Disable coloring with TERM=dumb or NO_COLOR (#2541)

* Disable coloring with TERM=dumb or NO_COLOR

Fixes: #1290

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

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Add changelog fragment

* Fixed logic

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

Author: ssbarnea

docs/changelog/1290.bugfix.rst

@@ -0,0 +1 @@
+Recognize ``TERM=dumb`` or ``NO_COLOR`` environment variables. - by :user:`ssbarnea`.

src/tox/config/cli/parser.py

@@ -292,14 +292,16 @@ def add_color_flags(parser: ArgumentParser) -> None:
         color = "no"
     elif converter.to_bool(os.environ.get("FORCE_COLOR", "")):
         color = "yes"
+    elif os.environ.get("TERM", "") == "dumb":
+        color = "no"
     else:
         color = "yes" if sys.stdout.isatty() else "no"
 
     parser.add_argument(
         "--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

@@ -31,15 +31,22 @@ 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, "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:
@@ -53,6 +60,8 @@ def test_parser_color(
         expected = False
     elif force_color == "1":
         expected = True
+    elif term == "dumb":
+        expected = False
     else:
         expected = is_atty