On Fri, Apr 13, 2012 at 09:45, Magnus Bäck <ba...
> I'm looking into customizing the Prolog rules for determining whether a
> change can be submitted, but in between the scarce documentation and my
> limited Prolog skills, it turned out rather difficult.
> I tried putting a rules.pl with simply
> in refs/meta/config of my test project and expected all changes to be
> marked as submittable, but I didn't note any change in Gerrit's
Leaving it like this means P is unbound, so we probably should have
failed everything rather than had no real change in behavior.
> Looking at ChangeControl.java I suspect it's because the
> expected result isn't a boolean yes/no but rather a more intricate
> structure listing which labels and ranges are okay. Trying
> submit_rule(P) :- label(_, ok(_)).
This doesn't work either, as you said. Its functionally the same as
the first example you gave, except it tried to call that label/2
predicate which may wind up failing.
> instead effectively deleted all approval categories. Not just from the
> set of approval categories available to me for scoring but the approval
> categories displayed in the UI.
And that is why those got deleted, because label/2 probably failed so
we had no result.
> Can someone please shed some light on this? What's the expected result
> of these predicates?
The argument of submit_rule is actually an output, it needs to be a
submit term. Suppose we have only 1 label, and we always want it to be
CR = label('Code-Review', ok(_)),
P = submit(CR).
I could have written this as:
CR = label('Code-Review', ok(_)).
Or even as:
But always allowing submit isn't useful, instead we want to also check
permissions and have possible alternatives. Something like this:
% A rejection from any reviewer, blocks submit.
max_with_block('Code-Review', -2, 2, reject(User)),
CR = label('Code-Review', reject(User)),
% If a reviewer approved the change, its OK.
max_with_block('Code-Review', -2, 2, ok(Reviewer)),
CR = label('Code-Review', ok(Reviewer)),
% If the change owner marks it To Be Reviewed, OK.
check_label_range_permission('TBR', 1, ok(Owner)),
TBR = label('TBR', ok(Owner)),
% Permit valid reviewers to set the Code-Review label.
submit_rule(submit(label('Code-Review', S))) :-
max_with_block('Code-Review', -2, 2, S).
% Permit owners to set the TBR label.
submit_rule(submit(label('TBR', S)) :-
S = need(1).
Remember, in Prolog "," works something like "boolean and" and the
interpreter keeps trying different alternate paths until it finds one
that works. The ! at the end of the first 3 rules are necessary to
prevent the interpreter from looking at the later cases that allow
using different labels. The above examples are completely untested.