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 ${age} years old!");
307 L<Devel::Declare> can install subroutines called declarators which locally take
308 over Perl's parser, allowing the creation of new syntax.
310 This document describes how to create a simple declarator.
314 =for comment mst wrote this warning for MooseX::Declare, and ether adapted it for here:
316 B<Warning:> Devel::Declare is a giant bag of crack
317 originally implemented by mst with the goal of upsetting the perl core
318 developers so much by its very existence that they implemented proper
319 keyword handling in the core.
321 As of perl5 version 14, this goal has been achieved, and modules such
322 as L<Devel::CallParser>, L<Function::Parameters>, and L<Keyword::Simple> provide
323 mechanisms to mangle perl syntax that don't require hallucinogenic
324 drugs to interpret the error messages they produce.
326 If you are using something that uses Devel::Declare, please for the love
327 of kittens use something else:
333 Instead of L<TryCatch>, use L<Try::Tiny>
337 Instead of L<Method::Signatures>, use
338 L<real subroutine signatures|perlsub/Signatures> (requires perl 5.22) or L<Moops>
344 We'll demonstrate the usage of C<Devel::Declare> with a motivating example: a new
345 C<method> keyword, which acts like the builtin C<sub>, but automatically unpacks
346 C<$self> and the other arguments.
351 =head2 Creating a declarator with C<setup_for>
353 You will typically create
359 Devel::Declare->setup_for(
361 { method => { const => \&parser } }
364 *{$caller.'::method'} = sub (&) {};
367 Starting from the end of this import routine, you'll see that we're creating a
368 subroutine called C<method> in the caller's namespace. Yes, that's just a normal
369 subroutine, and it does nothing at all (yet!) Note the prototype C<(&)> which means
370 that the caller would call it like so:
373 my ($self, $arg1, $arg2) = @_;
377 However we want to be able to call it like this
379 method foo ($arg1, $arg2) {
383 That's why we call C<setup_for> above, to register the declarator 'method' with a custom
384 parser, as per the next section. It acts on an optype, usually C<'const'> as above.
385 (Other valid values are C<'check'> and C<'rv2cv'>).
387 For a simpler way to install new methods, see also L<Devel::Declare::MethodInstaller::Simple>
389 =head2 Writing a parser subroutine
391 This subroutine is called at I<compilation> time, and allows you to read the custom
392 syntaxes that we want (in a syntax that may or may not be valid core Perl 5) and
393 munge it so that the result will be parsed by the C<perl> compiler.
395 For this example, we're defining some globals for convenience:
397 our ($Declarator, $Offset);
399 Then we define a parser subroutine to handle our declarator. We'll look at this in
403 local ($Declarator, $Offset) = @_;
405 C<Devel::Declare> provides some very low level utility methods to parse character
406 strings. We'll define some useful higher level routines below for convenience,
407 and we can use these to parse the various elements in our new syntax.
409 Notice how our parser subroutine is invoked at compile time,
410 when the C<perl> parser is pointed just I<before> the declarator name.
412 skip_declarator; # step past 'method'
413 my $name = strip_name; # strip out the name 'foo', if present
414 my $proto = strip_proto; # strip out the prototype '($arg1, $arg2)', if present
416 Now we can prepare some code to 'inject' into the new subroutine. For example we
417 might want the method as above to have C<my ($self, $arg1, $arg2) = @_> injected at
418 the beginning of it. We also do some clever stuff with scopes that we'll look
421 my $inject = make_proto_unwrap($proto);
423 $inject = scope_injector_call().$inject;
425 inject_if_block($inject);
427 We've now managed to change C<method ($arg1, $arg2) { ... }> into C<method {
428 injected_code; ... }>. This will compile... but we've lost the name of the
431 In a cute (or horrifying, depending on your perspective) trick, we temporarily
432 change the definition of the subroutine C<method> itself, to specialise it with
433 the C<$name> we stripped, so that it assigns the code block to that name.
435 Even though the I<next> time C<method> is compiled, it will be
436 redefined again, C<perl> caches these definitions in its parse
437 tree, so we'll always get the right one!
439 Note that we also handle the case where there was no name, allowing
440 an anonymous method analogous to an anonymous subroutine.
443 $name = join('::', Devel::Declare::get_curstash_name(), $name)
444 unless ($name =~ /::/);
445 shadow(sub (&) { no strict 'refs'; *{$name} = shift; });
447 shadow(sub (&) { shift });
452 =head2 Parser utilities in detail
454 For simplicity, we're using global variables like C<$Offset> in these examples.
455 You may prefer to look at L<Devel::Declare::Context::Simple>, which
456 encapsulates the context much more cleanly.
458 =head3 C<skip_declarator>
460 This simple parser just moves across a 'token'. The common case is
461 to skip the declarator, i.e. to move to the end of the string
462 'method' and before the prototype and code block.
464 sub skip_declarator {
465 $Offset += Devel::Declare::toke_move_past_token($Offset);
468 =head4 C<toke_move_past_token>
470 This builtin parser simply moves past a 'token' (matching C</[a-zA-Z_]\w*/>)
471 It takes an offset into the source document, and skips past the token.
472 It returns the number of characters skipped.
476 This parser skips any whitespace, then scans the next word (again matching a
477 'token'). We can then analyse the current line, and manipulate it (using pure
478 Perl). In this case we take the name of the method out, and return it.
482 if (my $len = Devel::Declare::toke_scan_word($Offset, 1)) {
483 my $linestr = Devel::Declare::get_linestr();
484 my $name = substr($linestr, $Offset, $len);
485 substr($linestr, $Offset, $len) = '';
486 Devel::Declare::set_linestr($linestr);
492 =head4 C<toke_scan_word>
494 This builtin parser, given an offset into the source document,
495 matches a 'token' as above but does not skip. It returns the
496 length of the token matched, if any.
498 =head4 C<get_linestr>
500 This builtin returns the full text of the current line of the source document.
502 =head4 C<set_linestr>
504 This builtin sets the full text of the current line of the source document.
505 Beware that injecting a newline into the middle of the line is likely
506 to fail in surprising ways. Generally, Perl's parser can rely on the
507 `current line' actually being only a single line. Use other kinds of
508 whitespace instead, in the code that you inject.
512 This parser skips whitsepace.
515 $Offset += Devel::Declare::toke_skipspace($Offset);
518 =head4 C<toke_skipspace>
520 This builtin parser, given an offset into the source document,
521 skips over any whitespace, and returns the number of characters
524 =head3 C<strip_proto>
526 This is a more complex parser that checks if it's found something that
527 starts with C<'('> and returns everything till the matching C<')'>.
532 my $linestr = Devel::Declare::get_linestr();
533 if (substr($linestr, $Offset, 1) eq '(') {
534 my $length = Devel::Declare::toke_scan_str($Offset);
535 my $proto = Devel::Declare::get_lex_stuff();
536 Devel::Declare::clear_lex_stuff();
537 $linestr = Devel::Declare::get_linestr();
538 substr($linestr, $Offset, $length) = '';
539 Devel::Declare::set_linestr($linestr);
545 =head4 C<toke_scan_str>
547 This builtin parser uses Perl's own parsing routines to match a "stringlike"
548 expression. Handily, this includes bracketed expressions (just think about
549 things like C<q(this is a quote)>).
551 Also it Does The Right Thing with nested delimiters (like C<q(this (is (a) quote))>).
553 It returns the effective length of the expression matched. Really, what
554 it returns is the difference in position between where the string started,
555 within the buffer, and where it finished. If the string extended across
556 multiple lines then the contents of the buffer may have been completely
557 replaced by the new lines, so this position difference is not the same
558 thing as the actual length of the expression matched. However, because
559 moving backward in the buffer causes problems, the function arranges
560 for the effective length to always be positive, padding the start of
561 the buffer if necessary.
563 Use C<get_lex_stuff> to get the actual matched text, the content of
564 the string. Because of the behaviour around multiline strings, you
565 can't reliably get this from the buffer. In fact, after the function
566 returns, you can't rely on any content of the buffer preceding the end
569 If the string being scanned is not well formed (has no closing delimiter),
570 C<toke_scan_str> returns C<undef>. In this case you cannot rely on the
571 contents of the buffer.
573 =head4 C<get_lex_stuff>
575 This builtin returns what was matched by C<toke_scan_str>. To avoid segfaults,
576 you should call C<clear_lex_stuff> immediately afterwards.
578 =head2 Munging the subroutine
580 Let's look at what we need to do in detail.
582 =head3 C<make_proto_unwrap>
584 We may have defined our method in different ways, which will result
585 in a different value for our prototype, as parsed above. For example:
587 method foo { # undefined
589 method foo ($arg1) { # '$arg1'
591 We deal with them as follows, and return the appropriate C<my ($self, ...) = @_;>
594 sub make_proto_unwrap {
596 my $inject = 'my ($self';
597 if (defined $proto) {
598 $inject .= ", $proto" if length($proto);
599 $inject .= ') = @_; ';
601 $inject .= ') = shift;';
606 =head3 C<inject_if_block>
608 Now we need to inject it after the opening C<'{'> of the method body.
609 We can do this with the building blocks we defined above like C<skipspace>
612 sub inject_if_block {
615 my $linestr = Devel::Declare::get_linestr;
616 if (substr($linestr, $Offset, 1) eq '{') {
617 substr($linestr, $Offset+1, 0) = $inject;
618 Devel::Declare::set_linestr($linestr);
622 =head3 C<scope_injector_call>
624 We want to be able to handle both named and anonymous methods. i.e.
626 method foo () { ... }
627 my $meth = method () { ... };
629 These will then get rewritten as
632 my $meth = method { ... };
634 where 'method' is a subroutine that takes a code block. Spot the problem?
635 The first one doesn't have a semicolon at the end of it! Unlike 'sub' which
636 is a builtin, this is just a normal statement, so we need to terminate it.
637 Luckily, using C<B::Hooks::EndOfScope>, we can do this!
639 use B::Hooks::EndOfScope;
641 We'll add this to what gets 'injected' at the beginning of the method source.
643 sub scope_injector_call {
644 return ' BEGIN { MethodHandlers::inject_scope }; ';
647 So at the beginning of every method, we are passing a callback that will get invoked
648 at the I<end> of the method's compilation... i.e. exactly then the closing C<'}'>
653 my $linestr = Devel::Declare::get_linestr;
654 my $offset = Devel::Declare::get_linestr_offset;
655 substr($linestr, $offset, 0) = ';';
656 Devel::Declare::set_linestr($linestr);
660 =head2 Shadowing each method.
664 We override the current definition of 'method' using C<shadow>.
667 my $pack = Devel::Declare::get_curstash_name;
668 Devel::Declare::shadow_sub("${pack}::${Declarator}", $_[0]);
671 For a named method we invoked like this:
673 shadow(sub (&) { no strict 'refs'; *{$name} = shift; });
675 So in the case of a C<method foo { ... }>, this call would redefine C<method>
676 to be a subroutine that exports 'sub foo' as the (munged) contents of C<{...}>.
678 The case of an anonymous method is also cute:
680 shadow(sub (&) { shift });
684 my $meth = method () { ... };
686 is rewritten with C<method> taking the codeblock, and returning it as is to become
687 the value of C<$meth>.
689 =head4 C<get_curstash_name>
691 This returns the package name I<currently being compiled>.
695 Handles the details of redefining the subroutine.
699 One of the best ways to learn C<Devel::Declare> is still to look at
702 L<http://cpants.perl.org/dist/used_by/Devel-Declare>.
706 Matt S Trout - E<lt>mst@shadowcat.co.ukE<gt> - original author
708 Company: http://www.shadowcat.co.uk/
709 Blog: http://chainsawblues.vox.com/
711 Florian Ragwitz E<lt>rafl@debian.orgE<gt> - maintainer
713 osfameron E<lt>osfameron@cpan.orgE<gt> - first draft of documentation
715 =head1 COPYRIGHT AND LICENSE
717 This library is free software under the same terms as perl itself
719 Copyright (c) 2007, 2008, 2009 Matt S Trout
721 Copyright (c) 2008, 2009 Florian Ragwitz
723 stolen_chunk_of_toke.c based on toke.c from the perl core, which is
725 Copyright (C) 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999,
726 2000, 2001, 2002, 2003, 2004, 2005, 2006, by Larry Wall and others