Improve Markdown extension error messages.

Fixes #782. Note that we mock Markdown in the tests to ensure those
tests are not using Markdown to validate the extension names. We don't
mock Markdown in the tests which we do want Markdown to validate the
extension names.

Also ensure project-min has all relevant extensions.

docs/about/release-notes.md

@@ -66,6 +66,7 @@ authors should review how [search and themes] interact.
 
 ### Other Changes and Additions to Development Version
 
+* Improve Markdown extension error messages. (#782).
 * Drop official support for Python 3.3 and set `tornado>=5.0` (#1427).
 * Add support for GitLab edit links (#1435).
 * Link to GitHub issues from release notes (#644).

mkdocs/config/config_options.py

@@ -3,6 +3,7 @@ from __future__ import unicode_literals
 from collections import Sequence
 import os
 from collections import namedtuple
+import markdown
 
 from mkdocs import utils, theme, plugins
 from mkdocs.config.base import Config, ValidationError
@@ -629,7 +630,16 @@ class MarkdownExtensions(OptionallyRequired):
                 extensions.append(item)
             else:
                 raise ValidationError('Invalid Markdown Extensions configuration')
-        return utils.reduce_list(self.builtins + extensions)
+
+        extensions = utils.reduce_list(self.builtins + extensions)
+
+        # Confirm that Markdown considers extensions to be valid
+        try:
+            markdown.Markdown(extensions=extensions, extension_configs=self.configdata)
+        except Exception as e:
+            raise ValidationError(e.args[0])
+
+        return extensions
 
     def post_validation(self, config, key_name):
         config[self.configkey] = self.configdata

mkdocs/tests/config/config_options_tests.py

@@ -2,6 +2,7 @@ from __future__ import unicode_literals
 
 import os
 import unittest
+from mock import patch
 
 import mkdocs
 from mkdocs import utils
@@ -491,7 +492,8 @@ class PrivateTest(unittest.TestCase):
 
 class MarkdownExtensionsTest(unittest.TestCase):
 
-    def test_simple_list(self):
+    @patch('markdown.Markdown')
+    def test_simple_list(self, mockMd):
         option = config_options.MarkdownExtensions()
         config = {
             'markdown_extensions': ['foo', 'bar']
@@ -503,7 +505,8 @@ class MarkdownExtensionsTest(unittest.TestCase):
             'mdx_configs': {}
         }, config)
 
-    def test_list_dicts(self):
+    @patch('markdown.Markdown')
+    def test_list_dicts(self, mockMd):
         option = config_options.MarkdownExtensions()
         config = {
             'markdown_extensions': [
@@ -522,7 +525,8 @@ class MarkdownExtensionsTest(unittest.TestCase):
             }
         }, config)
 
-    def test_mixed_list(self):
+    @patch('markdown.Markdown')
+    def test_mixed_list(self, mockMd):
         option = config_options.MarkdownExtensions()
         config = {
             'markdown_extensions': [
@@ -539,7 +543,8 @@ class MarkdownExtensionsTest(unittest.TestCase):
             }
         }, config)
 
-    def test_builtins(self):
+    @patch('markdown.Markdown')
+    def test_builtins(self, mockMd):
         option = config_options.MarkdownExtensions(builtins=['meta', 'toc'])
         config = {
             'markdown_extensions': ['foo', 'bar']
@@ -577,7 +582,8 @@ class MarkdownExtensionsTest(unittest.TestCase):
             'mdx_configs': {'toc': {'permalink': True}}
         }, config)
 
-    def test_configkey(self):
+    @patch('markdown.Markdown')
+    def test_configkey(self, mockMd):
         option = config_options.MarkdownExtensions(configkey='bar')
         config = {
             'markdown_extensions': [
@@ -605,12 +611,14 @@ class MarkdownExtensionsTest(unittest.TestCase):
             'mdx_configs': {}
         }, config)
 
-    def test_not_list(self):
+    @patch('markdown.Markdown')
+    def test_not_list(self, mockMd):
         option = config_options.MarkdownExtensions()
         self.assertRaises(config_options.ValidationError,
                           option.validate, 'not a list')
 
-    def test_invalid_config_option(self):
+    @patch('markdown.Markdown')
+    def test_invalid_config_option(self, mockMd):
         option = config_options.MarkdownExtensions()
         config = {
             'markdown_extensions': [
@@ -622,7 +630,8 @@ class MarkdownExtensionsTest(unittest.TestCase):
             option.validate, config['markdown_extensions']
         )
 
-    def test_invalid_config_item(self):
+    @patch('markdown.Markdown')
+    def test_invalid_config_item(self, mockMd):
         option = config_options.MarkdownExtensions()
         config = {
             'markdown_extensions': [
@@ -634,7 +643,8 @@ class MarkdownExtensionsTest(unittest.TestCase):
             option.validate, config['markdown_extensions']
         )
 
-    def test_invalid_dict_item(self):
+    @patch('markdown.Markdown')
+    def test_invalid_dict_item(self, mockMd):
         option = config_options.MarkdownExtensions()
         config = {
             'markdown_extensions': [
@@ -645,3 +655,13 @@ class MarkdownExtensionsTest(unittest.TestCase):
             config_options.ValidationError,
             option.validate, config['markdown_extensions']
         )
+
+    def test_unknown_extension(self):
+        option = config_options.MarkdownExtensions()
+        config = {
+            'markdown_extensions': ['unknown']
+        }
+        self.assertRaises(
+            config_options.ValidationError,
+            option.validate, config['markdown_extensions']
+        )

requirements/project-min.txt

@@ -4,3 +4,4 @@ livereload==2.5.1
 Markdown==2.5
 PyYAML==3.10
 tornado==4.1
+mdx_gh_links>=0.2