fix: strip colors when stdout is not a TTY

src/git_commit_guard/__init__.py

@@ -85,14 +85,28 @@ class Level(StrEnum):
     ERROR = "error"
     WARN = "warn"
     INFO = "info"
+    OK = "ok"
 
 
 PREFIXES = {
-    Level.ERROR: "\033[31m✗\033[0m",
-    Level.WARN: "\033[33m⚠\033[0m",
-    Level.INFO: "\033[34mi\033[0m",
+    Level.ERROR: "✗",
+    Level.WARN: "⚠",
+    Level.INFO: "i",
+    Level.OK: "✓",
 }
 
+COLORS = {
+    Level.ERROR: "31",
+    Level.WARN: "33",
+    Level.INFO: "34",
+    Level.OK: "32",
+}
+
+
+def _prefix(level, *, color=True):
+    sym = PREFIXES[level]
+    return f"\033[{COLORS[level]}m{sym}\033[0m" if color else sym
+
 
 @dataclass
 class Result:
@@ -504,12 +518,13 @@ def _report_jsonl(result, sha, subject):
 
 
 def _report_text(result):
+    color = sys.stdout.isatty()
     for check, level, msg in result.errors:
         prefix = f"[{check}] " if check else ""
-        print(f"  {PREFIXES[level]} {prefix}{msg}")
+        print(f"  {_prefix(level, color=color)} {prefix}{msg}")
 
     if result.ok:
-        print("  \033[32m✓\033[0m all checks passed")
+        print(f"  {_prefix(Level.OK, color=color)} all checks passed")
 
     return 0 if result.ok else 1
 

tests/test_git_commit_guard.py

@@ -638,6 +638,26 @@ def test_with_warning_returns_zero(self, capsys):
         assert "heads up" in captured
         assert "all checks passed" in captured
 
+    def test_no_ansi_when_not_tty(self, capsys):
+        r = Result()
+        r.error("something broke")
+        with patch("sys.stdout.isatty", return_value=False):
+            _report_text(r)
+        assert "\033[" not in capsys.readouterr().out
+
+    def test_ansi_when_tty(self, capsys):
+        r = Result()
+        r.error("something broke")
+        with patch("sys.stdout.isatty", return_value=True):
+            _report_text(r)
+        assert "\033[" in capsys.readouterr().out
+
+    def test_ok_no_ansi_when_not_tty(self, capsys):
+        r = Result()
+        with patch("sys.stdout.isatty", return_value=False):
+            _report_text(r)
+        assert "\033[" not in capsys.readouterr().out
+
 
 class TestReportJsonl:
     def test_ok_commit(self, capsys):