fix: detect color support for xterm-* TERM values (xterm-color, xterm-kitty)

progressbar/env.py

@@ -45,9 +45,12 @@ def from_env(cls) -> ColorSupport:
         """Get the color support from the environment.
 
         If any of the environment variables contain `24bit` or `truecolor`,
-        we will enable true color/24 bit support. If they contain `256`, we
-        will enable 256 color/8 bit support. If they contain `xterm`, we will
-        enable 16 color support. Otherwise, we will assume no color support.
+        we will enable true color/24 bit support. A `TERM` that is itself a
+        truecolor terminal (see `TRUECOLOR_TERMS`) also enables 24 bit
+        support. If they contain `256`, we will enable 256 color/8 bit
+        support. If they match a known ANSI terminal (see `ANSI_TERM_RE`,
+        e.g. `xterm-color`, `screen`, `tmux`, `konsole`, `rxvt`, `linux`), we
+        will enable 16 color support. Otherwise, we assume no color support.
 
         If `JUPYTER_COLUMNS` or `JUPYTER_LINES` or `JPY_PARENT_PID` is set, we
         will assume true color support.
@@ -115,9 +118,15 @@ def _from_term_variables(
                 # Truecolor support, we don't need to check anything else.
                 support = cls.XTERM_TRUECOLOR
                 break
+            elif value in TRUECOLOR_TERMS:
+                # A TERM name that itself guarantees a 24-bit terminal.
+                support = max(cls.XTERM_TRUECOLOR, support)
             elif '256' in value:
                 support = max(cls.XTERM_256, support)
-            elif value == 'xterm':
+            elif ANSI_TERM_RE.match(value):
+                # Any recognized ANSI terminal (xterm-color, screen, tmux,
+                # konsole, rxvt, linux, ...) advertises at least 16 colors,
+                # matching is_ansi_terminal()'s use of the same pattern.
                 support = max(cls.XTERM, support)
             elif env_flag(variable, default=False):
                 return cls.XTERM_TRUECOLOR
@@ -200,7 +209,6 @@ def is_terminal(
     or os.environ.get('JUPYTER_LINES')
     or os.environ.get('JPY_PARENT_PID')
 )
-COLOR_SUPPORT = ColorSupport.from_env()
 ANSI_TERMS = (
     '([xe]|bv)term',
     '(sco)?ansi',
@@ -215,3 +223,12 @@ def is_terminal(
 ANSI_TERM_RE: re.Pattern[str] = re.compile(
     f'^({"|".join(ANSI_TERMS)})', re.IGNORECASE
 )
+
+#: TERM values that on their own guarantee a truecolor-capable terminal, so
+#: 24-bit color still engages when ``COLORTERM`` is stripped (e.g. over ssh
+#: or sudo). Limited to names that *are* the terminal; generic values such as
+#: ``xterm-256color`` are used by plenty of 256-only emulators.
+TRUECOLOR_TERMS: frozenset[str] = frozenset({'xterm-kitty', 'xterm-ghostty'})
+
+# Defined after ANSI_TERM_RE / TRUECOLOR_TERMS because from_env() reads them.
+COLOR_SUPPORT = ColorSupport.from_env()

tests/test_color.py

@@ -96,6 +96,42 @@ def test_color_support_from_env(monkeypatch, variable, value) -> None:
     env.ColorSupport.from_env()
 
 
+@pytest.mark.parametrize(
+    ('term', 'expected'),
+    [
+        # Bare ``xterm`` and any ``xterm-*`` variant advertise (at least) 16
+        # color support, matching the documented "if they contain ``xterm``"
+        # behaviour and ``is_ansi_terminal``'s ``^xterm`` prefix match.
+        ('xterm', env.ColorSupport.XTERM),
+        ('xterm-color', env.ColorSupport.XTERM),
+        ('xterm-16color', env.ColorSupport.XTERM),
+        # Every other ANSI_TERM_RE terminal is 16-color too, not NONE.
+        ('screen', env.ColorSupport.XTERM),
+        ('tmux', env.ColorSupport.XTERM),
+        ('konsole', env.ColorSupport.XTERM),
+        ('rxvt-unicode', env.ColorSupport.XTERM),
+        ('linux', env.ColorSupport.XTERM),
+        # A ``256`` anywhere in the value still wins over plain xterm.
+        ('xterm-256color', env.ColorSupport.XTERM_256),
+        ('screen-256color', env.ColorSupport.XTERM_256),
+        # TERM names that are themselves truecolor terminals engage 24-bit
+        # color even when COLORTERM is stripped (ssh, sudo).
+        ('xterm-kitty', env.ColorSupport.XTERM_TRUECOLOR),
+        ('xterm-ghostty', env.ColorSupport.XTERM_TRUECOLOR),
+        # Unknown terminals still mean no detected support.
+        ('dumb', env.ColorSupport.NONE),
+    ],
+)
+def test_color_support_from_env_term(monkeypatch, term, expected) -> None:
+    if os.name == 'nt':
+        # Windows has special handling so we need to disable that to make the
+        # tests work properly
+        monkeypatch.setattr(os, 'name', 'posix')
+
+    monkeypatch.setenv('TERM', term)
+    assert env.ColorSupport.from_env() == expected
+
+
 @pytest.mark.parametrize(
     'variable',
     [