Add a setting to configure skip common chunks behaviour globally

You can now specify a 'SKIP_COMMON_CHUNKS' setting globally for each
Webpack configuration. This will perform the same 'skip_common_chunks'
logic from the 'render_bundle' template tag without having to add
a parameter to every tag.

To maintain backwards compatibility we default to 'False' and allow
common chunks to be rendered to the HTML document as script tags. In the
future, it will be easy to change this default behaviour if desired.

I've added test coverage to ensure that the global setting can be
override by the existing template tag parameter and that we maintain
backwards compatibility.

Author: hyshka

README.md

@@ -111,6 +111,8 @@ The `STATS_FILE` parameter represents the output file produced by `webpack-bundl
 
 - `LOADER_CLASS` is the fully qualified name of a python class as a string that holds the custom webpack loader. This is where behavior can be customized as to how the stats file is loaded. Examples include loading the stats file from a database, cache, external url, etc. For convenience, `webpack_loader.loader.WebpackLoader` can be extended. The `load_assets` method is likely where custom behavior will be added. This should return the stats file as an object.
 
+- `SKIP_COMMON_CHUNKS` is a flag which prevents already generated chunks from being included again in the same page. This should only happen if you use more than one entrypoint per Django template (multiple `render_bundle` calls). By enabling this, you can get the same default behavior of the [HtmlWebpackPlugin](https://webpack.js.org/plugins/html-webpack-plugin/). The same caveats apply as when using `skip_common_chunks` on `render_bundle`, see that section below for more details.
+
 Here's a simple example of loading from an external url:
 
   ```py
@@ -239,7 +241,7 @@ The public path is based on `webpack.config.js` [output.publicPath](https://webp
 Please note that this approach will use the original asset file, and not a post-processed one from the Webpack pipeline, in case that file had gone through such flow (i.e.: You've imported an image on the React side and used it there, the file used within the React components will probably have a hash string on its name, etc. This processed file will be different than the one you'll grab with `webpack_static`).
 
 ### Use `skip_common_chunks` on `render_bundle`
-You can use the parameter `skip_common_chunks=True` to specify that you don't want an already generated chunk be included again in the same page. This should only happen if you use more than one entrypoint per Django template (multiple `render_bundle` calls). By using `skip_common_chunks=True`, you can get the same default behavior of the [HtmlWebpackPlugin](https://webpack.js.org/plugins/html-webpack-plugin/).
+You can use the parameter `skip_common_chunks=True` or `skip_common_chunks=False` to override the global `SKIP_COMMON_CHUNKS` setting for a specific bundle.
 
 In order for this option to work, `django-webpack-loader` requires the `request` object to be in the context, to be able to keep track of the generated chunks.
 

tests/app/tests/test_webpack.py

@@ -527,9 +527,13 @@ def test_emits_warning_on_no_request_in_jinja2engine(self):
         _warn_mock.assert_not_called()
         _warn_mock.reset_mock()
 
-    def _assert_common_chunks_duplicated_djangoengine(self, template=None):
-        if template is None:
-            raise TypeError('Django template is a required argument')
+    def _assert_common_chunks_duplicated_djangoengine(self, template):
+        """
+        Verify that any common chunks between two bundles are duplicated in
+        the HTML markup.
+
+        :param template: A Django template instance
+        """
         request = self.factory.get(path='/')
         asset_vendor = (
             '<script src="/static/django_webpack_loader_bundles/vendors.js" >'
@@ -550,9 +554,13 @@ def _assert_common_chunks_duplicated_djangoengine(self, template=None):
         self.assertEqual(rendered_template.count(asset_app2), 1)
         self.assertEqual(rendered_template.count(asset_vendor), 2)
 
-    def _assert_common_chunks_not_duplicated_djangoengine(self, template=None):
-        if template is None:
-            raise TypeError('Django template is a required argument')
+    def _assert_common_chunks_not_duplicated_djangoengine(self, template):
+        """
+        Verify that any common chunks between two bundles are not duplicated in
+        the HTML markup.
+
+        :param template: A Django template instance
+        """
         request = self.factory.get(path='/')
         asset_vendor = (
             '<script src="/static/django_webpack_loader_bundles/vendors.js" >'
@@ -573,9 +581,13 @@ def _assert_common_chunks_not_duplicated_djangoengine(self, template=None):
         self.assertEqual(rendered_template.count(asset_app2), 1)
         self.assertEqual(rendered_template.count(asset_vendor), 1)
 
-    def _assert_common_chunks_duplicated_jinja2engine(self, view=None):
-        if view is None:
-            raise TypeError('TemplateView is a required argument')
+    def _assert_common_chunks_duplicated_jinja2engine(self, view):
+        """
+        Verify that any common chunks between two bundles are duplicated in
+        the HTML markup.
+
+        :param view: A Django TemplateView instance
+        """
         settings = {
             'TEMPLATES': [
                 {
@@ -612,9 +624,13 @@ def _assert_common_chunks_duplicated_jinja2engine(self, view=None):
         self.assertIsNotNone(used_tags, msg=(
             '_webpack_loader_used_tags should be a property of request!'))
 
-    def _assert_common_chunks_not_duplicated_jinja2engine(self, view=None):
-        if view is None:
-            raise TypeError('TemplateView is a required argument')
+    def _assert_common_chunks_not_duplicated_jinja2engine(self, view):
+        """
+        Verify that any common chunks between two bundles are not duplicated in
+        the HTML markup.
+
+        :param view: A Django TemplateView instance
+        """
         settings = {
             'TEMPLATES': [
                 {
@@ -651,8 +667,8 @@ def _assert_common_chunks_not_duplicated_jinja2engine(self, view=None):
         self.assertIsNotNone(used_tags, msg=(
             '_webpack_loader_used_tags should be a property of request!'))
 
-    def test_skip_common_chunks_djangoengine(self):
-        """Test case for deduplication of modules with the django engine."""
+    def test_skip_common_chunks_templatetag_djangoengine(self):
+        """Test case for deduplication of modules with the django engine via the render_bundle template tag."""
         self.compile_bundles('webpack.config.skipCommon.js')
 
         django_engine = engines['django']
@@ -670,15 +686,15 @@ def test_skip_common_chunks_djangoengine(self):
         self._assert_common_chunks_not_duplicated_djangoengine(nodups_template)
 
 
-    def test_skip_common_chunks_jinja2engine(self):
-        """Test case for deduplication of modules with the Jinja2 engine."""
+    def test_skip_common_chunks_templatetag_jinja2engine(self):
+        """Test case for deduplication of modules with the Jinja2 engine via the render_bundle template tag."""
         self.compile_bundles('webpack.config.skipCommon.js')
 
         view = TemplateView.as_view(template_name='home-deduplicated.jinja')
         self._assert_common_chunks_not_duplicated_jinja2engine(view)
 
     def test_skip_common_chunks_setting_djangoengine(self):
-        """Test case for deduplication of modules with the django engine."""
+        """The global setting should default to False and deduplicate chunks without changing the render_bundle template tag."""
         self.compile_bundles('webpack.config.skipCommon.js')
 
         django_engine = engines['django']
@@ -693,7 +709,7 @@ def test_skip_common_chunks_setting_djangoengine(self):
             self._assert_common_chunks_not_duplicated_djangoengine(dups_template)
 
     def test_skip_common_chunks_setting_jinja2engine(self):
-        """Test case for deduplication of modules with the Jinja2 engine."""
+        """The global setting should default to False and deduplicate chunks without changing the render_bundle template tag."""
         self.compile_bundles('webpack.config.skipCommon.js')
 
         view = TemplateView.as_view(template_name='home-duplicated.jinja')
@@ -704,7 +720,7 @@ def test_skip_common_chunks_setting_jinja2engine(self):
             self._assert_common_chunks_not_duplicated_jinja2engine(view)
 
     def test_skip_common_chunks_setting_can_be_overridden_djangoengine(self):
-        """Skip common chunks template tag options should take precedent over global setting."""
+        """The skip common chunks template tag parameters should take precedent over the global setting."""
         self.compile_bundles('webpack.config.skipCommon.js')
 
         django_engine = engines['django']
@@ -724,7 +740,7 @@ def test_skip_common_chunks_setting_can_be_overridden_djangoengine(self):
             self._assert_common_chunks_duplicated_djangoengine(dups_template)
 
     def test_skip_common_chunks_setting_can_be_overridden_jinja2engine(self):
-        """Test case for deduplication of modules with the Jinja2 engine."""
+        """The skip common chunks template tag parameters should take precedent over the global setting."""
         self.compile_bundles('webpack.config.skipCommon.js')
 
         view = TemplateView.as_view(template_name='home-deduplicated.jinja')
@@ -736,6 +752,7 @@ def test_skip_common_chunks_setting_can_be_overridden_jinja2engine(self):
             self._assert_common_chunks_duplicated_jinja2engine(view)
 
     def test_skip_common_chunks_missing_config(self):
+        """If the setting is not present we should default to allowing common chunks."""
         self.compile_bundles('webpack.config.skipCommon.js')
 
         loader = get_loader(DEFAULT_CONFIG)

webpack_loader/config.py

@@ -16,6 +16,8 @@
         'IGNORE': [r'.+\.hot-update.js', r'.+\.map'],
         'LOADER_CLASS': 'webpack_loader.loader.WebpackLoader',
         'INTEGRITY': False,
+        # Whenever the global setting for SKIP_COMMON_CHUNKS is changed, please
+        # update the fallback value in get_skip_common_chunks (utils.py).
         'SKIP_COMMON_CHUNKS': False,
     }
 }