MkDocs: allow None on extra_css/extra_javascript (#8976)

Currently we are failing the build if we find None values,
but MkDocs allows them.

Author: stsewd

readthedocs/doc_builder/backends/mkdocs.py

@@ -4,9 +4,9 @@
 .. _MkDocs: http://www.mkdocs.org/
 """
 
-import structlog
 import os
 
+import structlog
 import yaml
 from django.conf import settings
 from django.template import loader as template_loader
@@ -149,35 +149,35 @@ def append_conf(self):
 
         # Set mkdocs config values
         static_url = get_absolute_static_url()
+        extra_assets = {
+            'extra_javascript': [
+                'readthedocs-data.js',
+                f'{static_url}core/js/readthedocs-doc-embed.js',
+                f'{static_url}javascript/readthedocs-analytics.js',
+            ],
+            'extra_css': [
+                f'{static_url}css/badge_only.css',
+                f'{static_url}css/readthedocs-doc-embed.css',
+            ],
+        }
 
-        for config in ('extra_css', 'extra_javascript'):
-            user_value = user_config.get(config, [])
-            if not isinstance(user_value, list):
+        for config, extras in extra_assets.items():
+            value = user_config.get(config, [])
+            if value is None:
+                value = []
+            if not isinstance(value, list):
                 raise MkDocsYAMLParseError(
                     MkDocsYAMLParseError.INVALID_EXTRA_CONFIG.format(
                         config=config,
                     ),
                 )
-
-        extra_javascript_list = [
-            'readthedocs-data.js',
-            '%score/js/readthedocs-doc-embed.js' % static_url,
-            '%sjavascript/readthedocs-analytics.js' % static_url,
-        ]
-        extra_css_list = [
-            '%scss/badge_only.css' % static_url,
-            '%scss/readthedocs-doc-embed.css' % static_url,
-        ]
-
-        # Only add static file if the files are not already in the list
-        user_config.setdefault('extra_javascript', []).extend(
-            [js for js in extra_javascript_list if js not in user_config.get(
-                'extra_javascript')]
-        )
-        user_config.setdefault('extra_css', []).extend(
-            [css for css in extra_css_list if css not in user_config.get(
-                'extra_css')]
-        )
+            # Add the static file only if isn't already in the list.
+            value.extend([
+                extra
+                for extra in extras
+                if extra not in value
+            ])
+            user_config[config] = value
 
         # The docs path is relative to the location
         # of the mkdocs configuration file.

readthedocs/rtd_tests/tests/test_doc_builder.py

@@ -566,7 +566,7 @@ def test_append_conf_existing_yaml_on_root_with_invalid_setting(self, checkout_p
         yaml_contents = [
             {'docs_dir': ['docs']},
             {'extra_css': 'a string here'},
-            {'extra_javascript': None},
+            {'extra_javascript': ''},
         ]
         for content in yaml_contents:
             yaml.safe_dump(
@@ -576,6 +576,50 @@ def test_append_conf_existing_yaml_on_root_with_invalid_setting(self, checkout_p
             with self.assertRaises(MkDocsYAMLParseError):
                 self.searchbuilder.append_conf()
 
+    @patch('readthedocs.doc_builder.base.BaseBuilder.run')
+    @patch('readthedocs.projects.models.Project.checkout_path')
+    def test_append_conf_and_none_values(self, checkout_path, run):
+        tmpdir = tempfile.mkdtemp()
+        os.mkdir(os.path.join(tmpdir, 'docs'))
+        yaml_file = os.path.join(tmpdir, 'mkdocs.yml')
+        checkout_path.return_value = tmpdir
+
+        python_env = Virtualenv(
+            version=self.version,
+            build_env=self.build_env,
+            config=None,
+        )
+        builder = MkdocsHTML(
+            build_env=self.build_env,
+            python_env=python_env,
+        )
+
+        yaml.safe_dump(
+            {
+                'extra_css': None,
+                'extra_javascript': None,
+            },
+            open(yaml_file, 'w'),
+        )
+        builder.append_conf()
+        config = yaml_load_safely(open(yaml_file))
+
+        self.assertEqual(
+            config['extra_css'],
+            [
+                'http://readthedocs.org/static/css/badge_only.css',
+                'http://readthedocs.org/static/css/readthedocs-doc-embed.css',
+            ],
+        )
+        self.assertEqual(
+            config['extra_javascript'],
+            [
+                'readthedocs-data.js',
+                'http://readthedocs.org/static/core/js/readthedocs-doc-embed.js',
+                'http://readthedocs.org/static/javascript/readthedocs-analytics.js',
+            ],
+        )
+
     @patch('readthedocs.doc_builder.base.BaseBuilder.run')
     @patch('readthedocs.projects.models.Project.checkout_path')
     def test_dont_override_theme(self, checkout_path, run):