Allow new versions to replace existing aliases when `--update-aliases…

…` is set

README.md

@@ -120,9 +120,11 @@ mike deploy [version] [alias]...
 If `[version]` already exists, this command will *also* update all of the
 pre-existing aliases for it. Normally, if an alias specified on the command line
 is already associated with another version, this will return an error. If you
-*do* want to move an alias from another version to this version (e.g. when
+*do* want to move an alias from another version to this version (including
+when the new version itself was previously an alias), you can pass
+`-u`/`--update-aliases` to allow this. For example, this can be useful when
 releasing a new version and updating the `latest` alias to point to this new
-version), you can pass `-u`/`--update-aliases` to allow this.
+version.
 
 By default, each alias creates a symbolic link to the base directory of the real
 version of the docs; to create a copy of the docs for each alias, you can pass

mike/versions.py

@@ -137,6 +137,15 @@ def find(self, identifier, strict=False):
 
     def _ensure_unique_aliases(self, version, aliases, update_aliases=False):
         removed_aliases = []
+
+        # Check whether `version` is already defined as an alias.
+        key = self.find(version)
+        if key and len(key) == 2:
+            if not update_aliases:
+                raise ValueError('version {!r} already exists'.format(version))
+            removed_aliases.append(key)
+
+        # Check whether any `aliases` are already defined.
         for i in aliases:
             key = self.find(i)
             if key and key[0] != version:
@@ -150,6 +159,7 @@ def _ensure_unique_aliases(self, version, aliases, update_aliases=False):
                         .format(i, str(key[0]))
                     )
                 removed_aliases.append(key)
+
         return removed_aliases
 
     def add(self, version, title=None, aliases=[], update_aliases=False):
@@ -161,8 +171,6 @@ def add(self, version, title=None, aliases=[], update_aliases=False):
         if v in self._data:
             self._data[v].update(title, aliases)
         else:
-            if self.find(version):
-                raise ValueError('version {!r} already exists'.format(version))
             self._data[v] = VersionInfo(version, title, aliases)
 
         # Remove aliases from old versions that we've moved to this version.

test/integration/test_deploy.py

@@ -132,6 +132,15 @@ def test_update_aliases(self):
             versions.VersionInfo('1.0'),
         ])
 
+    def test_update_aliases_with_version(self):
+        assertPopen(['mike', 'deploy', '1.0b1', '1.0'])
+        assertPopen(['mike', 'deploy', '1.0', 'latest', '-u'])
+        check_call_silent(['git', 'checkout', 'gh-pages'])
+        self._test_deploy(expected_versions=[
+            versions.VersionInfo('1.0', aliases=['latest']),
+            versions.VersionInfo('1.0b1'),
+        ])
+
     def test_from_subdir(self):
         os.mkdir('sub')
         with pushd('sub'):

test/unit/test_versions.py

@@ -354,11 +354,15 @@ def test_add_overwrite_version_with_alias(self):
     def test_add_overwrite_alias_with_version(self):
         versions = Versions()
         versions.add('1.0b1', aliases=['1.0'])
+
         msg = r"version '1\.0' already exists"
         with self.assertRaisesRegex(ValueError, msg):
             versions.add('1.0')
-        with self.assertRaisesRegex(ValueError, msg):
-            versions.add('1.0', update_aliases=True)
+        versions.add('1.0', update_aliases=True)
+        self.assertEqual(list(versions), [
+            VersionInfo('1.0'),
+            VersionInfo('1.0b1'),
+        ])
 
     def test_add_invalid(self):
         versions = Versions()