 
 
 def test_Theme_terminal_supports_color_no(monkeypatch):
-    monkeypatch.setitem(os.environ, 'TERM', 'dumb')
+    monkeypatch.setenv('TERM', 'dumb')
     assert not stp.Theme.terminal_supports_color()
 
 
 def test_Theme_terminal_supports_color_yes(monkeypatch):
-    monkeypatch.setitem(os.environ, 'TERM', 'xterm')
+    monkeypatch.setenv('TERM', 'xterm')
     assert stp.Theme.terminal_supports_color()
 
 
+def test_Theme_no_color_unset(monkeypatch):
+    monkeypatch.delenv('NO_COLOR', raising=False)
+    assert not stp.Theme.user_dislikes_color()
+
+
+def test_Theme_no_color_blank(monkeypatch):
+    monkeypatch.setenv('NO_COLOR', '')
+    assert not stp.Theme.user_dislikes_color()
+
+
+def test_Theme_no_color_nonblank(monkeypatch):
+    monkeypatch.setenv('NO_COLOR', 'please')
+    assert stp.Theme.user_dislikes_color()
+
+
 def test_Theme_autodetection_color_yes(monkeypatch):
     monkeypatch.setattr(sys, 'stdout', FakeStdout())
-    monkeypatch.setitem(os.environ, 'TERM', 'xterm')
+    monkeypatch.setenv('TERM', 'xterm')
+    monkeypatch.delenv('NO_COLOR', raising=False)
     assert isinstance(stp.Theme(), stp.AnsiTheme)
 
 
 def test_Theme_autodetection_color_no(monkeypatch):
     monkeypatch.setattr(sys, 'stdout', FakeStdout())
-    monkeypatch.setitem(os.environ, 'TERM', 'dumb')
+    monkeypatch.setenv('TERM', 'dumb')
+    assert isinstance(stp.Theme(), stp.PlainTheme)
+
+
+def test_Theme_autodetection_color_disabled(monkeypatch):
+    monkeypatch.setattr(sys, 'stdout', FakeStdout())
+    monkeypatch.setenv('TERM', 'xterm')
+    monkeypatch.setenv('NO_COLOR', '1')
     assert isinstance(stp.Theme(), stp.PlainTheme)