template: boolean attribute can now be specified when importing a script, and default to "defer"

src/tools/common/template.py

@@ -155,17 +155,20 @@ class ScriptsHandler(object):
         self.scripts = []  # we don't use a set because order may be important
         dummy, self.theme, self.is_default_theme = renderer.getThemeData(template_path)
 
-    def include(self, library_name):
+    def include(self, library_name, attribute='defer'):
         """Mark that a script need to be imported.
 
         Must be used before base.html is extended, as <script> are generated there.
         If called several time with the same library, it will be imported once.
         @param library_name(unicode): name of the library to import
+        @param loading:
         """
+        if attribute not in ('defer', 'async', ''):
+            raise exceptions.DataError(_(u'Invalid attribute, please use one of "defer", "async" or ""'))
         if library_name.endswith('.js'):
             library_name = library_name[:-3]
         if library_name not in self.scripts:
-            self.scripts.append(library_name)
+            self.scripts.append((library_name, attribute))
         return u''
 
     def generate_scripts(self):
@@ -174,14 +177,17 @@ class ScriptsHandler(object):
         @return (unicode): <scripts> HTML tags
         """
         scripts = []
-        tpl = u'<script src={src}></script>'
-        for library in self.scripts:
+        tpl = u'<script src={src} {attribute}></script>'
+        for library, attribute in self.scripts:
             path = self.renderer.getStaticPath(library, self.template_root_dir, self.theme, self.is_default_theme, '.js')
             if path is None:
                 log.warning(_(u"Can't find {}.js javascript library").format(library))
                 continue
             path = os.path.join(self.root_path, path)
-            scripts.append(tpl.format(src=quoteattr(path)))
+            scripts.append(tpl.format(
+                src = quoteattr(path),
+                attribute = attribute,
+                ))
         return safe(u'\n'.join(scripts))