Quick fix for incremental rc version normalization.

src/towncrier/_project.py

@@ -13,7 +13,7 @@
 from importlib import import_module
 from types import ModuleType
 
-from incremental import Version
+from incremental import Version as IncrementalVersion
 
 
 def _get_package(package_dir: str, package: str) -> ModuleType:
@@ -50,8 +50,12 @@ def get_version(package_dir: str, package: str) -> str:
     if isinstance(version, str):
         return version.strip()
 
-    if isinstance(version, Version):
-        return version.base().strip()
+    if isinstance(version, IncrementalVersion):
+        # FIXME:https://github.com/twisted/incremental/issues/81
+        # Incremental uses `.rcN`.
+        # importlib uses `rcN` (without a dot separation).
+        # Here we make incremental work like importlib.
+        return version.base().strip().replace(".rc", "rc")
 
     if isinstance(version, tuple):
         return ".".join(map(str, version)).strip()
@@ -76,7 +80,7 @@ def get_project_name(package_dir: str, package: str) -> str:
     if isinstance(version, str):
         return package.title()
 
-    if isinstance(version, Version):
+    if isinstance(version, IncrementalVersion):
         # Incremental has support for package names
         return version.package
 

src/towncrier/test/test_project.py

@@ -14,9 +14,9 @@
 
 
 try:
-    from importlib.metadata import version
+    from importlib.metadata import version as metadata_version
 except ImportError:
-    version = None
+    metadata_version = None
 
 
 class VersionFetchingTests(TestCase):
@@ -48,14 +48,14 @@ def test_tuple(self):
         version = get_version(temp, "mytestproja")
         self.assertEqual(version, "1.3.12")
 
-    @skipIf(version is None, "Needs importlib.metadata.")
+    @skipIf(metadata_version is None, "Needs importlib.metadata.")
     def test_incremental(self):
         """
         An incremental Version __version__  is picked up.
         """
         pkg = "../src"
 
-        self.assertEqual(version("towncrier"), get_version(pkg, "towncrier"))
+        self.assertEqual(metadata_version("towncrier"), get_version(pkg, "towncrier"))
         self.assertEqual("towncrier", get_project_name(pkg, "towncrier"))
 
     def _setup_missing(self):