Disable coloring with TERM=dumb or NO_COLOR

Fixes: tox-dev#1290

Related: https://no-color.org/

src/tox/config/cli/parser.py

@@ -290,6 +290,8 @@ def add_color_flags(parser: ArgumentParser) -> None:
     converter = StrConvert()
     if converter.to_bool(os.environ.get("NO_COLOR", "")):
         color = "no"
+    elif os.environ.get("TERM", "") == "dumb":
+        color = "no"
     elif converter.to_bool(os.environ.get("FORCE_COLOR", "")):
         color = "yes"
     else:
@@ -299,7 +301,7 @@ def add_color_flags(parser: ArgumentParser) -> None:
         "--colored",
         default=color,
         choices=["yes", "no"],
-        help="should output be enriched with colors",
+        help="should output be enriched with colors, default is yes unless TERM=dumb or NO_COLOR is defined.",
     )
 
 

tests/config/cli/test_parser.py

@@ -31,23 +31,27 @@ def test_parser_const_with_default_none(monkeypatch: MonkeyPatch) -> None:
 @pytest.mark.parametrize("no_color", [None, "0", "1"])
 @pytest.mark.parametrize("force_color", [None, "0", "1"])
 @pytest.mark.parametrize("tox_color", [None, "bad", "no", "yes"])
+@pytest.mark.parametrize("term", [None, None, "xterm", "dumb"])
 def test_parser_color(
     monkeypatch: MonkeyPatch,
     mocker: MockerFixture,
     no_color: str | None,
     force_color: str | None,
     tox_color: str | None,
     is_atty: bool,
+    term: str | None,
 ) -> None:
-    for key, value in {"NO_COLOR": no_color, "TOX_COLORED": tox_color, "FORCE_COLOR": force_color}.items():
+    for key, value in {"NO_COLOR": no_color, "TOX_COLORED": tox_color, "FORCE_COLOR": force_color, "TERM": term}.items():
         if value is None:
             monkeypatch.delenv(key, raising=False)
         else:
             monkeypatch.setenv(key, value)
     stdout_mock = mocker.patch("tox.config.cli.parser.sys.stdout")
     stdout_mock.isatty.return_value = is_atty
 
-    if tox_color in ("yes", "no"):
+    if term == 'dumb':
+        expected = False
+    elif tox_color in ("yes", "no"):
         expected = tox_color == "yes"
     elif no_color == "1":
         expected = False