[enh] plugins: client side dependency support

searx/plugins/__init__.py

                   ('description', str),
                   ('default_on', bool))
 
+optional_attrs = (('js_dependencies', tuple),
+                  ('css_dependencies', tuple))
+
 
 class Plugin():
     default_on = False
                 if not hasattr(plugin, plugin_attr) or not isinstance(getattr(plugin, plugin_attr), plugin_attr_type):
                     logger.critical('missing attribute "{0}", cannot load plugin: {1}'.format(plugin_attr, plugin))
                     exit(3)
+            for plugin_attr, plugin_attr_type in optional_attrs:
+                if not hasattr(plugin, plugin_attr) or not isinstance(getattr(plugin, plugin_attr), plugin_attr_type):
+                    setattr(plugin, plugin_attr, plugin_attr_type())
             plugin.id = plugin.name.replace(' ', '_')
             self.plugins.append(plugin)
 

searx/templates/oscar/base.html

     <meta name="viewport" content="width=device-width, initial-scale=1 , maximum-scale=1.0, user-scalable=1" />
     {% block meta %}{% endblock %}
     <title>{% block title %}{% endblock %}searx</title>
-    
+
     <link rel="stylesheet" href="{{ url_for('static', filename='css/bootstrap.min.css') }}" type="text/css" />
-    <link rel="stylesheet" href="{{ url_for('static', filename='css/oscar.min.css') }}" type="text/css" />  
+    <link rel="stylesheet" href="{{ url_for('static', filename='css/oscar.min.css') }}" type="text/css" />
     <link rel="stylesheet" href="{{ url_for('static', filename='css/leaflet.min.css') }}" type="text/css" />
+    {% for css in styles %}
+        <link rel="stylesheet" href="{{ url_for('static', filename=css) }}" type="text/css" />
+    {% endfor %}
 
     <!-- HTML5 Shim and Respond.js IE8 support of HTML5 elements and media queries -->
     <!--[if lt IE 9]>
       <script src="{{ url_for('static', filename='js/html5shiv.min.js') }}"></script>
       <script src="{{ url_for('static', filename='js/respond.min.js') }}"></script>
     <![endif]-->
-    
+
     <link rel="shortcut icon" href="{{ url_for('static', filename='img/favicon.png') }}" />
 
     {% block styles %}
     {% endblock %}
 
     <link title="searx" type="application/opensearchdescription+xml" rel="search" href="{{ url_for('opensearch') }}"/>
-    
+
     <script type="text/javascript">
         searx = {};
         searx.method = "{{ method or 'POST' }}";
     {% if autocomplete %}<script src="{{ url_for('static', filename='js/typeahead.bundle.min.js') }}"></script>{% endif %}
     <script src="{{ url_for('static', filename='js/require-2.1.15.min.js') }}"></script>
     <script src="{{ url_for('static', filename='js/searx.min.js') }}"></script>
+    {% for script in scripts %}
+        <script src="{{ url_for('static', filename=script) }}"></script>
+    {% endfor %}
 </body>
 </html>

searx/webapp.py

 
     kwargs['cookies'] = request.cookies
 
+    kwargs['scripts'] = set()
+    for plugin in request.user_plugins:
+        for script in plugin.js_dependencies:
+            kwargs['scripts'].add(script)
+
+    kwargs['styles'] = set()
+    for plugin in request.user_plugins:
+        for css in plugin.css_dependencies:
+            kwargs['styles'].add(css)
+
     return render_template(
         '{}/{}'.format(kwargs['theme'], template_name), **kwargs)