The layout-diff job does a validation layout for HEAD and HEAD^ and then uses diff. Possible scenarii are:

• layout validations fail -> build failure
• diff -> build failure

• layout ok and no diff -> build success

That maps to:

success-message:

'Please carefully review the Zuul layout difference before deploying/merging.'

failure-message:

'No layout change apparently. Nonetheless, please carefully review before deploying/merging.'

We should swap them and change the 'Please carefully...' message to 'FAILURE difference is being introduced, please carefully review the difference'.

We can guarantee the layout is valid with the job integration-zuul-layoutvalidation and make it a parent of the layout diff in Zuul config:

check:

• integration-zuul-layoutvalidation: integration-zuul-layoutdiff

This way the layoutdiff would only be triggered after the layout has been validated, so we now a failure must be caused by diff exiting non zero, and hence a diff has been introduced.