Update noxutil.py

Add `python` parameter to `get_version()` allowing one to limit versions based on the python version.

noxutil.py

@@ -2,7 +2,7 @@
 
 from collections.abc import Iterable
 from pathlib import Path
-from typing import Optional
+from typing import Union
 from urllib.request import urlopen, Request
 
 from poetry.core.factory import Factory
@@ -15,16 +15,20 @@
 VERSION_PARTS = ('major', 'minor', 'patch')
 
 
-def get_versions(dependency: str, granularity: str = 'minor',
-                 # ascending: bool = False, limit: Optional[int] = None,
-                 # allow_prerelease: bool = False,
-                 ) -> Iterable[str]:
+def get_versions(
+    dependency: str,
+    granularity: str = "minor",
+    python: Union[str, None] = None,
+    # ascending: bool = False, limit: Optional[int] = None,
+    # allow_prerelease: bool = False,
+) -> Iterable[str]:
     """Yield all versions of `dependency` considering version constraints
 
     Args:
         dependency: the name of the dependency
         granularity: yield only the newest patch version of each major/minor
             release
+        python: version of python or None
         ascending: count backwards from latest version, by default (not much
             use without the 'limit' arg)
         limit: maximum number of entries to return
@@ -36,16 +40,33 @@ def get_versions(dependency: str, granularity: str = 'minor',
 
     """
     package = Factory().create_poetry(Path(__file__).parent).package
-    for requirement in package.requires:
-        if requirement.name == dependency:
-            break
-    else:
+    requirements = [
+        requirement
+        for requirement in package.requires
+        if requirement.name == dependency
+    ]
+    if not requirements:
         raise ValueError(f"{package.name} has no dependency '{dependency}'")
-    filtered_versions = [version for version in all_versions(dependency)
-                         if requirement.constraint.allows(version)]
-    parts = VERSION_PARTS[:VERSION_PARTS.index(granularity) + 1]
+
+    def allowed(version):
+        """Return True if the version is allowed."""
+        if python is None:
+            return any(
+                requirement.constraint.allows(version) for requirement in requirements
+            )
+
+        python_version = parse_single_constraint(python)
+        for requirement in requirements:
+            python_versions = parse_single_constraint(requirement.python_versions)
+            if python_versions.allows(python_version) and requirement.constraint.allows(
+                version
+            ):
+                return True
+        return False
+
+    parts = VERSION_PARTS[: VERSION_PARTS.index(granularity) + 1]
     result = {}
-    for version in filtered_versions:
+    for version in filter(allowed, all_versions(dependency)):
         key = tuple(getattr(version, part) for part in parts)
         result[key] = (max((result[key], version))
                        if key in result else version)