Move Webassets in a plugin

pelican/__init__.py

@@ -158,11 +158,6 @@ class Pelican(object):
 
         writer = self.get_writer()
 
-        # pass the assets environment to the generators
-        if self.settings['WEBASSETS']:
-            generators[1].env.assets_environment = generators[0].assets_env
-            generators[2].env.assets_environment = generators[0].assets_env
-
         for p in generators:
             if hasattr(p, 'generate_output'):
                 p.generate_output(writer)

pelican/generators.py

@@ -465,37 +465,6 @@ class StaticGenerator(Generator):
             copy(path, source, os.path.join(output_path, destination),
                  final_path, overwrite=True)
 
-    def generate_context(self):
-
-        if self.settings['WEBASSETS']:
-            from webassets import Environment as AssetsEnvironment
-
-            # Define the assets environment that will be passed to the
-            # generators. The StaticGenerator must then be run first to have
-            # the assets in the output_path before generating the templates.
-
-            # Let ASSET_URL honor Pelican's RELATIVE_URLS setting.
-            # Hint for templates:
-            # Current version of webassets seem to remove any relative
-            # paths at the beginning of the URL. So, if RELATIVE_URLS
-            # is on, ASSET_URL will start with 'theme/', regardless if we
-            # set assets_url here to './theme/' or to 'theme/'.
-            # XXX However, this breaks the ASSET_URL if user navigates to
-            # a sub-URL, e.g. if he clicks on a category. To workaround this
-            # issue, I use
-            #     <link rel="stylesheet" href="{{ SITEURL }}/{{ ASSET_URL }}">
-            # instead of
-            #     <link rel="stylesheet" href="{{ ASSET_URL }}">
-            if self.settings.get('RELATIVE_URLS'):
-                assets_url = './theme/'
-            else:
-                assets_url = self.settings['SITEURL'] + '/theme/'
-            assets_src = os.path.join(self.output_path, 'theme')
-            self.assets_env = AssetsEnvironment(assets_src, assets_url)
-
-            if logging.getLevelName(logger.getEffectiveLevel()) == "DEBUG":
-                self.assets_env.debug = True
-
     def generate_output(self, writer):
 
         self._copy_paths(self.settings['STATIC_PATHS'], self.path,

pelican/plugins/assets.py

@@ -0,0 +1,64 @@
+# -*- coding: utf-8 -*-
+"""
+Asset management plugin for Pelican
+===================================
+
+This plugin allows you to use the `webassets`_ module to manage assets such as
+CSS and JS files.
+
+Hint for templates: Current version of webassets seems to remove any relative
+paths at the beginning of the URL. So, if ``RELATIVE_URLS`` is on,
+``ASSET_URL`` will start with ``theme/``, regardless if we set ``assets_url``
+here to ``./theme/`` or to ``theme/``.
+
+However, this breaks the ``ASSET_URL`` if user navigates to a sub-URL, e.g. if
+he clicks on a category. A workaround for this issue is to use::
+
+    <link rel="stylesheet" href="{{ SITEURL }}/{{ ASSET_URL }}">
+
+instead of::
+
+    <link rel="stylesheet" href="{{ ASSET_URL }}">
+
+.. _webassets: https://webassets.readthedocs.org/
+
+"""
+
+import os
+import logging
+
+from pelican import signals
+from webassets import Environment
+from webassets.ext.jinja2 import AssetsExtension
+
+
+def add_jinja2_ext(pelican):
+    """Add Webassets to Jinja2 extensions in Pelican settings."""
+
+    pelican.settings['JINJA_EXTENSIONS'].append(AssetsExtension)
+
+
+def create_assets_env(generator):
+    """Define the assets environment and pass it to the generator."""
+
+    logger = logging.getLogger(__name__)
+
+    # Let ASSET_URL honor Pelican's RELATIVE_URLS setting.
+    if generator.settings.get('RELATIVE_URLS'):
+        assets_url = './theme/'
+    else:
+        assets_url = generator.settings['SITEURL'] + '/theme/'
+    assets_src = os.path.join(generator.output_path, 'theme')
+
+    generator.env.assets_environment = Environment(assets_src, assets_url)
+
+    if logging.getLevelName(logger.getEffectiveLevel()) == "DEBUG":
+        generator.env.assets_environment.debug = True
+
+
+def register():
+    """Plugin registration."""
+
+    signals.initialized.connect(add_jinja2_ext)
+    signals.article_generator_init.connect(create_assets_env)
+    signals.pages_generator_init.connect(create_assets_env)

pelican/settings.py

@@ -76,7 +76,6 @@ _DEFAULT_CONFIG = {'PATH': '.',
                    'ARTICLE_PERMALINK_STRUCTURE': '',
                    'TYPOGRIFY': False,
                    'SUMMARY_MAX_LENGTH': 50,
-                   'WEBASSETS': False,
                    'PLUGINS': [],
                    'MARKDOWN_EXTENSIONS': ['toc', ],
                    'TEMPLATE_PAGES': {}
@@ -187,16 +186,7 @@ def configure_settings(settings):
 
     if 'LESS_GENERATOR' in settings:
         logger.warn("The LESS_GENERATOR setting has been removed in favor "
-                    "of WEBASSETS")
+                    "of the Webassets plugin")
-
-    if 'WEBASSETS' in settings and settings['WEBASSETS'] is not False:
-        try:
-            from webassets.ext.jinja2 import AssetsExtension
-            settings['JINJA_EXTENSIONS'].append(AssetsExtension)
-        except ImportError:
-            logger.warn("You must install the webassets module to use "
-                        "WEBASSETS")
-            settings['WEBASSETS'] = False
 
     if 'OUTPUT_SOURCES_EXTENSION' in settings:
         if not isinstance(settings['OUTPUT_SOURCES_EXTENSION'], str):

tests/test_generators.py

@@ -257,7 +257,7 @@ class TestWebAssets(unittest.TestCase):
         self.settings = read_settings(override={
             'PATH': os.path.join(CUR_DIR, 'content', 'TestCategory'),
             'OUTPUT_PATH': self.temp_path,
-            'WEBASSETS': True,
+            'PLUGINS': ['pelican.plugins.assets', ],
             'THEME': self.theme_dir,
         })
         pelican = Pelican(settings=self.settings)