fix: reject NaN/Inf --wait so the CLI cannot hang

src/whoseport/__init__.py

@@ -5,7 +5,10 @@
 """
 
 from whoseport.core import PortUser, UnsupportedPlatformError, collect
+from whoseport.waitarg import install as _install_waitarg
 
 __version__ = "0.2.0"
 
+_install_waitarg()
+
 __all__ = ["PortUser", "UnsupportedPlatformError", "__version__", "collect"]

src/whoseport/waitarg.py

@@ -0,0 +1,42 @@
+"""Guards for ``--wait`` so a typo cannot hang the CLI forever."""
+
+from __future__ import annotations
+
+import math
+
+
+def require_finite_wait(seconds: float) -> float:
+    """Return *seconds* if it is a finite, positive duration.
+
+    ``argparse`` ``type=float`` accepts ``nan`` / ``inf``. ``nan <= 0`` is
+    false, so the old ``<= 0`` check let ``--wait nan`` through and
+    ``--wait inf`` never hit the timeout.
+    """
+    value = float(seconds)
+    if not math.isfinite(value) or value <= 0:
+        raise ValueError("--wait needs a positive number of seconds")
+    return value
+
+
+def _wait_type(text: str) -> float:
+    return require_finite_wait(float(text))
+
+
+def install() -> None:
+    """Patch ``cli.build_parser`` so ``--wait`` rejects NaN/Inf."""
+    import whoseport.cli as cli
+
+    if getattr(cli, "_waitarg_installed", False):
+        return
+
+    orig = cli.build_parser
+
+    def build_parser():
+        parser = orig()
+        for action in parser._actions:
+            if "--wait" in getattr(action, "option_strings", ()):
+                action.type = _wait_type
+        return parser
+
+    cli.build_parser = build_parser
+    cli._waitarg_installed = True

tests/test_wait_finite.py

@@ -0,0 +1,41 @@
+import math
+
+import pytest
+
+from whoseport import cli
+from whoseport.waitarg import require_finite_wait
+
+
+def test_require_finite_wait_accepts_positive():
+    assert require_finite_wait(0.5) == 0.5
+    assert require_finite_wait(30) == 30
+
+
+def test_require_finite_wait_rejects_non_positive_and_non_finite():
+    for bad in (0, -1, float("nan"), float("inf"), float("-inf")):
+        with pytest.raises(ValueError, match="positive"):
+            require_finite_wait(bad)
+
+
+def test_cli_wait_rejects_nan():
+    with pytest.raises(SystemExit) as exc:
+        cli.main(["8080", "--wait", "nan"])
+    assert exc.value.code == 2
+
+
+def test_cli_wait_rejects_inf():
+    with pytest.raises(SystemExit) as exc:
+        cli.main(["8080", "--wait", "inf"])
+    assert exc.value.code == 2
+
+
+def test_cli_wait_rejects_negative_inf():
+    with pytest.raises(SystemExit) as exc:
+        cli.main(["8080", "--wait", "-inf"])
+    assert exc.value.code == 2
+
+
+def test_math_nan_is_not_less_or_equal_zero():
+    # documents why the old `<= 0` guard was not enough
+    assert not (float("nan") <= 0)
+    assert math.isnan(float("nan"))