doc_modes.pl

/*  Part of SWI-Prolog

    Author:        Jan Wielemaker
    E-mail:        J.Wielemaker@vu.nl
    WWW:           http://www.swi-prolog.org
    Copyright (c)  2006-2025, University of Amsterdam
                              VU University Amsterdam
                              CWI, Amsterdam
                              SWI-Prolog Solutions b.v.
    All rights reserved.

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    are met:

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       notice, this list of conditions and the following disclaimer.

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       notice, this list of conditions and the following disclaimer in
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       distribution.

    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
    "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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    FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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*/

:- module(pldoc_modes,
          [ process_modes/6,            % +Lines, +M, +FP, -Modes, -Av, -RLines
            compile_mode/2,             % +PlDocMode, +ModeTerm
            mode/2,                     % ?:Head, -Det
            is_mode/1,                  % @Mode
            mode_indicator/1,           % ?Atom
            modes_to_predicate_indicators/2, % +Modes, -PIs
            compile_clause/2            % +Term, +File:Line
          ]).
:- use_module(library(lists)).
:- use_module(library(apply)).
:- use_module(library(operators)).
:- use_module(library(error)).

/** <module> Analyse PlDoc mode declarations

This  module  analyzes  the  formal  part  of  the  documentation  of  a
predicate. The formal  part  is  processed   by  read_term/3  using  the
operator declarations in this module.

@author   Jan Wielemaker
@license  GPL
*/

:- op(750, xf, ...).                    % Repeated argument: Arg...
:- op(650, fx, +).                      % allow +Arg
:- op(650, fx, -).                      % allow -Arg
:- op(650, fx, ++).                     % allow ++Arg
:- op(650, fx, --).                     % allow --Arg
:- op(650, fx, ?).                      % allow ?Arg
:- op(650, fx, :).                      % allow :Arg
:- op(650, fx, @).                      % allow @Arg
:- op(650, fx, !).                      % allow !Arg
:- op(200, xf, //).                     % allow for Head// is det.

                 /*******************************
                 *             MODES            *
                 *******************************/

%!  process_modes(+Lines:lines, +Module, +FilePos,
%!                -Modes:list, -Args:list(atom),
%!                -RestLines:lines) is det.
%
%   Process the formal header lines  (upto   the  first blank line),
%   returning the remaining lines and  the   names  of the arguments
%   used in the various header lines.
%
%   @arg FilePos  Term File:Line with the position of comment
%   @arg Modes    List if mode(Head, Bindings) terms
%   @arg Args     List of argument-names appearing in modes

process_modes(Lines, Module, FilePos, ModeDecls, Vars, RestLines) :-
    mode_lines(Lines, ModeText, [], RestLines),
    modes(ModeText, Module, FilePos, ModeDecls),
    extract_varnames(ModeDecls, Vars0, []),
    sort(Vars0, Vars).

%!  mode_lines(+Lines, -ModeText:codes, ?ModeTail:codes, -Lines) is det.
%
%   Extract the formal header. For  %%/%!   comments  these  are all
%   lines starting with %%/%!. For /**   comments,  first skip empty
%   lines and then  take  all  lines   upto  the  first  blank line.
%   Skipping empty lines allows for comments using this style:
%
%     ==
%     /**
%      * predicate(+arg1:type1, ?arg2:type2) is det
%      ...
%     ==

mode_lines(Lines0, ModeText, ModeTail, Lines) :-
    percent_mode_line(Lines0, C, ModeText, ModeTail0, Lines1),
    !,
    percent_mode_lines(Lines1, C, ModeTail0, ModeTail, Lines).
mode_lines(Lines0, ModeText, ModeTail, Lines) :-
    empty_lines(Lines0, Lines1),
    non_empty_lines(Lines1, ModeText, ModeTail, Lines).

percent_mode_line([1-[C|L]|Lines], C, ModeText, ModeTail, Lines) :-
    percent_mode_char(C),
    append(L, [10|ModeTail], ModeText).

percent_mode_char(0'%).
percent_mode_char(0'!).

percent_mode_lines(Lines0, C, ModeText, ModeTail, Lines) :-
    percent_mode_line(Lines0, C, ModeText, ModeTail1, Lines1),
    !,
    percent_mode_lines(Lines1, C, ModeTail1, ModeTail, Lines).
percent_mode_lines(Lines, _, Mode, Mode, Lines).

empty_lines([_-[]|Lines0], Lines) :-
    !,
    empty_lines(Lines0, Lines).
empty_lines(Lines, Lines).

non_empty_lines([], ModeTail, ModeTail, []).
non_empty_lines([_-[]|Lines], ModeTail, ModeTail, Lines) :- !.
non_empty_lines([_-L|Lines0], ModeText, ModeTail, Lines) :-
    append(L, [10|ModeTail0], ModeText),
    non_empty_lines(Lines0, ModeTail0, ModeTail, Lines).


%!  modes(+Text:codes, +Module, +FilePos, -ModeDecls) is det.
%
%   Read mode declaration. This consists of a number of Prolog terms
%   which may or may not be closed by  a Prolog full-stop.
%
%   @arg Text             Input text as list of codes.
%   @arg Module           Module the comment comes from
%   @arg ModeDecls        List of mode(Term, Bindings)

modes(Text, Module, FilePos, Decls) :-
    prepare_module_operators(Module),
    modes(Text, FilePos, Decls).

modes(Text, FilePos, Decls) :-
    catch(read_mode_terms(Text, FilePos, '', Decls), E, true),
    (   var(E)
    ->  !
    ;   E = error(syntax_error(end_of_file), _)
    ->  fail
    ;   !, mode_syntax_error(E),
        Decls = []
    ).
modes(Text, FilePos, Decls) :-
    catch(read_mode_terms(Text, FilePos, ' . ', Decls), E, true),
    (   var(E)
    ->  !
    ;   mode_syntax_error(E),
        fail
    ).
modes(_, _, []).

%!  mode_syntax_error(+ErrorTerm) is det.
%
%   Print syntax errors in  mode   declarations.  Currently, this is
%   suppressed unless the flag =pldoc_errors= is specified.

mode_syntax_error(E) :-
    current_prolog_flag(pldoc_errors, true),
    !,
    print_message(warning, E).
mode_syntax_error(_).


read_mode_terms(Text, File:Line, End, Terms) :-
    format(string(S), '~s~w', [Text, End]),
    setup_call_cleanup(
        open_string(S, In),
        read_modes(In, File, Line, Terms),
        close(In)).

read_modes(In, File, Line, Terms) :-
    (   atom(File)                  % can be PceEmacs buffer
    ->  set_stream(In, file_name(File))
    ;   true
    ),
    stream_property(In, position(Pos0)),
    set_line(Pos0, Line, Pos),
    set_stream_position(In, Pos),
    read_modes(In, Terms).

set_line('$stream_position'(CharC, _, LinePos, ByteC),
         Line,
         '$stream_position'(CharC, Line, LinePos, ByteC)).

read_modes(In, Terms) :-
    read_mode_term(In, Term0),
    read_modes(Term0, In, Terms).

read_modes(mode(end_of_file,[]), _, []) :- !.
read_modes(T0, In, [T0|Rest]) :-
    T0 = mode(Mode, _),
    is_mode(Mode),
    !,
    read_mode_term(In, T1),
    read_modes(T1, In, Rest).
read_modes(mode(Mode, Bindings), In, Modes) :-
    maplist(call, Bindings),
    print_message(warning, pldoc(invalid_mode(Mode))),
    read_mode_term(In, T1),
    read_modes(T1, In, Modes).

read_mode_term(In, mode(Term, Bindings)) :-
    read_term(In, Term,
              [ variable_names(Bindings),
                module(pldoc_modes)
              ]).


%!  prepare_module_operators is det.
%
%   Import operators from current source module.

:- dynamic
    prepared_module/2.

prepare_module_operators(Module) :-
    (   prepared_module(Module, _)
    ->  true
    ;   unprepare_module_operators,
        public_operators(Module, Ops),
        (   Ops \== []
        ->  push_operators(Ops, Undo),
            asserta(prepared_module(Module, Undo))
        ;   true
        )
    ).

unprepare_module_operators :-
    forall(retract(prepared_module(_, Undo)),
           pop_operators(Undo)).


%!  public_operators(+Module, -List:list(op(Pri,Assoc,Name))) is det.
%
%   List is the list of operators exported from Module through its
%   module header.

public_operators(Module, List) :-
    module_property(Module, exported_operators(List)),
    !.
public_operators(_, []).


%!  extract_varnames(+Bindings, -VarNames, ?VarTail) is det.
%
%   Extract the variables names.
%
%   @arg Bindings         Nested list of Name=Var
%   @arg VarNames         List of variable names
%   @arg VarTail          Tail of VarNames

extract_varnames([], VN, VN) :- !.
extract_varnames([H|T], VN0, VN) :-
    !,
    extract_varnames(H, VN0, VN1),
    extract_varnames(T, VN1, VN).
extract_varnames(mode(_, Bindings), VN0, VN) :-
    !,
    extract_varnames(Bindings, VN0, VN).
extract_varnames(Name=_, [Name|VN], VN).

%!  compile_mode(+Mode, -Compiled) is det.
%
%   Compile  a  PlDoc  mode  declararion   into  a  term  mode(Head,
%   Determinism).
%
%   @arg Mode       List if mode-terms.  See process_modes/6.

compile_mode(mode(Mode, _Bindings), Compiled) :-
    compile_mode2(Mode, Compiled).

compile_mode2(Var, _) :-
    var(Var),
    !,
    throw(error(instantiation_error,
                context(_, 'PlDoc: Mode declaration expected'))).
compile_mode2(Head0 is Det, mode(Head, Det)) :-
    !,
    dcg_expand(Head0, Head).
compile_mode2(Head0, mode(Head, unknown)) :-
    dcg_expand(Head0, Head).

dcg_expand(M:Head0, M:Head) :-
    atom(M),
    !,
    dcg_expand(Head0, Head).
dcg_expand(//(Head0), Head) :-
    !,
    Head0 =.. [Name|List0],
    maplist(remove_argname, List0, List1),
    append(List1, [?list, ?list], List2),
    Head =.. [Name|List2].
dcg_expand(Head0, Head) :-
    remove_argnames(Head0, Head).

remove_argnames(Var, _) :-
    var(Var),
    !,
    instantiation_error(Var).
remove_argnames(M:Head0, M:Head) :-
    !,
    must_be(atom, M),
    remove_argnames(Head0, Head).
remove_argnames(Head0, Head) :-
    functor(Head0, Name, Arity),
    functor(Head, Name, Arity),
    remove_argnames(0, Arity, Head0, Head).

remove_argnames(Arity, Arity, _, _) :- !.
remove_argnames(I0, Arity, H0, H) :-
    I is I0 + 1,
    arg(I, H0, A0),
    remove_argname(A0, A),
    arg(I, H, A),
    remove_argnames(I, Arity, H0, H).

remove_argname(T, ?(any)) :-
    var(T),
    !.
remove_argname(...(T0), ...(T)) :-
    !,
    remove_argname(T0, T).
remove_argname(A0, A) :-
    mode_ind(A0, M, A1),
    !,
    remove_aname(A1, A2),
    mode_ind(A, M, A2).
remove_argname(A0, ?A) :-
    remove_aname(A0, A).

remove_aname(Var, any) :-
    var(Var),
    !.
remove_aname(_:Type, Type) :- !.


%!  mode(:Head, ?Det) is nondet.
%
%   True if there is a mode-declaration for Head with Det.
%
%   @arg  Head    Callable term.  Arguments are a mode-indicator
%                   followed by a type.
%   @arg  Det     One of =unknown=, =det=, =semidet=, or =nondet=.

:- module_transparent
    mode/2.

mode(Head, Det) :-
    var(Head),
    !,
    current_module(M),
    '$c_current_predicate'(_, M:'$mode'(_,_)),
    M:'$mode'(H,Det),
    qualify(M,H,Head).
mode(M:Head, Det) :-
    current_module(M),
    '$c_current_predicate'(_, M:'$mode'(_,_)),
    M:'$mode'(Head,Det).

qualify(system, H, H) :- !.
qualify(user,   H, H) :- !.
qualify(M,      H, M:H).


%!  is_mode(@Head) is semidet.
%
%   True if Head is a valid mode-term.

is_mode(Var) :-
    var(Var), !, fail.
is_mode(Head is Det) :-
    !,
    is_det(Det),
    is_head(Head).
is_mode(Head) :-
    is_head(Head).

is_det(Var) :-
    var(Var), !, fail.
is_det(failure).
is_det(det).
is_det(semidet).
is_det(nondet).
is_det(multi).
is_det(undefined).

is_head(Var) :-
    var(Var), !, fail.
is_head(//(Head)) :-
    !,
    is_mhead(Head).
is_head(M:(//(Head))) :-
    !,
    atom(M),
    is_phead(Head).
is_head(Head) :-
    is_mhead(Head).

is_mhead(M:Head) :-
    !,
    atom(M),
    is_phead(Head).
is_mhead(Head) :-
    is_phead(Head).

is_phead(Head) :-
    callable(Head),
    functor(Head, _Name, Arity),
    is_head_args(0, Arity, Head).

is_head_args(A, A, _) :- !.
is_head_args(I0, Arity, Head) :-
    I is I0 + 1,
    arg(I, Head, Arg),
    is_head_arg(Arg),
    is_head_args(I, Arity, Head).

is_head_arg(Arg) :-
    var(Arg),
    !.
is_head_arg(...(Arg)) :-
    !,
    is_head_arg_nva(Arg).
is_head_arg(Arg) :-
    is_head_arg_nva(Arg).

is_head_arg_nva(Arg) :-
    var(Arg),
    !.
is_head_arg_nva(Arg) :-
    Arg =.. [Ind,Arg1],
    mode_indicator(Ind),
    is_head_arg(Arg1).
is_head_arg_nva(Arg:Type) :-
    var(Arg),
    is_type(Type).

is_type(Type) :-
    var(Type),
    !.                   % allow polypmorphic types.
is_type(Type) :-
    callable(Type).

%!  mode_indicator(?Ind:atom) is nondet.
%
%   Our defined argument-mode indicators

mode_indicator(+).                      % Instantiated to type
mode_indicator(-).                      % Output argument
mode_indicator(++).                     % Ground
mode_indicator(--).                     % Must be unbound
mode_indicator(?).                      % Partially instantiated to type
mode_indicator(:).                      % Meta-argument (implies +)
mode_indicator(@).                      % Not instantiated by pred
mode_indicator(!).                      % Mutable term

mode_ind(+(X), +, X).
mode_ind(-(X), -, X).
mode_ind(++(X), ++, X).
mode_ind(--(X), --, X).
mode_ind(?(X), ?, X).
mode_ind(:(X), :, X).
mode_ind(@(X), @, X).
mode_ind(!(X), !, X).


%!  modes_to_predicate_indicators(+Modes:list, -PI:list) is det.
%
%   Create a list of predicate indicators represented by Modes. Each
%   predicate indicator is  of  the   form  atom/integer  for normal
%   predicates or atom//integer for DCG rules.
%
%   @arg Modes    Mode-list as produced by process_modes/5
%   @arg PI       List of Name/Arity or Name//Arity without duplicates

modes_to_predicate_indicators(Modes, PIs) :-
    modes_to_predicate_indicators2(Modes, PIs0),
    list_to_set(PIs0, PIs).

modes_to_predicate_indicators2([], []).
modes_to_predicate_indicators2([mode(H,_B)|T0], [PI|T]) :-
    mode_to_pi(H, PI),
    modes_to_predicate_indicators2(T0, T).

mode_to_pi(Head is _Det, PI) :-
    !,
    head_to_pi(Head, PI).
mode_to_pi(Head, PI) :-
    head_to_pi(Head, PI).

head_to_pi(M:Head, M:PI) :-
    atom(M),
    !,
    head_to_pi(Head, PI).
head_to_pi(//(Head), Name//Arity) :-
    !,
    functor(Head, Name, Arity).
head_to_pi(Head, Name/Arity) :-
    functor(Head, Name, Arity).

%!  compile_clause(:Term, +FilePos) is det.
%
%   Add a clause to the  compiled   program.  Unlike  assert/1, this
%   associates the clause with the   given source-location, makes it
%   static code and removes the  clause   if  the  file is reloaded.
%   Finally,  as  we  create  clauses   one-by-one,  we  define  our
%   predicates as discontiguous.
%
%   @arg Term     Clause-term
%   @arg FilePos  Term of the form File:Line, where File is a
%                   canonical filename.

compile_clause(Term, File:Line) :-
    '$set_source_module'(SM, SM),
    strip_module(SM:Term, M, Plain),
    clause_head(Plain, Head),
    functor(Head, Name, Arity),
    multifile(M:(Name/Arity)),
    (   M == SM
    ->  Clause = Term
    ;   Clause = M:Term
    ),
    '$store_clause'('$source_location'(File, Line):Clause, File).

clause_head((Head :- _Body), Head) :- !.
clause_head(Head, Head).


                 /*******************************
                 *             MESSAGES         *
                 *******************************/

:- multifile
    prolog:message//1.

prolog:message(pldoc(invalid_mode(Mode))) -->
    [ 'Invalid mode declaration in PlDoc comment: ~q'-[Mode] ].