First step towards pypa#524

src/setuptools_scm/__init__.py

@@ -157,6 +157,7 @@ def get_version(
     parse=None,
     git_describe_command=None,
     dist_name=None,
+    version_cls=None,  # or name it version_factory ?
 ):
     """
     If supplied, relative_to should be a file from which root may

src/setuptools_scm/config.py

@@ -66,6 +66,7 @@ def __init__(
         parse=None,
         git_describe_command=None,
         dist_name=None,
+        version_cls=None,
     ):
         # TODO:
         self._relative_to = relative_to
@@ -83,6 +84,7 @@ def __init__(
         self.tag_regex = tag_regex
         self.git_describe_command = git_describe_command
         self.dist_name = dist_name
+        self.version_cls = version_cls
 
     @property
     def fallback_root(self):

src/setuptools_scm/version.py

@@ -98,7 +98,11 @@ def tag_to_version(tag, config=None):
             )
         )
 
-    if VERSION_CLASS is not None:
+    # use custom version class if provided
+    if config.version_cls is not None:
+        version = config.version_cls(version)
+        trace("version", repr(version))
+    elif VERSION_CLASS is not None:
         version = pkg_parse_version(version)
         trace("version", repr(version))
 
@@ -187,7 +191,9 @@ def format_next_version(self, guess_next, fmt="{guessed}.dev{distance}", **kw):
 def _parse_tag(tag, preformatted, config):
     if preformatted:
         return tag
-    if VERSION_CLASS is None or not isinstance(tag, VERSION_CLASS):
+    # use custom version class if provided
+    version_cls = config.version_cls or VERSION_CLASS
+    if version_cls is None or not isinstance(tag, version_cls):
         tag = tag_to_version(tag, config)
     return tag
 

testing/test_basic_api.py

@@ -123,3 +123,17 @@ def parse(root):
 
     with pytest.raises(TypeError):
         setuptools_scm.get_version(parse=parse)
+
+
+# def test_custom_version_cls(monkeypatch):
+#
+#     monkeypatch.setenv(setuptools_scm.PRETEND_KEY, "1.0.1")
+#
+#     class MyVersion:
+#         def __init__(self, tag_str: str):
+#             # todo
+#             pass
+#
+#     # TODO unfortunately with PRETEND_KEY the preformatted flag becomes True which bypasses our class.
+#     #   which other mechanism would be ok to use ?
+#     assert setuptools_scm.get_version(version_cls=MyVersion) == "1"

testing/test_version.py

@@ -170,3 +170,19 @@ def test_version_bump_bad():
     ):
 
         guess_next_version(tag_version="2.0.0-alpha.5-PMC")
+
+
+def test_custom_version_cls():
+    """Test that we can pass our own version class instead of pkg_resources"""
+
+    class MyVersion:
+        def __init__(self, tag_str: str):
+            self.tag = tag_str
+
+        def __repr__(self):
+            return "Custom %s" % self.tag
+
+    scm_version = meta("1.0.0-foo", config=Configuration(version_cls=MyVersion))
+
+    assert isinstance(scm_version.tag, MyVersion)
+    assert repr(scm_version.tag) == "Custom 1.0.0-foo"