goal_expansion/2 not being called

I’m trying to workaround the format/2-3 predicates not accepting an atom in the first argument by using the goal_expansion/2 predicate as follows:

var program = 
	":- use_module(library(format))." +
	"goal_expansion(format(A,L),format(Cs,L)) :- atom(A), atom_chars(A,Cs)." +
	"foo :- format('~w~n',[hello]).";
session.consult( program );

session.query( "foo." );
session.answers( x => console.log( pl.format_answer(x) ) );

But the goal_expansion/2 predicate doesn’t seem to be called:

$ node ./tp.js 
uncaught exception: error(type_error(list, ~w~n), /(format_, 2))
false.

I also tried, with no success, using separate consult calls:

session.consult( ":- use_module(library(format))." );
session.consult( "goal_expansion(format(A,L),format(Cs,L)) :- atom(A), atom_chars(A,Cs)." );
session.consult( "foo :- format('~w~n',[hello])." );

The expanding a goal is expected to recursively call the goal_expansion/2 predicate until a fixed-point is reached. But in this case it seems like the predicate is never called.

P.S. I have a simpler alternative to workaround the limitations of the format/2-3 predicates.

[jariazavalverde]

Fixed. It was a bug due to changing the default value of the quoted writing option to false.

TODO: At the moment, term and goal expansion only looks for predicates term_expansion/2 and goal_expansion/2 defined in the user module.

[triska]

One example is from library(clpz), which works with SICStus:

with_local_attributes(Vars, Goal, Result) :-
        catch((Goal,
               maplist(del_all_attrs, Vars),
               % reset all attributes, only the result matters
               throw(local_attributes(Result,Vars))),
              local_attributes(Result,Vars),
              true).

Here, Goal is invoked dynamically, and it is used with goals that need goal expansion. This goal expansion is not applied at compile time, because the Prolog compiler only sees with_local_attributes/3 invoked.

However, now that I think about it, with a suitable meta_predicate/1 declaration for with_local_attributes/3, the compiler could probably look into the argument, and expand it too? That would solve the issue without any overhead at runtime.

That being said, I would still find runtime goal expansion for the call/N family of predicates desirable, and it can be implemented with close to no overhead. If it is too slow, I would regard that as a sign that the implementation needs to be improved so that it becomes fast.