🐛 fix(spec): compare version specifiers at their written precision

docs/changelog/+spec-specifier-precision.bugfix.rst

@@ -0,0 +1,2 @@
+``PythonSpec.satisfies`` now checks a version specifier at the precision it was written with, so ``3.11`` no longer
+satisfies ``>=3.13``. This also lets the Windows registry pre-filter skip interpreters that can't match.

src/python_discovery/_py_spec.py

@@ -2,7 +2,6 @@
 
 from __future__ import annotations
 
-import contextlib
 import pathlib
 import re
 from typing import Final
@@ -235,27 +234,25 @@ def _check_version_specifier(self, spec: PythonSpec) -> bool:
         if not components:
             return True
 
-        version_str = ".".join(str(part) for part in components)
         if spec.version_specifier is None:
             return True
-        with contextlib.suppress(InvalidVersion):
-            Version.from_string(version_str)
-            for item in spec.version_specifier:
-                required_precision = self._get_required_precision(item)
-                if required_precision is None or len(components) < required_precision:
-                    continue
-                if not item.contains(version_str):
-                    return False
+        for item in spec.version_specifier:
+            required_precision = self._get_required_precision(item)
+            if required_precision is None or len(components) < required_precision:
+                continue
+            # compare at the precision the specifier was written with, as PythonInfo.satisfies does
+            if not item.contains(".".join(str(part) for part in components[:required_precision])):
+                return False
         return True
 
     @staticmethod
     def _get_required_precision(item: SimpleSpecifier) -> int | None:
-        """Get the required precision for a specifier item."""
+        """Get the number of release parts a specifier item was written with (``>=3.12`` has two)."""
         if item.version is None:
             return None
-        with contextlib.suppress(AttributeError, ValueError):
-            return len(item.version.release)
-        return None
+        if item.wildcard_precision is not None:
+            return item.wildcard_precision
+        return re.split(r"a|b|rc", item.version_str, maxsplit=1)[0].count(".") + 1
 
     def satisfies(self, spec: PythonSpec) -> bool:  # ruff:ignore[too-many-return-statements]
         """

tests/test_py_spec_extra.py

@@ -1,7 +1,5 @@
 from __future__ import annotations
 
-from unittest.mock import MagicMock
-
 import pytest
 
 from python_discovery import PythonSpec
@@ -165,16 +163,35 @@ def test_specifier_set_parsed_for_valid_format() -> None:
     assert spec.implementation == "cpython"
 
 
-def test_get_required_precision_attribute_error() -> None:
+@pytest.mark.parametrize(
+    ("text", "expected"),
+    [
+        pytest.param(">=3", 1, id="major"),
+        pytest.param(">=3.12", 2, id="minor"),
+        pytest.param(">=3.12.1", 3, id="micro"),
+        pytest.param(">=3.14rc1", 2, id="minor-pre"),
+        pytest.param(">=3.14.0b2", 3, id="micro-pre"),
+        pytest.param("==3.12.*", 2, id="wildcard"),
+    ],
+)
+def test_get_required_precision_counts_written_parts(text: str, expected: int) -> None:
     from python_discovery._specifier import SimpleSpecifier
 
-    mock_version = MagicMock(spec=[])
-    specifier = SimpleSpecifier(
-        spec_str=">=3.12",
-        operator=">=",
-        version_str="3.12",
-        is_wildcard=False,
-        wildcard_precision=None,
-        version=mock_version,
-    )
-    assert PythonSpec._get_required_precision(specifier) is None
+    assert PythonSpec._get_required_precision(SimpleSpecifier.from_string(text)) == expected
+
+
+@pytest.mark.parametrize(
+    ("candidate", "text", "expected"),
+    [
+        pytest.param("3.11", ">=3.13", False, id="minor-too-old"),
+        pytest.param("3.14", "<3.13", False, id="minor-too-new"),
+        pytest.param("3.11", "==3.12.*", False, id="minor-wildcard-miss"),
+        pytest.param("3.12", "==3.12.*", True, id="minor-wildcard-hit"),
+        pytest.param("3.13", ">=3.12,<3.14", True, id="minor-in-range"),
+        pytest.param("3", ">=4", False, id="major-too-old"),
+        pytest.param("3.12", ">=3.12.5", True, id="micro-unknown"),
+        pytest.param("3.12.1", "==3.12", True, id="micro-at-minor-precision"),
+    ],
+)
+def test_version_specifier_compared_at_written_precision(candidate: str, text: str, expected: bool) -> None:
+    assert PythonSpec.from_string_spec(candidate).satisfies(PythonSpec.from_string_spec(text)) is expected