🐛 fix(discovery): match prerelease versions against major.minor specs

Python prerelease versions like 3.15.0a6 were incorrectly failing to match
version specifiers like >=3.15. This broke testing of prereleases in Fedora
and other environments that build libraries against alpha/beta Python versions.

The root cause was always comparing the full version string "3.15.0a6" against
the normalized specifier version "3.15.0". Since PEP 440 defines prereleases
as strictly less than final releases, this comparison failed even though the
intent of >=3.15 is to match any 3.15.x version including prereleases.

The fix matches the comparison precision to the specifier precision. For a
two-component specifier like >=3.15, we now compare "3.15" without prerelease
suffix, allowing prereleases to satisfy the constraint. Prerelease suffixes
are only included when the specifier itself contains a prerelease marker.

Fixes #45

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: gaborbernat

src/python_discovery/_py_info.py

@@ -469,12 +469,22 @@ def _satisfies_version_specifier(self, spec: PythonSpec) -> bool:
         if spec.version_specifier is None:  # pragma: no cover
             return True
         version_info = self.version_info
-        release = f"{version_info.major}.{version_info.minor}.{version_info.micro}"
-        if version_info.releaselevel != "final":
-            suffix = {"alpha": "a", "beta": "b", "candidate": "rc"}.get(version_info.releaselevel)
-            if suffix is not None:  # pragma: no branch # releaselevel is always alpha/beta/candidate here
+        for specifier in spec.version_specifier:
+            if specifier.version is None:
+                continue
+            release = ".".join(
+                str(c)
+                for c in [version_info.major, version_info.minor, version_info.micro][: len(specifier.version.release)]
+            )
+            if (
+                specifier.version.pre_type is not None
+                and version_info.releaselevel != "final"
+                and (suffix := {"alpha": "a", "beta": "b", "candidate": "rc"}.get(version_info.releaselevel))
+            ):
                 release = f"{release}{suffix}{version_info.serial}"
-        return spec.version_specifier.contains(release)
+            if not specifier.contains(release):
+                return False
+        return True
 
     _current_system = None
     _current = None

tests/test_py_info_extra.py

@@ -297,6 +297,13 @@ def test_satisfies_prerelease_candidate() -> None:
     assert info.satisfies(spec, impl_must_match=False) is True
 
 
+def test_satisfies_prerelease_with_major_minor_spec() -> None:
+    info = copy.deepcopy(CURRENT)
+    info.version_info = VersionInfo(3, 15, 0, "alpha", 6)
+    spec = PythonSpec.from_string_spec(">=3.15")
+    assert info.satisfies(spec, impl_must_match=False) is True
+
+
 def test_satisfies_path_not_abs_basename_match() -> None:
     info = copy.deepcopy(CURRENT)
     basename = Path(info.original_executable).stem