add helper to compare collection versions with prerelease awareness

galactory/utilities.py

@@ -145,6 +145,14 @@ def discover_collections(repo, namespace=None, name=None, version=None, fast_det
             yield coldata
 
 
+def _latest_collection_version(reference_collection: dict, difference_collection: dict, *, property: str = "semver"):
+    """Returns the latest of two collections."""
+    if (reference_collection[property].prerelease is None) == (difference_collection[property].prerelease is None):
+        return max(reference_collection, difference_collection, key=lambda x: x[property])
+
+    return reference_collection if reference_collection[property].prerelease is None else difference_collection
+
+
 def collected_collections(repo, namespace=None, name=None, scheme=None):
     collections = {}
 

tests/unit/utilities/test_utilities.py

@@ -0,0 +1,38 @@
+# -*- coding: utf-8 -*-
+# (c) 2023 Brian Scholer (@briantist)
+
+import pytest
+from unittest import mock
+
+from datetime import datetime, timedelta
+from types import GeneratorType
+import semver
+
+from galactory.utilities import _latest_collection_version
+
+
+@pytest.mark.parametrize(["ref", "dif", "exp"], [
+    ("0.0.0-dev0", "0.0.0-dev1", "0.0.0-dev1"),
+    ("0.0.0", "0.0.0-dev1", "0.0.0"),
+    ("1.2.3", "1.2.4", "1.2.4"),
+    ("0.0.0-dev0", "0.0.0-dev1", "0.0.0-dev1"),
+    ("0.0.0", "99.99.99-dev1", "0.0.0"),
+])
+@pytest.mark.parametrize("prop", [None, "semver", "other"])
+def test_latest_collection_version(ref, dif, exp, prop):
+    reference = semver.VersionInfo.parse(ref)
+    difference = semver.VersionInfo.parse(dif)
+    expected = ref if exp == ref else dif
+
+    opprop = {}
+    if prop is None:
+        expprop = "semver"
+    else:
+        opprop["property"] = expprop = prop
+
+    # ensure we didn't mess up the test cases
+    assert expected in [reference, difference]
+
+    result = _latest_collection_version({expprop: reference}, {expprop: difference}, **opprop)
+
+    assert result[expprop] == expected