add initial support for offline engines && command engine

searx/plugins/oa_doi_rewrite.py

@@ -35,6 +35,9 @@ def get_doi_resolver(args, preference_doi_resolver):
 
 
 def on_result(request, search, result):
+    if 'parsed_url' not in result:
+        return True
+
     doi = extract_doi(result['parsed_url'])
     if doi and len(doi) < 50:
         for suffix in ('/', '.pdf', '/full', '/meta', '/abstract'):