Fix is_valid_version() for prerelease versions

By default, the check if an empty specifier contains a prerelease
version returns `false`. This made the `is_valid_version()` check for
prerelease versions fail, when there is also a requirement with a
non-empty specifier. In this case, the previous logic detected a
conflict of the prerelease version and the empty specifier.

Fix this by explicitly allowing prerelease versions when checking if a
specifier contains a version.

Note that the function that collects candidates for a dependency still
ignores prerelease versions if any release versions are available, as
required by the specs [1].

[1]: https://packaging.python.org/en/latest/specifications/version-specifiers/#handling-of-pre-releases

Signed-off-by: Martin Nonnenmacher <[email protected]>

Author: mnonnenmacher

src/python_inspector/resolution.py

@@ -172,7 +172,9 @@ def is_valid_version(
     """
     if parsed_version in bad_versions:
         return False
-    if any(parsed_version not in r.specifier for r in requirements[identifier]):
+    if any(
+        not r.specifier.contains(parsed_version, prereleases=True) for r in requirements[identifier]
+    ):
         if all(not r.specifier for r in requirements[identifier]):
             return True
         return False

tests/test_resolution.py

@@ -196,6 +196,14 @@ def test_is_valid_version_with_no_specifier_and_pre_release():
     assert is_valid_version(parsed_version, requirements, identifier, bad_versions)
 
 
+def test_is_valid_version_with_empty_and_non_empty_specifier_and_pre_release():
+    parsed_version = packvers.version.parse("1.0.0.dev1+01234abcd")
+    requirements = {"flask": [Requirement("flask"), Requirement("flask==1.0.0.dev1+01234abcd")]}
+    bad_versions = []
+    identifier = "flask"
+    assert is_valid_version(parsed_version, requirements, identifier, bad_versions)
+
+
 def test_get_requirements_from_dependencies():
     dependencies = [
         models.DependentPackage(