Fix canonicalize_version to accept Version instances (#328)

* Fix `canonicalize_version` to accept Version instances

* Update utils.py

* Update test_utils.py

packaging/utils.py

@@ -23,18 +23,18 @@ def canonicalize_name(name):
     return cast("NormalizedName", value)
 
 
-def canonicalize_version(_version):
-    # type: (str) -> Union[Version, str]
+def canonicalize_version(version):
+    # type: (Union[Version, str]) -> Union[Version, str]
     """
     This is very similar to Version.__str__, but has one subtle difference
     with the way it handles the release segment.
     """
-
-    try:
-        version = Version(_version)
-    except InvalidVersion:
-        # Legacy versions cannot be normalized
-        return _version
+    if not isinstance(version, Version):
+        try:
+            version = Version(version)
+        except InvalidVersion:
+            # Legacy versions cannot be normalized
+            return version
 
     parts = []
 

tests/test_utils.py

@@ -6,6 +6,7 @@
 import pytest
 
 from packaging.utils import canonicalize_name, canonicalize_version
+from packaging.version import Version
 
 
 @pytest.mark.parametrize(
@@ -30,6 +31,7 @@ def test_canonicalize_name(name, expected):
 @pytest.mark.parametrize(
     ("version", "expected"),
     [
+        (Version("1.4.0"), "1.4"),
         ("1.4.0", "1.4"),
         ("1.40.0", "1.40"),
         ("1.4.0.0.00.000.0000", "1.4"),