While trying to reproduce bug 68472 I triggered network errors:
- View a Flow board on local MW server.
- Open browser
- On server rename api.php to api_BROKEN.php
- Click Summrize topic, or click Reply and then click [Reply], etc.
Result: nothing is reported to the user despite the api response being 404 Not Found. The console reports a JS error
TypeError: result.error is undefined
if ( result.error.prev_revision ) in apiHandlers[ handlerName ] fail().
In this failure case, there's no result.error , hence the JS error. Even if avoided, Flow displays "undefioned" in its pink errorbox because there's nothing in result.error.info; it seems that if there's a network error the failure information is in result.exception ("Not found") and result.textStatus ("error"). (It sucks that different levels of API failure put information in different pieces of the result object.)