Improve error handling with theme discovery

mkdocs/tests/utils_tests.py

@@ -4,7 +4,9 @@
 import os
 import unittest
 
-from mkdocs import nav, utils
+import mock
+
+from mkdocs import nav, utils, exceptions
 
 
 class UtilsTests(unittest.TestCase):
@@ -112,6 +114,44 @@ def test_get_themes(self):
                     'spacelab', 'united', 'readable', 'simplex', 'mkdocs',
                     'cosmo', 'journal', 'cyborg', 'readthedocs', 'amelia']))
 
+    @mock.patch('pkg_resources.iter_entry_points', autospec=True)
+    def test_get_themes_warning(self, mock_iter):
+
+        theme1 = mock.Mock()
+        theme1.name = 'mkdocs2'
+        theme1.dist.key = 'mkdocs2'
+        theme1.load().__file__ = "some/path1"
+
+        theme2 = mock.Mock()
+        theme2.name = 'mkdocs2'
+        theme2.dist.key = 'mkdocs3'
+        theme2.load().__file__ = "some/path2"
+
+        mock_iter.return_value = iter([theme1, theme2])
+
+        self.assertEqual(
+            sorted(utils.get_theme_names()),
+            sorted(['mkdocs2', ]))
+
+    @mock.patch('pkg_resources.iter_entry_points', autospec=True)
+    @mock.patch('pkg_resources.get_entry_map', autospec=True)
+    def test_get_themes_error(self, mock_get, mock_iter):
+
+        theme1 = mock.Mock()
+        theme1.name = 'mkdocs'
+        theme1.dist.key = 'mkdocs'
+        theme1.load().__file__ = "some/path1"
+
+        theme2 = mock.Mock()
+        theme2.name = 'mkdocs'
+        theme2.dist.key = 'mkdocs2'
+        theme2.load().__file__ = "some/path2"
+
+        mock_iter.return_value = iter([theme1, theme2])
+        mock_get.return_value = {'mkdocs': theme1, }
+
+        self.assertRaises(exceptions.ConfigurationError, utils.get_theme_names)
+
     def test_nest_paths(self):
 
         j = os.path.join

mkdocs/utils.py

@@ -7,14 +7,17 @@
 and structure of the site and pages in the site.
 """
 
-from pkg_resources import iter_entry_points
+import logging
 import os
+import pkg_resources
 import shutil
 
 import markdown
 import six
 
-from mkdocs import toc
+from mkdocs import toc, exceptions
+
+log = logging.getLogger(__name__)
 
 
 def reduce_list(data_set):
@@ -289,12 +292,25 @@ def get_themes():
     """Return a dict of theme names and their locations"""
 
     themes = {}
+    builtins = pkg_resources.get_entry_map(dist='mkdocs', group='mkdocs.themes')
+
+    for theme in pkg_resources.iter_entry_points(group='mkdocs.themes'):
+
+        if theme.name in builtins and theme.dist.key != 'mkdocs':
+            raise exceptions.ConfigurationError(
+                "The theme {0} is a builtin theme but {1} provides a theme "
+                "with the same name".format(theme.name, theme.dist.key))
+
+        elif theme.name in themes:
+            multiple_packages = [themes[theme.name].dist.key, theme.dist.key]
+            log.warning("The theme %s is provided by the Python package "
+                        "'%s'. The one in %s will be used.",
+                        theme.name, ','.join(multiple_packages), theme.dist.key)
+
+        themes[theme.name] = theme
 
-    for theme in iter_entry_points(group='mkdocs.themes', name=None):
-        name = theme.name
-        theme = theme.load()
-        location = os.path.dirname(theme.__file__)
-        themes[name] = location
+    themes = dict((name, os.path.dirname(theme.load().__file__))
+                  for name, theme in themes.items())
 
     return themes