AWight found cases of the new WD2 code apparently producing incorrect results. Given that this is being rolled out and a regression in compiled code can crash production servers, this was bugging me so much that I decided to look into it some more. Results so far:

1. https://en.wikipedia.beta.wmflabs.org/w/index.php?title=User:Adamw/diff_large_chunks&type=revision&diff=394825&oldid=394824&diffmode=source

This has a large number of changes, but the total count of added or deleted lines (i.e. candidates for moves) is below the threshold, so the move detection stuff is active. It may look confusing but this is intentional and OK.

2. https://en.wikipedia.beta.wmflabs.org/w/index.php?title=User:Adamw/diff_large_chunks&diff=394824&oldid=394823&diffmode=source

This output is incorrect. The number of added+deleted lines crosses the default threshold (added+deleted lines >100). The move detection should be disabled, but it still runs.

3. https://en.wikipedia.beta.wmflabs.org/w/index.php?title=User:Adamw/diff_large_chunks&diff=394823&oldid=394822

This is also incorrect. Detection shouldn't run, same as 2).

3b) https://test.wikipedia.org/w/index.php?title=User%3AAdamw%2Fdiff_large_chunks&type=revision&diff=398154&oldid=398153

This is the same diff as 3, but on test instead of beta, and the output is also wrong.

I imported 2) and 3) on my local installation with current Wikidiff2. Both show the correct output. Possible explanations:

• Something related to PHP7, although I don't see how this could be an issue. My local installation runs PHP7.
• Could it be some kind of caching issue?
• The new Wikidiff2 version might not be properly rolled out, or
• The server processes might not have been restarted after the rollout, so the PHP extension .so was not reloaded.