fix: fall back for legacy-encoded spinners

Author: nightcityblade

nox/_parallel.py

@@ -67,6 +67,7 @@
     from nox.sessions import SessionRunner
 
 _SPINNER = "⠋⠙⠹⠸⠼⠴⠦⠧⠇⠏"
+_ASCII_SPINNER = "|/-\\"
 _SYMBOLS = {
     Status.SUCCESS: "✓",
     Status.SKIPPED: "⊘",
@@ -129,6 +130,15 @@ def _status_symbol(status: Status, encoding: str | None) -> str:
     return symbol
 
 
+def _spinner_frame(spin: int, encoding: str | None) -> str:
+    frame = _SPINNER[spin % len(_SPINNER)]
+    try:
+        frame.encode(encoding or "utf-8")
+    except UnicodeEncodeError:
+        return _ASCII_SPINNER[spin % len(_ASCII_SPINNER)]
+    return frame
+
+
 @dataclasses.dataclass(kw_only=True)
 class _Reporter:
     """Buffers per-session output and renders progress.
@@ -206,7 +216,7 @@ def _render(self, now: float, width: int) -> list[str]:
             header = plain_header[: width - 1]
         lines = [self._banner(width), header]
 
-        frame = _SPINNER[self._spin % len(_SPINNER)]
+        frame = _spinner_frame(self._spin, self.stream.encoding)
         for name, start in self._active.items():
             # Plain and colored renderings are built from the same segments so
             # the width math can't drift from what is actually displayed.

tests/test_parallel.py

@@ -613,6 +613,15 @@ def test_reporter_render_truncates_to_width() -> None:
     assert "\x1b" not in line
 
 
+def test_reporter_render_uses_ascii_spinner_for_legacy_encoding() -> None:
+    buffer = io.BytesIO()
+    with io.TextIOWrapper(buffer, encoding="cp1252") as stream:
+        reporter = _parallel._Reporter(color=False, tty=True, total=1)
+        reporter.stream = stream
+        reporter._active = {"a": 100.0}
+        assert reporter._render(105.0, width=0)[2] == "| a (5s)"
+
+
 def test_reporter_render_color() -> None:
     reporter = _parallel._Reporter(color=True, tty=False, total=1)
     reporter._active = {"a": 100.0}