Debugging Prolog

[Kenny Ho]

Hi,

I am new to Prolog and I am trying to create some custom rules.  (I am essentially trying to implement some kind of file whitelist on submit.)  What is the best way to debug Prolog with Gerrit?  I know there is the Prolog shell but it doesn't have gerrit facts.  I also know that I can do the "test-submit rule " on the server but when something failed I am not quite sure where to go.  (Sometimes it prints error_log, which I can check, but sometimes I just get "Processing of prolog script failed" because my script is wrong.)  I know this is a very "imperative" things to ask, but is there a way I can 'print' something from within rules.pl?  (let's say if I want to find out what I am getting back from commit_delta/3 w.r.t. the new path part, how can I do that?)

[Kenny Ho]

So I ended up using the label field as a debug output.  For example:

submit_rule(S) :-
  gerrit:commit_delta('.*', T, P, _),
  S =.. [submit | [label(P, need(_))] ].

As for the whitelisting part, I got to a point where I can create an atom with the name of the non-whitelisted file, but when I try to make a need-label from it I get an error.

whitelisted(Ls, F, Out) :-

  regex_matches('^t.*', F),!;

  regex_matches('^m.*', F),!;

  atom_concat('Need-whitelist-', F, Wl),

  Out = Wl.

submit_rule(S) :-

  gerrit:default_submit(X),

  X =.. [submit | Ls],

  gerrit:commit_delta('.*', T, P, _), 

  whitelisted(Ls, P, Wlabels),

  S =.. [submit | [label(Wlabels, need(_))] ].

For example, if I have three files in the commit and one of them is "bob.txt", the above code will give me three labels: one with "Need-whitelist-bob.txt" and two others two label with empty string.  How can I eliminate the 2 empty labels and combine them into one submit (with the labels returned from default_submit?  Can anyone help?

[Kenny Ho]

Actually... let me clarify the question a bit.  When commit_delta/3 (http://gerrit-review.googlesource.com/Documentation/prolog-change-facts.html) return on a patch that has multiple changes, is returning a list or something else?  From what I can observe so far, seems like it's something else as the whitelisted predicate is being run multiple times (once for each path that matches the commit_delta regex.)  How would I "reduce" these multiple 'runs' back into one action?  (Namely, to add the "need-whitelist" label or not.)

[Saša Živkov]

On Fri, Sep 19, 2014 at 10:35 PM, Kenny Ho <y2k...@gmail.com> wrote:

So I ended up using the label field as a debug output.

 

This is a good idea and the one I wanted to propose. 

If I remember well, before the "test-submit rule" command was refactored to use the REST code

it was possible to return anything from the submit_rule and display it raw at the client side.

Looks like this feature is lost and we must take care to always return a proper submit term in order

to get something useful back to the client.

For example:

submit_rule(S) :-
  gerrit:commit_delta('.*', T, P, _),
  S =.. [submit | [label(P, need(_))] ].

As for the whitelisting part, I got to a point where I can create an atom with the name of the non-whitelisted file, but when I try to make a need-label from it I get an error.

whitelisted(Ls, F, Out) :-

The "Ls" is not used... you can remove it.

 

  regex_matches('^t.*', F),!;

  regex_matches('^m.*', F),!;

Looks like here is your problem (the OR operator ';')

Even if neither if the two above matches the evaluation will continue as you have the OR operator

and the atom_concat will succeed etc...

Try instead:

whitelisted(Ls, F, Out) :-

    (regex_matches('^t.*', F); regex_matches('^m.*', F)) ,

  atom_concat('Need-whitelist-', F, Wl),

  Out = Wl.

 

  atom_concat('Need-whitelist-', F, Wl),

  Out = Wl.

submit_rule(S) :-

  gerrit:default_submit(X),

  X =.. [submit | Ls],

  gerrit:commit_delta('.*', T, P, _), 

  whitelisted(Ls, P, Wlabels),

  S =.. [submit | [label(Wlabels, need(_))] ].

For example, if I have three files in the commit and one of them is "bob.txt", the above code will give me three labels: one with "Need-whitelist-bob.txt" and two others two label with empty string.  How can I eliminate the 2 empty labels and combine them into one submit (with the labels returned from default_submit?  Can anyone help?

On Friday, September 19, 2014 2:12:41 PM UTC-4, Kenny Ho wrote:

Hi,

I am new to Prolog and I am trying to create some custom rules.  (I am essentially trying to implement some kind of file whitelist on submit.)  What is the best way to debug Prolog with Gerrit?  I know there is the Prolog shell but it doesn't have gerrit facts.  I also know that I can do the "test-submit rule " on the server but when something failed I am not quite sure where to go.  (Sometimes it prints error_log, which I can check, but sometimes I just get "Processing of prolog script failed" because my script is wrong.)  I know this is a very "imperative" things to ask, but is there a way I can 'print' something from within rules.pl?  (let's say if I want to find out what I am getting back from commit_delta/3 w.r.t. the new path part, how can I do that?)

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[Kenny Ho]

I ended up making the whitelist work with this (but since I am completely new to Prolog, I am not sure if it's the best/efficient way to go about it:

whitelisted(B, P) :-

  regex_matches('refs/meta/config', B), regex_matches('rules.pl', P);

  regex_matches('^t.*', P);

  %  regex_matches('^b.*', P);

  regex_matches('^m.*', P).

add_need_whitelist(In, Out) :-

  gerrit:commit_delta('.*', T, P, _),

  gerrit:change_branch(B),

  \+ whitelisted(B, P), %if not in the whitelist, stop it

  Out = [ label('Need-whitelisting', impossible(_)) | In ], !. %cut once it's true

add_need_whitelist(In, Out) :-

  gerrit:change_owner(A),

  Out = [ label('Need-whitelisting', ok(A)) | In ].

submit_rule(S) :-

  gerrit:default_submit(X),

  X =.. [submit | Ls],

  add_need_whitelist(Ls, R),

  S =.. [submit | R ].

I also tries to make things a bit more modular but taking the whitelisted(B, P) :- part to another file.  But when I try to use consult or include inside rules.pl, I get error.  Is that something not supported with Prolog on Gerrit?

The error:

Caused by: com.googlecode.prolog_cafe.lang.TermException: permission_error(assertz(:(user,:-(consult(w

hitelist),true))),modify,static_procedure,:(user,/(consult,1)),_2C3C1A6F)

Kenny

[Saša Živkov]

On Wed, Oct 8, 2014 at 4:46 PM, Kenny Ho <y2k...@gmail.com> wrote:

I ended up making the whitelist work with this (but since I am completely new to Prolog, I am not sure if it's the best/efficient way to go about it:

whitelisted(B, P) :-

  regex_matches('refs/meta/config', B), regex_matches('rules.pl', P);

  regex_matches('^t.*', P);

  %  regex_matches('^b.*', P);

  regex_matches('^m.*', P).

add_need_whitelist(In, Out) :-

  gerrit:commit_delta('.*', T, P, _),

  gerrit:change_branch(B),

  \+ whitelisted(B, P), %if not in the whitelist, stop it

  Out = [ label('Need-whitelisting', impossible(_)) | In ], !. %cut once it's true

add_need_whitelist(In, Out) :-

  gerrit:change_owner(A),

  Out = [ label('Need-whitelisting', ok(A)) | In ].

submit_rule(S) :-

  gerrit:default_submit(X),

  X =.. [submit | Ls],

  add_need_whitelist(Ls, R),

  S =.. [submit | R ].

I also tries to make things a bit more modular but taking the whitelisted(B, P) :- part to another file.  But when I try to use consult or include inside rules.pl, I get error.  Is that something not supported with Prolog on Gerrit?

 

I don't think that we support include and/or consult.