This ticket collects and groups possible error states of the bridge app, in order to group and not forget them. We have the privilege to decide if we want to cater to each of these individually (for the known unknowns) or we let them fall back to the generic error screen which we'll have to create regardless (for the unknown unknowns).

Please add more error states here and feel free to group them as groups emerge.

Scenarios:

• entity loading failed
  • server does not respond (no internet)
  • server responds with bad data (e.g. some html)
  • server responds with server error (e.g. 500)
  • server responds with bad request or similar (e.g. 400 if hrefRegExp is badly done and Q0 requested)
  • entity does not exist at server
  • entity does not exist at server, but is a redirect
• property label loading failed (possible options mentioned during T227759 were: trying to load it again, showing the property id with a little message, showing the generic error handler)
• data type not supported (yet) - as tracked by T231204: track Bridge openings by property datatype
• snak type novalue/somevalue not yet supported
• more than one statement in statement group not yet supported
• there is no statement for the property on the entity yet
• saving failed
  • timeout
  • generic - rudimentary UI message was added during T230339: Show error in case saving failed
  • configured tag(s) don’t actually exist on repo wiki (cf. T227003: Add an edit tag parameter and tag the edits made via data bridge with "Data Bridge")
  • assert user failed (the user is/was logged-in in wikipedia/client, but is not/no longer logged in wikidata/repo) – tell them to log in and repeat their edit (T231887#5537210)
  • edit conflict
• purging the parser cache, after saving was a success, has failed. --> The user might see outdated data when reloading

Other

• page is protected at client
• page is protected at repo