1 package Devel::Declare;
7 our $VERSION = '0.006022';
9 bootstrap Devel::Declare;
12 use constant DECLARE_NAME => 1;
13 use constant DECLARE_PROTO => 2;
14 use constant DECLARE_NONE => 4;
15 use constant DECLARE_PACKAGE => 8+1; # name implicit
17 our (%declarators, %declarator_handlers, @ISA);
18 use base qw(DynaLoader);
19 use Scalar::Util 'set_prototype';
20 use B::Hooks::OP::Check 0.19;
27 my ($class, %args) = @_;
29 if (@_ == 1) { # "use Devel::Declare;"
31 foreach my $name (qw(NAME PROTO NONE PACKAGE)) {
32 *{"${target}::DECLARE_${name}"} = *{"DECLARE_${name}"};
35 $class->setup_for($target => \%args);
42 $class->teardown_for($target);
46 my ($class, $target, $args) = @_;
48 foreach my $key (keys %$args) {
49 my $info = $args->{$key};
51 if (ref($info) eq 'ARRAY') {
52 ($flags, $sub) = @$info;
53 } elsif (ref($info) eq 'CODE') {
54 $flags = DECLARE_NAME;
56 } elsif (ref($info) eq 'HASH') {
60 die "Info for sub ${key} must be [ \$flags, \$sub ] or \$sub or handler hashref";
62 $declarators{$target}{$key} = $flags;
63 $declarator_handlers{$target}{$key} = $sub;
68 my ($class, $target) = @_;
69 delete $declarators{$target};
70 delete $declarator_handlers{$target};
77 my ($usepack, $use, $inpack, $name, $proto, $traits) = @_;
78 my ($name_h, $XX_h, $extra_code)
79 = $declarator_handlers{$usepack}{$use}->(
80 $usepack, $use, $inpack, $name, $proto, defined(wantarray), $traits
82 ($temp_name, $temp_save) = ([], []);
84 $name = "${inpack}::${name}" unless $name =~ /::/;
85 shadow_sub($name, $name_h);
88 shadow_sub("${inpack}::X", $XX_h);
90 if (defined wantarray) {
91 return $extra_code || '0;';
99 push(@$temp_name, $name);
101 my ($pack, $pname) = ($name =~ m/(.+)::([^:]+)/);
102 push(@$temp_save, $pack->can($pname));
103 no warnings 'redefine';
104 no warnings 'prototype';
106 set_in_declare(~~@{$temp_name||[]});
111 my $name = shift(@{$temp_name||[]});
112 die "done_declare called with no temp_name stack" unless defined($name);
113 my $saved = shift(@$temp_save);
116 delete ${"${temp_pack}::"}{$name};
118 no warnings 'prototype';
119 *{"${temp_pack}::${name}"} = $saved;
121 set_in_declare(~~@{$temp_name||[]});
124 sub build_sub_installer {
125 my ($class, $pack, $name, $proto) = @_;
129 sub ${name} (${proto}) :lvalue {\n"
133 my $ret = $body->(@_);
136 sub { ($body) = @_; };';
139 sub setup_declarators {
140 my ($class, $pack, $to_setup) = @_;
141 die "${class}->setup_declarators(\$pack, \\\%to_setup)"
142 unless defined($pack) && ref($to_setup) eq 'HASH';
144 foreach my $name (keys %$to_setup) {
145 my $info = $to_setup->{$name};
146 my $flags = $info->{flags} || DECLARE_NAME;
147 my $run = $info->{run};
148 my $compile = $info->{compile};
149 my $proto = $info->{proto} || '&';
150 my $sub_proto = $proto;
151 # make all args optional to enable lvalue for DECLARE_NONE
152 $sub_proto =~ s/;//; $sub_proto = ';'.$sub_proto;
153 #my $installer = $class->build_sub_installer($pack, $name, $proto);
154 my $installer = $class->build_sub_installer($pack, $name, '@');
155 $installer->(sub :lvalue {
156 #{ no warnings 'uninitialized'; warn 'INST: '.join(', ', @_)."\n"; }
158 if (ref $_[0] eq 'HASH') {
161 my @ret = $run->(undef, undef, @_);
164 my $r = $run->(undef, undef, @_);
172 $setup_for_args{$name} = [
175 my ($usepack, $use, $inpack, $name, $proto, $shift_hashref, $traits) = @_;
176 my $extra_code = $compile->($name, $proto, $traits);
177 my $main_handler = sub { shift if $shift_hashref;
178 ("DONE", $run->($name, $proto, @_));
181 if (defined $proto) {
182 $name_h = sub :lvalue { return my $sv; };
184 } elsif (defined $name && length $name) {
185 $name_h = $main_handler;
188 $extra_code = '}, sub {'.$extra_code;
189 return ($name_h, $XX, $extra_code);
193 $class->setup_for($pack, \%setup_for_args);
196 sub install_declarator {
197 my ($class, $target_pack, $target_name, $flags, $filter, $handler) = @_;
198 $class->setup_declarators($target_pack, {
207 sub linestr_callback_rv2cv {
208 my ($name, $offset) = @_;
209 $offset += toke_move_past_token($offset);
210 my $pack = get_curstash_name();
211 my $flags = $declarators{$pack}{$name};
212 my ($found_name, $found_proto);
213 if ($flags & DECLARE_NAME) {
214 $offset += toke_skipspace($offset);
215 my $linestr = get_linestr();
216 if (substr($linestr, $offset, 2) eq '::') {
217 substr($linestr, $offset, 2) = '';
218 set_linestr($linestr);
220 if (my $len = toke_scan_word($offset, $flags & DECLARE_PACKAGE)) {
221 $found_name = substr($linestr, $offset, $len);
225 if ($flags & DECLARE_PROTO) {
226 $offset += toke_skipspace($offset);
227 my $linestr = get_linestr();
228 if (substr($linestr, $offset, 1) eq '(') {
229 my $length = toke_scan_str($offset);
230 $found_proto = get_lex_stuff();
233 ($found_name ? ' ' : '=')
234 .'X'.(' ' x length($found_proto));
235 $linestr = get_linestr();
236 substr($linestr, $offset, $length) = $replace;
237 set_linestr($linestr);
241 my @args = ($pack, $name, $pack, $found_name, $found_proto);
242 $offset += toke_skipspace($offset);
243 my $linestr = get_linestr();
244 if (substr($linestr, $offset, 1) eq '{') {
245 my $ret = init_declare(@args);
247 if (defined $ret && length $ret) {
248 substr($linestr, $offset, 0) = $ret;
249 set_linestr($linestr);
254 #warn "linestr now ${linestr}";
257 sub linestr_callback_const {
258 my ($name, $offset) = @_;
259 my $pack = get_curstash_name();
260 my $flags = $declarators{$pack}{$name};
261 if ($flags & DECLARE_NAME) {
262 $offset += toke_move_past_token($offset);
263 $offset += toke_skipspace($offset);
264 if (toke_scan_word($offset, $flags & DECLARE_PACKAGE)) {
265 my $linestr = get_linestr();
266 substr($linestr, $offset, 0) = '::';
267 set_linestr($linestr);
272 sub linestr_callback {
275 my $pack = get_curstash_name();
276 my $handlers = $declarator_handlers{$pack}{$name};
277 if (ref $handlers eq 'CODE') {
278 my $meth = "linestr_callback_${type}";
279 __PACKAGE__->can($meth)->(@_);
280 } elsif (ref $handlers eq 'HASH') {
281 if ($handlers->{$type}) {
282 $handlers->{$type}->(@_);
285 die "PANIC: unknown thing in handlers for $pack $name: $handlers";
291 Devel::Declare - (DEPRECATED) Adding keywords to perl, in perl
295 use Method::Signatures;
300 # Use some new and exciting syntax like:
301 method hello (Str :$who, Int :$age where { $_ > 0 }) {
302 $self->say("Hello ${who}, I am ${age} years old!");
307 L<Devel::Declare> can install subroutines called declarators which locally take
308 over Perl's parser, allowing the creation of new syntax.
310 This document describes how to create a simple declarator.
314 =for comment mst wrote this warning for MooseX::Declare, and ether adapted it for here:
316 B<Warning:> Devel::Declare is a giant bag of crack
317 originally implemented by mst with the goal of upsetting the perl core
318 developers so much by its very existence that they implemented proper
319 keyword handling in the core.
321 As of perl5 version 14, this goal has been achieved, and modules such
322 as L<Devel::CallParser>, L<Function::Parameters>, and L<Keyword::Simple> provide
323 mechanisms to mangle perl syntax that don't require hallucinogenic
324 drugs to interpret the error messages they produce.
326 If you are using something that uses Devel::Declare, please for the love
327 of kittens use something else:
333 Instead of L<TryCatch>, use L<Syntax::Keyword::Try> or L<Try::Tiny>
337 Instead of L<Method::Signatures>, use
338 L<real subroutine signatures|perlsub/Signatures> (requires perl 5.22) or L<Moops>
342 If you are a maintainer of something that uses Devel::Declare itself, please take a look at the
343 more modern and robust alternatives, such as L<Keyword::Declare>, L<Keyword::Simple> or using
344 L<perlapi/PL_keyword_plugin> in XS directly.
348 We'll demonstrate the usage of C<Devel::Declare> with a motivating example: a new
349 C<method> keyword, which acts like the builtin C<sub>, but automatically unpacks
350 C<$self> and the other arguments.
355 =head2 Creating a declarator with C<setup_for>
357 You will typically create
363 Devel::Declare->setup_for(
365 { method => { const => \&parser } }
368 *{$caller.'::method'} = sub (&) {};
371 Starting from the end of this import routine, you'll see that we're creating a
372 subroutine called C<method> in the caller's namespace. Yes, that's just a normal
373 subroutine, and it does nothing at all (yet!) Note the prototype C<(&)> which means
374 that the caller would call it like so:
377 my ($self, $arg1, $arg2) = @_;
381 However we want to be able to call it like this
383 method foo ($arg1, $arg2) {
387 That's why we call C<setup_for> above, to register the declarator 'method' with a custom
388 parser, as per the next section. It acts on an optype, usually C<'const'> as above.
389 (Other valid values are C<'check'> and C<'rv2cv'>).
391 For a simpler way to install new methods, see also L<Devel::Declare::MethodInstaller::Simple>
393 =head2 Writing a parser subroutine
395 This subroutine is called at I<compilation> time, and allows you to read the custom
396 syntaxes that we want (in a syntax that may or may not be valid core Perl 5) and
397 munge it so that the result will be parsed by the C<perl> compiler.
399 For this example, we're defining some globals for convenience:
401 our ($Declarator, $Offset);
403 Then we define a parser subroutine to handle our declarator. We'll look at this in
407 local ($Declarator, $Offset) = @_;
409 C<Devel::Declare> provides some very low level utility methods to parse character
410 strings. We'll define some useful higher level routines below for convenience,
411 and we can use these to parse the various elements in our new syntax.
413 Notice how our parser subroutine is invoked at compile time,
414 when the C<perl> parser is pointed just I<before> the declarator name.
416 skip_declarator; # step past 'method'
417 my $name = strip_name; # strip out the name 'foo', if present
418 my $proto = strip_proto; # strip out the prototype '($arg1, $arg2)', if present
420 Now we can prepare some code to 'inject' into the new subroutine. For example we
421 might want the method as above to have C<my ($self, $arg1, $arg2) = @_> injected at
422 the beginning of it. We also do some clever stuff with scopes that we'll look
425 my $inject = make_proto_unwrap($proto);
427 $inject = scope_injector_call().$inject;
429 inject_if_block($inject);
431 We've now managed to change C<method ($arg1, $arg2) { ... }> into C<method {
432 injected_code; ... }>. This will compile... but we've lost the name of the
435 In a cute (or horrifying, depending on your perspective) trick, we temporarily
436 change the definition of the subroutine C<method> itself, to specialise it with
437 the C<$name> we stripped, so that it assigns the code block to that name.
439 Even though the I<next> time C<method> is compiled, it will be
440 redefined again, C<perl> caches these definitions in its parse
441 tree, so we'll always get the right one!
443 Note that we also handle the case where there was no name, allowing
444 an anonymous method analogous to an anonymous subroutine.
447 $name = join('::', Devel::Declare::get_curstash_name(), $name)
448 unless ($name =~ /::/);
449 shadow(sub (&) { no strict 'refs'; *{$name} = shift; });
451 shadow(sub (&) { shift });
456 =head2 Parser utilities in detail
458 For simplicity, we're using global variables like C<$Offset> in these examples.
459 You may prefer to look at L<Devel::Declare::Context::Simple>, which
460 encapsulates the context much more cleanly.
462 =head3 C<skip_declarator>
464 This simple parser just moves across a 'token'. The common case is
465 to skip the declarator, i.e. to move to the end of the string
466 'method' and before the prototype and code block.
468 sub skip_declarator {
469 $Offset += Devel::Declare::toke_move_past_token($Offset);
472 =head4 C<toke_move_past_token>
474 This builtin parser simply moves past a 'token' (matching C</[a-zA-Z_]\w*/>)
475 It takes an offset into the source document, and skips past the token.
476 It returns the number of characters skipped.
480 This parser skips any whitespace, then scans the next word (again matching a
481 'token'). We can then analyse the current line, and manipulate it (using pure
482 Perl). In this case we take the name of the method out, and return it.
486 if (my $len = Devel::Declare::toke_scan_word($Offset, 1)) {
487 my $linestr = Devel::Declare::get_linestr();
488 my $name = substr($linestr, $Offset, $len);
489 substr($linestr, $Offset, $len) = '';
490 Devel::Declare::set_linestr($linestr);
496 =head4 C<toke_scan_word>
498 This builtin parser, given an offset into the source document,
499 matches a 'token' as above but does not skip. It returns the
500 length of the token matched, if any.
502 =head4 C<get_linestr>
504 This builtin returns the full text of the current line of the source document.
506 =head4 C<set_linestr>
508 This builtin sets the full text of the current line of the source document.
509 Beware that injecting a newline into the middle of the line is likely
510 to fail in surprising ways. Generally, Perl's parser can rely on the
511 `current line' actually being only a single line. Use other kinds of
512 whitespace instead, in the code that you inject.
516 This parser skips whitsepace.
519 $Offset += Devel::Declare::toke_skipspace($Offset);
522 =head4 C<toke_skipspace>
524 This builtin parser, given an offset into the source document,
525 skips over any whitespace, and returns the number of characters
528 =head3 C<strip_proto>
530 This is a more complex parser that checks if it's found something that
531 starts with C<'('> and returns everything till the matching C<')'>.
536 my $linestr = Devel::Declare::get_linestr();
537 if (substr($linestr, $Offset, 1) eq '(') {
538 my $length = Devel::Declare::toke_scan_str($Offset);
539 my $proto = Devel::Declare::get_lex_stuff();
540 Devel::Declare::clear_lex_stuff();
541 $linestr = Devel::Declare::get_linestr();
542 substr($linestr, $Offset, $length) = '';
543 Devel::Declare::set_linestr($linestr);
549 =head4 C<toke_scan_str>
551 This builtin parser uses Perl's own parsing routines to match a "stringlike"
552 expression. Handily, this includes bracketed expressions (just think about
553 things like C<q(this is a quote)>).
555 Also it Does The Right Thing with nested delimiters (like C<q(this (is (a) quote))>).
557 It returns the effective length of the expression matched. Really, what
558 it returns is the difference in position between where the string started,
559 within the buffer, and where it finished. If the string extended across
560 multiple lines then the contents of the buffer may have been completely
561 replaced by the new lines, so this position difference is not the same
562 thing as the actual length of the expression matched. However, because
563 moving backward in the buffer causes problems, the function arranges
564 for the effective length to always be positive, padding the start of
565 the buffer if necessary.
567 Use C<get_lex_stuff> to get the actual matched text, the content of
568 the string. Because of the behaviour around multiline strings, you
569 can't reliably get this from the buffer. In fact, after the function
570 returns, you can't rely on any content of the buffer preceding the end
573 If the string being scanned is not well formed (has no closing delimiter),
574 C<toke_scan_str> returns C<undef>. In this case you cannot rely on the
575 contents of the buffer.
577 =head4 C<get_lex_stuff>
579 This builtin returns what was matched by C<toke_scan_str>. To avoid segfaults,
580 you should call C<clear_lex_stuff> immediately afterwards.
582 =head2 Munging the subroutine
584 Let's look at what we need to do in detail.
586 =head3 C<make_proto_unwrap>
588 We may have defined our method in different ways, which will result
589 in a different value for our prototype, as parsed above. For example:
591 method foo { # undefined
593 method foo ($arg1) { # '$arg1'
595 We deal with them as follows, and return the appropriate C<my ($self, ...) = @_;>
598 sub make_proto_unwrap {
600 my $inject = 'my ($self';
601 if (defined $proto) {
602 $inject .= ", $proto" if length($proto);
603 $inject .= ') = @_; ';
605 $inject .= ') = shift;';
610 =head3 C<inject_if_block>
612 Now we need to inject it after the opening C<'{'> of the method body.
613 We can do this with the building blocks we defined above like C<skipspace>
616 sub inject_if_block {
619 my $linestr = Devel::Declare::get_linestr;
620 if (substr($linestr, $Offset, 1) eq '{') {
621 substr($linestr, $Offset+1, 0) = $inject;
622 Devel::Declare::set_linestr($linestr);
626 =head3 C<scope_injector_call>
628 We want to be able to handle both named and anonymous methods. i.e.
630 method foo () { ... }
631 my $meth = method () { ... };
633 These will then get rewritten as
636 my $meth = method { ... };
638 where 'method' is a subroutine that takes a code block. Spot the problem?
639 The first one doesn't have a semicolon at the end of it! Unlike 'sub' which
640 is a builtin, this is just a normal statement, so we need to terminate it.
641 Luckily, using C<B::Hooks::EndOfScope>, we can do this!
643 use B::Hooks::EndOfScope;
645 We'll add this to what gets 'injected' at the beginning of the method source.
647 sub scope_injector_call {
648 return ' BEGIN { MethodHandlers::inject_scope }; ';
651 So at the beginning of every method, we are passing a callback that will get invoked
652 at the I<end> of the method's compilation... i.e. exactly then the closing C<'}'>
657 my $linestr = Devel::Declare::get_linestr;
658 my $offset = Devel::Declare::get_linestr_offset;
659 substr($linestr, $offset, 0) = ';';
660 Devel::Declare::set_linestr($linestr);
664 =head2 Shadowing each method.
668 We override the current definition of 'method' using C<shadow>.
671 my $pack = Devel::Declare::get_curstash_name;
672 Devel::Declare::shadow_sub("${pack}::${Declarator}", $_[0]);
675 For a named method we invoked like this:
677 shadow(sub (&) { no strict 'refs'; *{$name} = shift; });
679 So in the case of a C<method foo { ... }>, this call would redefine C<method>
680 to be a subroutine that exports 'sub foo' as the (munged) contents of C<{...}>.
682 The case of an anonymous method is also cute:
684 shadow(sub (&) { shift });
688 my $meth = method () { ... };
690 is rewritten with C<method> taking the codeblock, and returning it as is to become
691 the value of C<$meth>.
693 =head4 C<get_curstash_name>
695 This returns the package name I<currently being compiled>.
699 Handles the details of redefining the subroutine.
703 One of the best ways to learn C<Devel::Declare> is still to look at
706 L<http://cpants.perl.org/dist/used_by/Devel-Declare>.
710 Matt S Trout - E<lt>mst@shadowcat.co.ukE<gt> - original author
712 Company: http://www.shadowcat.co.uk/
713 Blog: http://chainsawblues.vox.com/
715 Florian Ragwitz E<lt>rafl@debian.orgE<gt> - maintainer
717 osfameron E<lt>osfameron@cpan.orgE<gt> - first draft of documentation
719 =head1 COPYRIGHT AND LICENSE
721 This library is free software under the same terms as perl itself
723 Copyright (c) 2007, 2008, 2009 Matt S Trout
725 Copyright (c) 2008, 2009 Florian Ragwitz
727 stolen_chunk_of_toke.c based on toke.c from the perl core, which is
729 Copyright (C) 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999,
730 2000, 2001, 2002, 2003, 2004, 2005, 2006, by Larry Wall and others