Add accept HTML attribute to documents form file input.

app/helpers/documentables_helper.rb

@@ -16,6 +16,12 @@ module DocumentablesHelper
     documentable.class.accepted_content_types
   end
 
+  def accepted_content_types_extensions(documentable)
+    documentable.class.accepted_content_types
+                .collect{ |content_type| ".#{content_type.split("/").last}" }
+                .join(",")
+  end  
+
   def humanized_accepted_content_types(documentable)
     documentable.class.accepted_content_types
                 .collect{ |content_type| content_type.split("/").last }

app/views/documents/_form.html.erb

@@ -16,7 +16,9 @@
 
     <div class="small-12 column">
       <div class="file-name">
-        <%= f.file_field :attachment, label: false, class: 'show-for-sr' %>
+        <%= f.file_field :attachment,
+                         accept: accepted_content_types_extensions(@document.documentable),
+                         label: false, class: 'show-for-sr' %>
         <%= f.label :attachment, t("documents.form.attachment_label"), class: 'button hollow' %>
         <p><%= document_attachment_file_name(@document) %></p>
       </div>