+++ This bug was initially created as a clone of Bug #55392 +++

VE caches the diff, which means if no content is changed, the user is shown
a) a stale diff and is allowed to proceed with saving the page, which means they are then
b) the page with their saved changes only
The user is unaware that they have overwritten another persons changes.

Steps to reproduce:

1. Create a page with some two lines https://en.wikipedia.org/w/index.php?title=User:John_Vandenberg/test&oldid=573748285
2. Open the page in two VE windows
3. In the second window, alter the first line and save https://en.wikipedia.org/w/index.php?title=User:John_Vandenberg/test&oldid=576079696
4. In the first window, alter the first line and review changes (the diff only shows the first line being modified against the page contents from step 3)
5. In the second window, add some lines and save https://en.wikipedia.org/w/index.php?title=User:John_Vandenberg/test&oldid=576079807
6. In the first window, review changes, and cancel the save (the diff is the same as in step 5; the VE page content doesnt change)
7. In the first window, save

Expected results:
In step 7, the diff should be refreshed even though the page content has not been modified.

Actual results:
The diff from step 5 is displayed in step 7.

Version: unspecified
Severity: minor
See Also:
https://bugzilla.wikimedia.org/show_bug.cgi?id=55392