added config loader for webpack and view helper for hashed assets (#174)

* added config loader for webpack and view helper for hashed assets

* cleanup

* rm javascript_tag, replaced with asset_path

* ASSETS instead of assets

* added better error messages

Author: shreyas-satish

baseframe/__init__.py

@@ -3,6 +3,7 @@
 from __future__ import absolute_import
 from pytz import timezone, UTC
 from flask import g, Blueprint, request, current_app
+import json
 from coaster.assets import split_namespec
 from flask_assets import Environment, Bundle
 from flask_caching import Cache
@@ -172,6 +173,23 @@ def init_app(self, app, requires=[], ext_requires=[], bundle_js=None, bundle_css
         app.assets.register('css_all', css_all)
         app.register_blueprint(self, static_subdomain=subdomain)
 
+        # Optional config for a client app to use a manifest file
+        # to load fingerprinted assets
+        # If used with webpack, the client app is expected to specify its own webpack.config.js
+        # Set `ASSETS_MANIFEST_PATH` in `app.config` to the path for `manifest.json`.
+        # Eg: "static/build/manifest.json"
+        # Set `ASSET_BASE_PATH` in `app.config` to the path in which the compiled assets are present.
+        # Eg: "static/build"
+        if app.config.get('ASSET_MANIFEST_PATH'):
+            # Load assets into config from a manifest file
+            with app.open_resource(app.config['ASSET_MANIFEST_PATH']) as f:
+                asset_bundles = json.loads(f.read())
+                if app.config.get('assets'):
+                    raise ValueError("Loading assets via a manifest file needs the `ASSETS` config key to be unused")
+                app.config['assets'] = {}
+                for asset_key, asset_path in asset_bundles['assets'].items():
+                    app.config['assets'][asset_key] = asset_path
+
         app.config.setdefault('CACHE_KEY_PREFIX', 'flask_cache_' + app.name + '/')
         nwcacheconfig = dict(app.config)
         nwcacheconfig['CACHE_KEY_PREFIX'] = 'networkbar_'

baseframe/views.py

@@ -85,11 +85,22 @@ def ext_assets(assets):
         return gen_assets_url(assets)
 
 
+def asset_path(bundle_key):
+    if not current_app.config.get('ASSET_BASE_PATH'):
+        raise LookupError("Missing base path for assets. Ensure `ASSET_BASE_PATH` is set to the path where the asset can be found. Eg: `/static/`")
+    if not current_app.config.get('assets').get(bundle_key):
+        raise LookupError("Missing asset file for {bundle}.".format(bundle=bundle_key))
+    return '{path}/{bundle}'.format(
+        path=current_app.config['ASSET_BASE_PATH'],
+        bundle=current_app.config['assets'][bundle_key])
+
+
 @baseframe.app_context_processor
 def baseframe_context():
     return {
         'networkbar_links': networkbar_links,
         'csrf_token': generate_csrf,
+        'asset_path': asset_path,
     }