Move Webassets in a plugin

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)