aboutsummaryrefslogtreecommitdiffstats
path: root/lib/syntax_tools/src/epp_dodger.erl
blob: 6b0f2034f85acd3836663d1873b40c7af13595d7 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
%% =====================================================================
%% This library is free software; you can redistribute it and/or modify
%% it under the terms of the GNU Lesser General Public License as
%% published by the Free Software Foundation; either version 2 of the
%% License, or (at your option) any later version.
%%
%% This library is distributed in the hope that it will be useful, but
%% WITHOUT ANY WARRANTY; without even the implied warranty of
%% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
%% Lesser General Public License for more details.
%%
%% You should have received a copy of the GNU Lesser General Public
%% License along with this library; if not, write to the Free Software
%% Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
%% USA
%%
%% $Id$
%%
%% @copyright 2001-2006 Richard Carlsson
%% @author Richard Carlsson <richardc@it.uu.se>
%% @end
%% =====================================================================

%% @doc `epp_dodger' - bypasses the Erlang preprocessor.
%%
%% <p>This module tokenises and parses most Erlang source code without
%% expanding preprocessor directives and macro applications, as long as
%% these are syntactically "well-behaved". Because the normal parse
%% trees of the `erl_parse' module cannot represent these things
%% (normally, they are expanded by the Erlang preprocessor {@link
%% //stdlib/epp} before the parser sees them), an extended syntax tree
%% is created, using the {@link erl_syntax} module.</p>


%% NOTES:
%%
%% * It's OK if the result does not parse - then at least nothing
%% strange happens, and the user can resort to full preprocessing.
%% However, we must avoid generating a token stream that is accepted by
%% the parser, but has a different meaning than the intended. A typical
%% example is when someone uses token-level string concatenation with
%% macros, as in `"foo" ?bar' (where `?bar' expands to a string). If we
%% replace the tokens `? bar' with `( ... )', to preserve precedence,
%% the result will be parsed as an application `"foo" ( ... )' and cause
%% trouble later on. We must detect such cases and report an error.
%% 
%% * It is pointless to add a mechanism for tracking which macros are
%% known to take arguments, and which are known to take no arguments,
%% since a lot of the time we will not have seen the macro definition
%% anyway (it's usually in a header file). Hence, we try to use
%% heuristics instead. In most cases, the token sequence `? foo ('
%% indicates that it is a call of a macro that is supposed to take
%% arguments, but e.g., in the context `: ? foo (', the argument list
%% typically belongs to a remote function call, as in `m:?f(...)' and
%% should be parsed as `m:(?f)(...)' unless it is actually a try-clause
%% pattern such as `throw:?f(...) ->'.
%% 
%% * We do our best to make macros without arguments pass the parsing
%% stage transparently. Atoms are accepted in most contexts, but
%% variables are not, so we use only atoms to encode these macros.
%% Sadly, the parsing sometimes discards even the line number info from
%% atom tokens, so we can only use the actual characters for this.
%%
%% * We recognize `?m(...' at the start of a form and prevent this from
%% being interpreted as a macro with arguments, since it is probably a
%% function definition. Likewise with attributes `-?m(...'.

-module(epp_dodger).

-export([parse_file/1, quick_parse_file/1, parse_file/2,
	 quick_parse_file/2, parse/1, quick_parse/1, parse/2,
	 quick_parse/2, parse/3, quick_parse/3, parse_form/2,
	 parse_form/3, quick_parse_form/2, quick_parse_form/3,
	 format_error/1, tokens_to_string/1]).


%% The following should be: 1) pseudo-uniquely identifiable, and 2)
%% cause nice looking error messages when the parser has to give up.

-define(macro_call, '? <macro> (').
-define(atom_prefix, "? ").
-define(var_prefix, "?,").
-define(pp_form, '?preprocessor declaration?').


%% @type errorinfo() = {ErrorLine::integer(),
%%                      Module::atom(),
%%                      Descriptor::term()}.
%% 
%% This is a so-called Erlang I/O ErrorInfo structure; see the {@link
%% //stdlib/io} module for details.

-type errorinfo() :: term(). % {integer(), atom(), term()}.

-type option() :: atom() | {atom(), term()}.

%% =====================================================================
%% @spec parse_file(File) -> {ok, Forms} | {error, errorinfo()}
%%       File = file:filename()
%%       Forms = [erl_syntax:syntaxTree()]
%% 
%% @equiv parse_file(File, [])

-spec parse_file(file:filename()) ->
        {'ok', erl_syntax:forms()} | {'error', errorinfo()}.

parse_file(File) ->
    parse_file(File, []).

%% @spec parse_file(File, Options) -> {ok, Forms} | {error, errorinfo()}
%%       File = file:filename()
%%       Options = [term()]
%%       Forms = [erl_syntax:syntaxTree()]
%% 
%% @doc Reads and parses a file. If successful, `{ok, Forms}'
%% is returned, where `Forms' is a list of abstract syntax
%% trees representing the "program forms" of the file (cf.
%% `erl_syntax:is_form/1'). Otherwise, `{error, errorinfo()}' is
%% returned, typically if the file could not be opened. Note that
%% parse errors show up as error markers in the returned list of
%% forms; they do not cause this function to fail or return
%% `{error, errorinfo()}'.
%%
%% Options:
%% <dl>
%%   <dt>{@type {no_fail, boolean()@}}</dt>
%%   <dd>If `true', this makes `epp_dodger' replace any program forms
%%   that could not be parsed with nodes of type `text' (see {@link
%%   erl_syntax:text/1}), representing the raw token sequence of the
%%   form, instead of reporting a parse error. The default value is
%%   `false'.</dd>
%%   <dt>{@type {clever, boolean()@}}</dt>
%%   <dd>If set to `true', this makes `epp_dodger' try to repair the
%%   source code as it seems fit, in certain cases where parsing would
%%   otherwise fail. Currently, it inserts `++'-operators between string
%%   literals and macros where it looks like concatenation was intended.
%%   The default value is `false'.</dd>
%% </dl>
%%
%% @see parse/2
%% @see quick_parse_file/1
%% @see erl_syntax:is_form/1

-spec parse_file(file:filename(), [option()]) ->
        {'ok', erl_syntax:forms()} | {'error', errorinfo()}.

parse_file(File, Options) ->
    parse_file(File, fun parse/3, Options).

%% @spec quick_parse_file(File) -> {ok, Forms} | {error, errorinfo()}
%%       File = file:filename()
%%       Forms = [erl_syntax:syntaxTree()]
%%
%% @equiv quick_parse_file(File, [])

-spec quick_parse_file(file:filename()) ->
        {'ok', erl_syntax:forms()} | {'error', errorinfo()}.

quick_parse_file(File) ->
    quick_parse_file(File, []).

%% @spec quick_parse_file(File, Options) ->
%%           {ok, Forms} | {error, errorinfo()}
%%       File = file:filename()
%%       Options = [term()]
%%       Forms = [erl_syntax:syntaxTree()]
%%
%% @doc Similar to {@link parse_file/2}, but does a more quick-and-dirty
%% processing of the code. Macro definitions and other preprocessor
%% directives are discarded, and all macro calls are replaced with
%% atoms. This is useful when only the main structure of the code is of
%% interest, and not the details. Furthermore, the quick-parse method
%% can usually handle more strange cases than the normal, more exact
%% parsing.
%%
%% Options: see {@link parse_file/2}. Note however that for
%% `quick_parse_file/2', the option `no_fail' is `true' by default.
%%
%% @see quick_parse/2
%% @see parse_file/2

-spec quick_parse_file(file:filename(), [option()]) ->
        {'ok', erl_syntax:forms()} | {'error', errorinfo()}.

quick_parse_file(File, Options) ->
    parse_file(File, fun quick_parse/3, Options ++ [no_fail]).

parse_file(File, Parser, Options) ->
    case file:open(File, [read]) of
        {ok, Dev} ->
            try Parser(Dev, 1, Options)
            after ok = file:close(Dev)
	    end;
        {error, _} = Error ->
            Error
    end.


%% =====================================================================
%% @spec parse(IODevice) -> {ok, Forms} | {error, errorinfo()}
%% @equiv parse(IODevice, 1)

-spec parse(file:io_device()) -> {'ok', erl_syntax:forms()}.

parse(Dev) ->
    parse(Dev, 1).

%% @spec parse(IODevice, StartLine) -> {ok, Forms} | {error, errorinfo()}
%%       IODevice = pid()
%%       StartLine = integer()
%%       Forms = [erl_syntax:syntaxTree()]
%%
%% @equiv parse(IODevice, StartLine, [])
%% @see parse/1

-spec parse(file:io_device(), integer()) -> {'ok', erl_syntax:forms()}.

parse(Dev, L) ->
    parse(Dev, L, []).

%% @spec parse(IODevice, StartLine, Options) ->
%%           {ok, Forms} | {error, errorinfo()}
%%       IODevice = pid()
%%       StartLine = integer()
%%       Options = [term()]
%%       Forms = [erl_syntax:syntaxTree()]
%%
%% @doc Reads and parses program text from an I/O stream. Characters are
%% read from `IODevice' until end-of-file; apart from this, the
%% behaviour is the same as for {@link parse_file/2}. `StartLine' is the
%% initial line number, which should be a positive integer.
%%
%% @see parse/2
%% @see parse_file/2
%% @see parse_form/2
%% @see quick_parse/3

-spec parse(file:io_device(), integer(), [option()]) ->
        {'ok', erl_syntax:forms()}.

parse(Dev, L0, Options) ->
    parse(Dev, L0, fun parse_form/3, Options).

%% @spec quick_parse(IODevice) -> {ok, Forms} | {error, errorinfo()}
%% @equiv quick_parse(IODevice, 1)

-spec quick_parse(file:io_device()) ->
        {'ok', erl_syntax:forms()}.

quick_parse(Dev) ->
    quick_parse(Dev, 1).

%% @spec quick_parse(IODevice, StartLine) ->
%%           {ok, Forms} | {error, errorinfo()}
%%       IODevice = pid()
%%       StartLine = integer()
%%       Forms = [erl_syntax:syntaxTree()]
%%
%% @equiv quick_parse(IODevice, StartLine, [])
%% @see quick_parse/1

-spec quick_parse(file:io_device(), integer()) ->
        {'ok', erl_syntax:forms()}.

quick_parse(Dev, L) ->
    quick_parse(Dev, L, []).

%% @spec (IODevice, StartLine, Options) ->
%%           {ok, Forms} | {error, errorinfo()}
%%       IODevice = pid()
%%       StartLine = integer()
%%       Options = [term()]
%%       Forms = [erl_syntax:syntaxTree()]
%% 
%% @doc Similar to {@link parse/3}, but does a more quick-and-dirty
%% processing of the code. See {@link quick_parse_file/2} for details.
%%
%% @see quick_parse/2
%% @see quick_parse_file/2
%% @see quick_parse_form/2
%% @see parse/3

-spec quick_parse(file:io_device(), integer(), [option()]) ->
        {'ok', erl_syntax:forms()}.

quick_parse(Dev, L0, Options) ->
    parse(Dev, L0, fun quick_parse_form/3, Options).

parse(Dev, L0, Parser, Options) ->
    parse(Dev, L0, [], Parser, Options).

parse(Dev, L0, Fs, Parser, Options) ->
    case Parser(Dev, L0, Options) of
        {ok, none, L1} ->
            parse(Dev, L1, Fs, Parser, Options);
        {ok, F, L1} ->
            parse(Dev, L1, [F | Fs], Parser, Options);
        {error, IoErr, L1} ->
            parse(Dev, L1, [{error, IoErr} | Fs], Parser, Options);
        {eof, _L1} ->
            {ok, lists:reverse(Fs)}
    end.


%% =====================================================================
%% @spec parse_form(IODevice, StartLine) -> {ok, Form, LineNo}
%%                                        | {eof, LineNo}
%%                                        | {error, errorinfo(), LineNo}
%%       IODevice = pid()
%%       StartLine = integer()
%%       Form = erl_syntax:syntaxTree()
%%       LineNo = integer()
%%
%% @equiv parse_form(IODevice, StartLine, [])
%%
%% @see quick_parse_form/2

-spec parse_form(file:io_device(), integer()) ->
        {'ok', erl_syntax:forms(), integer()}
      | {'eof', integer()} | {'error', errorinfo(), integer()}.

parse_form(Dev, L0) ->
    parse_form(Dev, L0, []).

%% @spec parse_form(IODevice, StartLine, Options) ->
%%           {ok, Form, LineNo}
%%         | {eof, LineNo}
%%         | {error, errorinfo(), LineNo}
%% 
%%       IODevice = pid()
%%       StartLine = integer()
%%       Options = [term()]
%%       Form = erl_syntax:syntaxTree()
%%       LineNo = integer()
%%
%% @doc Reads and parses a single program form from an I/O stream.
%% Characters are read from `IODevice' until an end-of-form
%% marker is found (a period character followed by whitespace), or until
%% end-of-file; apart from this, the behaviour is similar to that of
%% `parse/3', except that the return values also contain the
%% final line number given that `StartLine' is the initial
%% line number, and that `{eof, LineNo}' may be returned.
%%
%% @see parse/3
%% @see parse_form/2
%% @see quick_parse_form/3

-spec parse_form(file:io_device(), integer(), [option()]) ->
        {'ok', erl_syntax:forms(), integer()}
      | {'eof', integer()} | {'error', errorinfo(), integer()}.

parse_form(Dev, L0, Options) ->
    parse_form(Dev, L0, fun normal_parser/2, Options).

%% @spec quick_parse_form(IODevice, StartLine) ->
%%           {ok, Form, LineNo}
%%         | {eof, LineNo}
%%         | {error, errorinfo(), LineNo}
%%       IODevice = pid()
%%       StartLine = integer()
%%       Form = erl_syntax:syntaxTree() | none
%%       LineNo = integer()
%%
%% @equiv quick_parse_form(IODevice, StartLine, [])
%%
%% @see parse_form/2

-spec quick_parse_form(file:io_device(), integer()) ->
        {'ok', erl_syntax:forms(), integer()}
      | {'eof', integer()} | {'error', errorinfo(), integer()}.

quick_parse_form(Dev, L0) ->
    quick_parse_form(Dev, L0, []).

%% @spec quick_parse_form(IODevice, StartLine, Options) ->
%%           {ok, Form, LineNo}
%%         | {eof, LineNo}
%%         | {error, errorinfo(), LineNo}
%%
%%       IODevice = pid()
%%       StartLine = integer()
%%       Options = [term()]
%%       Form = erl_syntax:syntaxTree()
%%       LineNo = integer()
%%
%% @doc Similar to {@link parse_form/3}, but does a more quick-and-dirty
%% processing of the code. See {@link quick_parse_file/2} for details.
%%
%% @see parse/3
%% @see quick_parse_form/2
%% @see parse_form/3

-spec quick_parse_form(file:io_device(), integer(), [option()]) ->
        {'ok', erl_syntax:forms(), integer()}
      | {'eof', integer()} | {'error', errorinfo(), integer()}.

quick_parse_form(Dev, L0, Options) ->
    parse_form(Dev, L0, fun quick_parser/2, Options).

-record(opt, {clever = false :: boolean()}).

parse_form(Dev, L0, Parser, Options) ->
    NoFail = proplists:get_bool(no_fail, Options),
    Opt = #opt{clever = proplists:get_bool(clever, Options)},
    case io:scan_erl_form(Dev, "", L0) of
        {ok, Ts, L1} ->
            case catch {ok, Parser(Ts, Opt)} of
                {'EXIT', Term} ->
                    {error, io_error(L1, {unknown, Term}), L1};
                {error, Term} ->
		    IoErr = io_error(L1, Term),
		    {error, IoErr, L1};
                {parse_error, _IoErr} when NoFail ->
		    {ok, erl_syntax:set_pos(
			   erl_syntax:text(tokens_to_string(Ts)),
			   start_pos(Ts, L1)),
		     L1};
                {parse_error, IoErr} ->
		    {error, IoErr, L1};
                {ok, F} ->
                    {ok, F, L1}
            end;
        {error, _IoErr, _L1} = Err -> Err;
        {eof, _L1} = Eof -> Eof
    end.

io_error(L, Desc) ->
    {L, ?MODULE, Desc}.

start_pos([T | _Ts], _L) ->
    element(2, T);
start_pos([], L) ->
    L.

%% Exception-throwing wrapper for the standard Erlang parser stage

parse_tokens(Ts) ->
    parse_tokens(Ts, fun fix_form/1).

parse_tokens(Ts, Fix) ->
    case erl_parse:parse_form(Ts) of
        {ok, Form} ->
            Form;
        {error, IoErr} ->
	    case Fix(Ts) of
		{form, Form} ->
		    Form;
		{retry, Ts1, Fix1} ->
		    parse_tokens(Ts1, Fix1);
		error ->
		    throw({parse_error, IoErr})
	    end
    end.

%% ---------------------------------------------------------------------
%% Quick scanning/parsing - deletes macro definitions and other
%% preprocessor directives, and replaces all macro calls with atoms.

quick_parser(Ts, _Opt) ->
    filter_form(parse_tokens(quickscan_form(Ts))).

quickscan_form([{'-', _L}, {atom, La, define} | _Ts]) ->
    kill_form(La);
quickscan_form([{'-', _L}, {atom, La, undef} | _Ts]) ->
    kill_form(La);
quickscan_form([{'-', _L}, {atom, La, include} | _Ts]) ->
    kill_form(La);
quickscan_form([{'-', _L}, {atom, La, include_lib} | _Ts]) ->
    kill_form(La);
quickscan_form([{'-', _L}, {atom, La, ifdef} | _Ts]) ->
    kill_form(La);
quickscan_form([{'-', _L}, {atom, La, ifndef} | _Ts]) ->
    kill_form(La);
quickscan_form([{'-', _L}, {atom, La, else} | _Ts]) ->
    kill_form(La);
quickscan_form([{'-', _L}, {atom, La, endif} | _Ts]) ->
    kill_form(La);
quickscan_form([{'-', L}, {'?', _}, {Type, _, _}=N | [{'(', _} | _]=Ts])
  when Type =:= atom; Type =:= var ->
    %% minus, macro and open parenthesis at start of form - assume that
    %% the macro takes no arguments; e.g. `-?foo(...).'
    quickscan_macros_1(N, Ts, [{'-', L}]);
quickscan_form([{'?', _L}, {Type, _, _}=N | [{'(', _} | _]=Ts])
  when Type =:= atom; Type =:= var ->
    %% macro and open parenthesis at start of form - assume that the
    %% macro takes no arguments (see scan_macros for details)
    quickscan_macros_1(N, Ts, []);
quickscan_form(Ts) ->
    quickscan_macros(Ts).

kill_form(L) ->
    [{atom, L, ?pp_form}, {'(', L}, {')', L}, {'->', L}, {atom, L, kill},
     {dot, L}].

quickscan_macros(Ts) ->
    quickscan_macros(Ts, []).

quickscan_macros([{'?',_}, {Type, _, A} | Ts], [{string, L, S} | As])
  when Type =:= atom; Type =:= var ->
    %% macro after a string literal: change to a single string
    {_, Ts1} = skip_macro_args(Ts),
    S1 = S ++ quick_macro_string(A),
    quickscan_macros(Ts1, [{string, L, S1} | As]);
quickscan_macros([{'?',_}, {Type, _, _}=N | [{'(',_}|_]=Ts],
		 [{':',_}|_]=As)
  when Type =:= atom; Type =:= var ->
    %% macro and open parenthesis after colon - check the token
    %% following the arguments (see scan_macros for details)
    Ts1 = case skip_macro_args(Ts) of
	      {_, [{'->',_} | _] = Ts2} -> Ts2;
	      {_, [{'when',_} | _] = Ts2} -> Ts2;
	      _ -> Ts    %% assume macro without arguments
	  end,
    quickscan_macros_1(N, Ts1, As);
quickscan_macros([{'?',_}, {Type, _, _}=N | Ts], As)
  when Type =:= atom; Type =:= var ->
    %% macro with or without arguments
    {_, Ts1} = skip_macro_args(Ts),
    quickscan_macros_1(N, Ts1, As);
quickscan_macros([T | Ts], As) ->
    quickscan_macros(Ts, [T | As]);
quickscan_macros([], As) ->
    lists:reverse(As).

%% (after a macro has been found and the arglist skipped, if any)
quickscan_macros_1({_Type, _, A}, [{string, L, S} | Ts], As) ->
    %% string literal following macro: change to single string
    S1 = quick_macro_string(A) ++ S,
    quickscan_macros(Ts, [{string, L, S1} | As]);
quickscan_macros_1({_Type, L, A}, Ts, As) ->
    %% normal case - just replace the macro with an atom
    quickscan_macros(Ts, [{atom, L, quick_macro_atom(A)} | As]).

quick_macro_atom(A) ->
    list_to_atom("?" ++ atom_to_list(A)).

quick_macro_string(A) ->
    "(?" ++ atom_to_list(A) ++ ")".

%% Skipping to the end of a macro call, tracking open/close constructs.
%% @spec (Tokens) -> {Skipped, Rest}

skip_macro_args([{'(',_}=T | Ts]) ->
    skip_macro_args(Ts, [')'], [T]);
skip_macro_args(Ts) ->
    {[], Ts}.

skip_macro_args([{'(',_}=T | Ts], Es, As) ->
    skip_macro_args(Ts, [')' | Es], [T | As]);
skip_macro_args([{'{',_}=T | Ts], Es, As) ->
    skip_macro_args(Ts, ['}' | Es], [T | As]);
skip_macro_args([{'[',_}=T | Ts], Es, As) ->
    skip_macro_args(Ts, [']' | Es], [T | As]);
skip_macro_args([{'<<',_}=T | Ts], Es, As) ->
    skip_macro_args(Ts, ['>>' | Es], [T | As]);
skip_macro_args([{'begin',_}=T | Ts], Es, As) ->
    skip_macro_args(Ts, ['end' | Es], [T | As]);
skip_macro_args([{'if',_}=T | Ts], Es, As) ->
    skip_macro_args(Ts, ['end' | Es], [T | As]);
skip_macro_args([{'case',_}=T | Ts], Es, As) ->
    skip_macro_args(Ts, ['end' | Es], [T | As]);
skip_macro_args([{'receive',_}=T | Ts], Es, As) ->
    skip_macro_args(Ts, ['end' | Es], [T | As]);
skip_macro_args([{'try',_}=T | Ts], Es, As) ->
    skip_macro_args(Ts, ['end' | Es], [T | As]);
skip_macro_args([{'cond',_}=T | Ts], Es, As) ->
    skip_macro_args(Ts, ['end' | Es], [T | As]);
skip_macro_args([{E,_}=T | Ts], [E], As) ->		%final close
    {lists:reverse([T | As]), Ts};
skip_macro_args([{E,_}=T | Ts], [E | Es], As) ->	%matching close
    skip_macro_args(Ts, Es, [T | As]);
skip_macro_args([T | Ts], Es, As) ->
    skip_macro_args(Ts, Es, [T | As]);
skip_macro_args([], _Es, _As) ->
    throw({error, macro_args}).

filter_form({function, _, ?pp_form, _,
	     [{clause, _, [], [], [{atom, _, kill}]}]}) ->
    none;
filter_form(T) ->
    T.


%% ---------------------------------------------------------------------
%% Normal parsing - try to preserve all information

normal_parser(Ts, Opt) ->
    rewrite_form(parse_tokens(scan_form(Ts, Opt))).

scan_form([{'-', _L}, {atom, La, define} | Ts], Opt) ->
    [{atom, La, ?pp_form}, {'(', La}, {')', La}, {'->', La},
     {atom, La, define} | scan_macros(Ts, Opt)];
scan_form([{'-', _L}, {atom, La, undef} | Ts], Opt) ->
    [{atom, La, ?pp_form}, {'(', La}, {')', La}, {'->', La},
     {atom, La, undef} | scan_macros(Ts, Opt)];
scan_form([{'-', _L}, {atom, La, include} | Ts], Opt) ->
    [{atom, La, ?pp_form}, {'(', La}, {')', La}, {'->', La},
     {atom, La, include} | scan_macros(Ts, Opt)];
scan_form([{'-', _L}, {atom, La, include_lib} | Ts], Opt) ->
    [{atom, La, ?pp_form}, {'(', La}, {')', La}, {'->', La},
     {atom, La, include_lib} | scan_macros(Ts, Opt)];
scan_form([{'-', _L}, {atom, La, ifdef} | Ts], Opt) ->
    [{atom, La, ?pp_form}, {'(', La}, {')', La}, {'->', La},
     {atom, La, ifdef} | scan_macros(Ts, Opt)];
scan_form([{'-', _L}, {atom, La, ifndef} | Ts], Opt) ->
    [{atom, La, ?pp_form}, {'(', La}, {')', La}, {'->', La},
     {atom, La, ifndef} | scan_macros(Ts, Opt)];
scan_form([{'-', _L}, {atom, La, else} | Ts], Opt) ->
    [{atom, La, ?pp_form}, {'(', La}, {')', La}, {'->', La},
     {atom, La, else} | scan_macros(Ts, Opt)];
scan_form([{'-', _L}, {atom, La, endif} | Ts], Opt) ->
    [{atom, La, ?pp_form}, {'(', La}, {')', La}, {'->', La},
     {atom, La, endif} | scan_macros(Ts, Opt)];
scan_form([{'-', L}, {'?', L1}, {Type, _, _}=N | [{'(', _} | _]=Ts], Opt)
  when Type =:= atom; Type =:= var ->
    %% minus, macro and open parenthesis at start of form - assume that
    %% the macro takes no arguments; e.g. `-?foo(...).'
    macro(L1, N, Ts, [{'-', L}], Opt);
scan_form([{'?', L}, {Type, _, _}=N | [{'(', _} | _]=Ts], Opt)
  when Type =:= atom; Type =:= var ->
    %% macro and open parenthesis at start of form - assume that the
    %% macro takes no arguments; probably a function declaration on the
    %% form `?m(...) -> ...', which will not parse if it is rewritten as
    %% `(?m(...)) -> ...', so it must be handled as `(?m)(...) -> ...'
    macro(L, N, Ts, [], Opt);
scan_form(Ts, Opt) ->
    scan_macros(Ts, Opt).

scan_macros(Ts, Opt) ->
    scan_macros(Ts, [], Opt).

scan_macros([{'?', _}=M, {Type, _, _}=N | Ts], [{string, L, _}=S | As],
 	    #opt{clever = true}=Opt)
  when Type =:= atom; Type =:= var ->
    %% macro after a string literal: be clever and insert ++
    scan_macros([M, N | Ts], [{'++', L}, S | As], Opt);
scan_macros([{'?', L}, {Type, _, _}=N | [{'(',_}|_]=Ts],
	    [{':',_}|_]=As, Opt)
  when Type =:= atom; Type =:= var ->
    %% macro and open parentheses after colon - probably a call
    %% `m:?F(...)' so the argument list might belong to the call, not
    %% the macro - but it could also be a try-clause pattern
    %% `...:?T(...) ->' - we need to check the token following the
    %% arguments to decide
    {Args, Rest} = skip_macro_args(Ts),
    case Rest of
	[{'->',_} | _] ->
	    macro_call(Args, L, N, Rest, As, Opt);
	[{'when',_} | _] ->
	    macro_call(Args, L, N, Rest, As, Opt);
	_ ->
	    macro(L, N, Ts, As, Opt)
    end;
scan_macros([{'?', L}, {Type, _, _}=N | [{'(',_}|_]=Ts], As, Opt)
  when Type =:= atom; Type =:= var ->
    %% macro with arguments
    {Args, Rest} = skip_macro_args(Ts),
    macro_call(Args, L, N, Rest, As, Opt);
scan_macros([{'?', L }, {Type, _, _}=N | Ts], As, Opt)
  when Type =:= atom; Type =:= var ->
    %% macro without arguments
    macro(L, N, Ts, As, Opt);
scan_macros([T | Ts], As, Opt) ->
    scan_macros(Ts, [T | As], Opt);
scan_macros([], As, _Opt) ->
    lists:reverse(As).

%% Rewriting to a call which will be recognized by the post-parse pass
%% (we insert parentheses to preserve the precedences when parsing).

macro(L, {Type, _, A}, Rest, As, Opt) ->
    scan_macros_1([], Rest, [{atom,L,macro_atom(Type,A)} | As], Opt).

macro_call([{'(',_}, {')',_}], L, {_, Ln, _}=N, Rest, As, Opt) ->
    {Open, Close} = parentheses(As),
    scan_macros_1([], Rest,
		  lists:reverse(Open ++ [{atom,L,?macro_call},
					 {'(',L}, N, {')',Ln}] ++ Close,
				As), Opt);
macro_call([{'(',_} | Args], L, {_, Ln, _}=N, Rest, As, Opt) ->
    {Open, Close} = parentheses(As),
    %% note that we must scan the argument list; it may not be skipped
    scan_macros_1(Args ++ Close,
		  Rest,
		  lists:reverse(Open ++ [{atom,L,?macro_call},
					 {'(',L}, N, {',',Ln}],
				As), Opt).

macro_atom(atom, A) ->
    list_to_atom(?atom_prefix ++ atom_to_list(A));
macro_atom(var, A) ->
    list_to_atom(?var_prefix ++ atom_to_list(A)).

%% don't insert parentheses after a string token, to avoid turning
%% `"string" ?macro' into a "function application" `"string"(...)'
%% (see note at top of file)
parentheses([{string, _, _} | _]) ->
    {[], []};
parentheses(_) ->
    {[{'(',0}], [{')',0}]}.

%% (after a macro has been found and the arglist skipped, if any)
scan_macros_1(Args, [{string, L, _} | _]=Rest, As,
	      #opt{clever = true}=Opt) ->
    %% string literal following macro: be clever and insert ++
    scan_macros(Args ++ [{'++', L} | Rest],  As, Opt);
scan_macros_1(Args, Rest, As, Opt) ->
    %% normal case - continue scanning
    scan_macros(Args ++ Rest, As, Opt).

rewrite_form({function, L, ?pp_form, _,
              [{clause, _, [], [], [{call, _, A, As}]}]}) ->
    erl_syntax:set_pos(erl_syntax:attribute(A, rewrite_list(As)), L);
rewrite_form({function, L, ?pp_form, _, [{clause, _, [], [], [A]}]}) ->
    erl_syntax:set_pos(erl_syntax:attribute(A), L);
rewrite_form(T) ->
    rewrite(T).

rewrite_list([T | Ts]) ->
    [rewrite(T) | rewrite_list(Ts)];
rewrite_list([]) ->
    [].

%% Note: as soon as we start using erl_syntax:subtrees/1 and similar
%% functions, we cannot assume that we know the exact representation of
%% the syntax tree anymore - we must use erl_syntax functions to analyze
%% and decompose the data.

rewrite(Node) ->
    case erl_syntax:type(Node) of
	atom ->
	    case atom_to_list(erl_syntax:atom_value(Node)) of
		?atom_prefix ++ As ->
		    A1 = list_to_atom(As),
		    N = erl_syntax:copy_pos(Node, erl_syntax:atom(A1)),
		    erl_syntax:copy_pos(Node, erl_syntax:macro(N));
		?var_prefix ++ As ->
		    A1 = list_to_atom(As),
		    N = erl_syntax:copy_pos(Node, erl_syntax:variable(A1)),
		    erl_syntax:copy_pos(Node, erl_syntax:macro(N));
		_ ->
		    Node
	    end;
	application ->
	    F = erl_syntax:application_operator(Node),
	    case erl_syntax:type(F) of
		atom ->
		    case erl_syntax:atom_value(F) of
			?macro_call ->
			    [A | As] = erl_syntax:application_arguments(Node),
			    M = erl_syntax:macro(A, rewrite_list(As)),
			    erl_syntax:copy_pos(Node, M);
			_ ->
			    rewrite_1(Node)
		    end;
		_ ->
		    rewrite_1(Node)
	    end;
	_ ->
	    rewrite_1(Node)
    end.

rewrite_1(Node) ->
    case erl_syntax:subtrees(Node) of
	[] ->
	    Node;
	Gs ->
	    Node1 = erl_syntax:make_tree(erl_syntax:type(Node),
					 [[rewrite(T) || T <- Ts]
					  || Ts <- Gs]),
	    erl_syntax:copy_pos(Node, Node1)
    end.

%% attempting a rescue operation on a token sequence for a single form
%% if it could not be parsed after the normal treatment

fix_form([{atom, _, ?pp_form}, {'(', _}, {')', _}, {'->', _},
	  {atom, _, define}, {'(', _} | _]=Ts) ->
    case lists:reverse(Ts) of
	[{dot, _}, {')', _} | _] ->
	    {retry, Ts, fun fix_define/1};
	[{dot, L} | Ts1] ->
	    Ts2 = lists:reverse([{dot, L}, {')', L} | Ts1]),
	    {retry, Ts2, fun fix_define/1};
	_ ->
	    error
    end;
fix_form(_Ts) ->
    error.

fix_define([{atom, L, ?pp_form}, {'(', _}, {')', _}, {'->', _},
	    {atom, La, define}, {'(', _}, N, {',', _} | Ts]) ->
    [{dot, _}, {')', _} | Ts1] = lists:reverse(Ts),
    S = tokens_to_string(lists:reverse(Ts1)),
    A = erl_syntax:set_pos(erl_syntax:atom(define), La),
    Txt = erl_syntax:set_pos(erl_syntax:text(S), La),
    {form, erl_syntax:set_pos(erl_syntax:attribute(A, [N, Txt]), L)};
fix_define(_Ts) ->
    error.

%% @spec tokens_to_string(Tokens::[term()]) -> string()
%% 
%% @doc Generates a string corresponding to the given token sequence.
%% The string can be re-tokenized to yield the same token list again.

-spec tokens_to_string([term()]) -> string().

tokens_to_string([{atom,_,A} | Ts]) ->
    io_lib:write_atom(A) ++ " " ++ tokens_to_string(Ts);
tokens_to_string([{string, _, S} | Ts]) ->
    io_lib:write_string(S) ++ " " ++ tokens_to_string(Ts);
tokens_to_string([{float, _, F} | Ts]) ->
    float_to_list(F) ++ " " ++ tokens_to_string(Ts);
tokens_to_string([{integer, _, N} | Ts]) ->
    integer_to_list(N) ++ " " ++ tokens_to_string(Ts);
tokens_to_string([{var, _, A} | Ts]) ->
    atom_to_list(A) ++ " " ++ tokens_to_string(Ts);
tokens_to_string([{dot, _} | Ts]) ->
    ".\n" ++ tokens_to_string(Ts);
tokens_to_string([{A, _} | Ts]) ->
    atom_to_list(A) ++ " " ++ tokens_to_string(Ts);
tokens_to_string([]) ->
    "".


%% @spec format_error(Descriptor::term()) -> string()
%% @hidden
%% @doc Callback function for formatting error descriptors. Not for
%% normal use.

-spec format_error(term()) -> string().

format_error(macro_args) ->
    errormsg("macro call missing end parenthesis");
format_error({unknown, Reason}) ->
    errormsg(io_lib:format("unknown error: ~P", [Reason, 15])).

errormsg(String) ->
    io_lib:format("~s: ~s", [?MODULE, String]).


%% =====================================================================