1 package Devel::Declare;
2 # ABSTRACT: Adding keywords to perl, in perl
8 our $VERSION = '0.006017';
10 use constant DECLARE_NAME => 1;
11 use constant DECLARE_PROTO => 2;
12 use constant DECLARE_NONE => 4;
13 use constant DECLARE_PACKAGE => 8+1; # name implicit
15 use vars qw(%declarators %declarator_handlers @ISA);
16 use base qw(DynaLoader);
17 use Scalar::Util 'set_prototype';
18 use B::Hooks::OP::Check 0.19;
20 bootstrap Devel::Declare;
27 my ($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: $handlers";
291 Devel::Declare - Adding keywords to perl, in perl
295 use Method::Signatures;
300 # Use some new and exciting syntax like:
301 method hello (Str :$who, Int :$age where { $_ > 0 }) {
302 $self->say("Hello ${who}, I am ${age} years old!");
307 L<Devel::Declare> can install subroutines called declarators which locally take
308 over Perl's parser, allowing the creation of new syntax.
310 This document describes how to create a simple declarator.
314 We'll demonstrate the usage of C<Devel::Declare> with a motivating example: a new
315 C<method> keyword, which acts like the builtin C<sub>, but automatically unpacks
316 C<$self> and the other arguments.
321 =head2 Creating a declarator with C<setup_for>
323 You will typically create
329 Devel::Declare->setup_for(
331 { method => { const => \&parser } }
334 *{$caller.'::method'} = sub (&) {};
337 Starting from the end of this import routine, you'll see that we're creating a
338 subroutine called C<method> in the caller's namespace. Yes, that's just a normal
339 subroutine, and it does nothing at all (yet!) Note the prototype C<(&)> which means
340 that the caller would call it like so:
343 my ($self, $arg1, $arg2) = @_;
347 However we want to be able to call it like this
349 method foo ($arg1, $arg2) {
353 That's why we call C<setup_for> above, to register the declarator 'method' with a custom
354 parser, as per the next section. It acts on an optype, usually C<'const'> as above.
355 (Other valid values are C<'check'> and C<'rv2cv'>).
357 For a simpler way to install new methods, see also L<Devel::Declare::MethodInstaller::Simple>
359 =head2 Writing a parser subroutine
361 This subroutine is called at I<compilation> time, and allows you to read the custom
362 syntaxes that we want (in a syntax that may or may not be valid core Perl 5) and
363 munge it so that the result will be parsed by the C<perl> compiler.
365 For this example, we're defining some globals for convenience:
367 our ($Declarator, $Offset);
369 Then we define a parser subroutine to handle our declarator. We'll look at this in
373 local ($Declarator, $Offset) = @_;
375 C<Devel::Declare> provides some very low level utility methods to parse character
376 strings. We'll define some useful higher level routines below for convenience,
377 and we can use these to parse the various elements in our new syntax.
379 Notice how our parser subroutine is invoked at compile time,
380 when the C<perl> parser is pointed just I<before> the declarator name.
382 skip_declarator; # step past 'method'
383 my $name = strip_name; # strip out the name 'foo', if present
384 my $proto = strip_proto; # strip out the prototype '($arg1, $arg2)', if present
386 Now we can prepare some code to 'inject' into the new subroutine. For example we
387 might want the method as above to have C<my ($self, $arg1, $arg2) = @_> injected at
388 the beginning of it. We also do some clever stuff with scopes that we'll look
391 my $inject = make_proto_unwrap($proto);
393 $inject = scope_injector_call().$inject;
395 inject_if_block($inject);
397 We've now managed to change C<method ($arg1, $arg2) { ... }> into C<method {
398 injected_code; ... }>. This will compile... but we've lost the name of the
401 In a cute (or horrifying, depending on your perspective) trick, we temporarily
402 change the definition of the subroutine C<method> itself, to specialise it with
403 the C<$name> we stripped, so that it assigns the code block to that name.
405 Even though the I<next> time C<method> is compiled, it will be
406 redefined again, C<perl> caches these definitions in its parse
407 tree, so we'll always get the right one!
409 Note that we also handle the case where there was no name, allowing
410 an anonymous method analogous to an anonymous subroutine.
413 $name = join('::', Devel::Declare::get_curstash_name(), $name)
414 unless ($name =~ /::/);
415 shadow(sub (&) { no strict 'refs'; *{$name} = shift; });
417 shadow(sub (&) { shift });
422 =head2 Parser utilities in detail
424 For simplicity, we're using global variables like C<$Offset> in these examples.
425 You may prefer to look at L<Devel::Declare::Context::Simple>, which
426 encapsulates the context much more cleanly.
428 =head3 C<skip_declarator>
430 This simple parser just moves across a 'token'. The common case is
431 to skip the declarator, i.e. to move to the end of the string
432 'method' and before the prototype and code block.
434 sub skip_declarator {
435 $Offset += Devel::Declare::toke_move_past_token($Offset);
438 =head4 C<toke_move_past_token>
440 This builtin parser simply moves past a 'token' (matching C</[a-zA-Z_]\w*/>)
441 It takes an offset into the source document, and skips past the token.
442 It returns the number of characters skipped.
446 This parser skips any whitespace, then scans the next word (again matching a
447 'token'). We can then analyse the current line, and manipulate it (using pure
448 Perl). In this case we take the name of the method out, and return it.
452 if (my $len = Devel::Declare::toke_scan_word($Offset, 1)) {
453 my $linestr = Devel::Declare::get_linestr();
454 my $name = substr($linestr, $Offset, $len);
455 substr($linestr, $Offset, $len) = '';
456 Devel::Declare::set_linestr($linestr);
462 =head4 C<toke_scan_word>
464 This builtin parser, given an offset into the source document,
465 matches a 'token' as above but does not skip. It returns the
466 length of the token matched, if any.
468 =head4 C<get_linestr>
470 This builtin returns the full text of the current line of the source document.
472 =head4 C<set_linestr>
474 This builtin sets the full text of the current line of the source document.
475 Beware that injecting a newline into the middle of the line is likely
476 to fail in surprising ways. Generally, Perl's parser can rely on the
477 `current line' actually being only a single line. Use other kinds of
478 whitespace instead, in the code that you inject.
482 This parser skips whitsepace.
485 $Offset += Devel::Declare::toke_skipspace($Offset);
488 =head4 C<toke_skipspace>
490 This builtin parser, given an offset into the source document,
491 skips over any whitespace, and returns the number of characters
494 =head3 C<strip_proto>
496 This is a more complex parser that checks if it's found something that
497 starts with C<'('> and returns everything till the matching C<')'>.
502 my $linestr = Devel::Declare::get_linestr();
503 if (substr($linestr, $Offset, 1) eq '(') {
504 my $length = Devel::Declare::toke_scan_str($Offset);
505 my $proto = Devel::Declare::get_lex_stuff();
506 Devel::Declare::clear_lex_stuff();
507 $linestr = Devel::Declare::get_linestr();
508 substr($linestr, $Offset, $length) = '';
509 Devel::Declare::set_linestr($linestr);
515 =head4 C<toke_scan_str>
517 This builtin parser uses Perl's own parsing routines to match a "stringlike"
518 expression. Handily, this includes bracketed expressions (just think about
519 things like C<q(this is a quote)>).
521 Also it Does The Right Thing with nested delimiters (like C<q(this (is (a) quote))>).
523 It returns the effective length of the expression matched. Really, what
524 it returns is the difference in position between where the string started,
525 within the buffer, and where it finished. If the string extended across
526 multiple lines then the contents of the buffer may have been completely
527 replaced by the new lines, so this position difference is not the same
528 thing as the actual length of the expression matched. However, because
529 moving backward in the buffer causes problems, the function arranges
530 for the effective length to always be positive, padding the start of
531 the buffer if necessary.
533 Use C<get_lex_stuff> to get the actual matched text, the content of
534 the string. Because of the behaviour around multiline strings, you
535 can't reliably get this from the buffer. In fact, after the function
536 returns, you can't rely on any content of the buffer preceding the end
539 If the string being scanned is not well formed (has no closing delimiter),
540 C<toke_scan_str> returns C<undef>. In this case you cannot rely on the
541 contents of the buffer.
543 =head4 C<get_lex_stuff>
545 This builtin returns what was matched by C<toke_scan_str>. To avoid segfaults,
546 you should call C<clear_lex_stuff> immediately afterwards.
548 =head2 Munging the subroutine
550 Let's look at what we need to do in detail.
552 =head3 C<make_proto_unwrap>
554 We may have defined our method in different ways, which will result
555 in a different value for our prototype, as parsed above. For example:
557 method foo { # undefined
559 method foo ($arg1) { # '$arg1'
561 We deal with them as follows, and return the appropriate C<my ($self, ...) = @_;>
564 sub make_proto_unwrap {
566 my $inject = 'my ($self';
567 if (defined $proto) {
568 $inject .= ", $proto" if length($proto);
569 $inject .= ') = @_; ';
571 $inject .= ') = shift;';
576 =head3 C<inject_if_block>
578 Now we need to inject it after the opening C<'{'> of the method body.
579 We can do this with the building blocks we defined above like C<skipspace>
582 sub inject_if_block {
585 my $linestr = Devel::Declare::get_linestr;
586 if (substr($linestr, $Offset, 1) eq '{') {
587 substr($linestr, $Offset+1, 0) = $inject;
588 Devel::Declare::set_linestr($linestr);
592 =head3 C<scope_injector_call>
594 We want to be able to handle both named and anonymous methods. i.e.
596 method foo () { ... }
597 my $meth = method () { ... };
599 These will then get rewritten as
602 my $meth = method { ... };
604 where 'method' is a subroutine that takes a code block. Spot the problem?
605 The first one doesn't have a semicolon at the end of it! Unlike 'sub' which
606 is a builtin, this is just a normal statement, so we need to terminate it.
607 Luckily, using C<B::Hooks::EndOfScope>, we can do this!
609 use B::Hooks::EndOfScope;
611 We'll add this to what gets 'injected' at the beginning of the method source.
613 sub scope_injector_call {
614 return ' BEGIN { MethodHandlers::inject_scope }; ';
617 So at the beginning of every method, we are passing a callback that will get invoked
618 at the I<end> of the method's compilation... i.e. exactly then the closing C<'}'>
623 my $linestr = Devel::Declare::get_linestr;
624 my $offset = Devel::Declare::get_linestr_offset;
625 substr($linestr, $offset, 0) = ';';
626 Devel::Declare::set_linestr($linestr);
630 =head2 Shadowing each method.
634 We override the current definition of 'method' using C<shadow>.
637 my $pack = Devel::Declare::get_curstash_name;
638 Devel::Declare::shadow_sub("${pack}::${Declarator}", $_[0]);
641 For a named method we invoked like this:
643 shadow(sub (&) { no strict 'refs'; *{$name} = shift; });
645 So in the case of a C<method foo { ... }>, this call would redefine C<method>
646 to be a subroutine that exports 'sub foo' as the (munged) contents of C<{...}>.
648 The case of an anonymous method is also cute:
650 shadow(sub (&) { shift });
654 my $meth = method () { ... };
656 is rewritten with C<method> taking the codeblock, and returning it as is to become
657 the value of C<$meth>.
659 =head4 C<get_curstash_name>
661 This returns the package name I<currently being compiled>.
665 Handles the details of redefining the subroutine.
669 One of the best ways to learn C<Devel::Declare> is still to look at
672 L<http://cpants.perl.org/dist/used_by/Devel-Declare>.
676 Matt S Trout - E<lt>mst@shadowcat.co.ukE<gt> - original author
678 Company: http://www.shadowcat.co.uk/
679 Blog: http://chainsawblues.vox.com/
681 Florian Ragwitz E<lt>rafl@debian.orgE<gt> - maintainer
683 osfameron E<lt>osfameron@cpan.orgE<gt> - first draft of documentation
685 =head1 COPYRIGHT AND LICENSE
687 This library is free software under the same terms as perl itself
689 Copyright (c) 2007, 2008, 2009 Matt S Trout
691 Copyright (c) 2008, 2009 Florian Ragwitz
693 stolen_chunk_of_toke.c based on toke.c from the perl core, which is
695 Copyright (C) 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999,
696 2000, 2001, 2002, 2003, 2004, 2005, 2006, by Larry Wall and others