1 package Devel::Declare;
7 our $VERSION = '0.006007';
9 use constant DECLARE_NAME => 1;
10 use constant DECLARE_PROTO => 2;
11 use constant DECLARE_NONE => 4;
12 use constant DECLARE_PACKAGE => 8+1; # name implicit
14 use vars qw(%declarators %declarator_handlers @ISA);
15 use base qw(DynaLoader);
16 use Scalar::Util 'set_prototype';
17 use B::Hooks::OP::Check 0.19;
19 bootstrap Devel::Declare;
26 my ($class, %args) = @_;
28 if (@_ == 1) { # "use Devel::Declare;"
30 foreach my $name (qw(NAME PROTO NONE PACKAGE)) {
31 *{"${target}::DECLARE_${name}"} = *{"DECLARE_${name}"};
34 $class->setup_for($target => \%args);
41 $class->teardown_for($target);
45 my ($class, $target, $args) = @_;
47 foreach my $key (keys %$args) {
48 my $info = $args->{$key};
50 if (ref($info) eq 'ARRAY') {
51 ($flags, $sub) = @$info;
52 } elsif (ref($info) eq 'CODE') {
53 $flags = DECLARE_NAME;
55 } elsif (ref($info) eq 'HASH') {
59 die "Info for sub ${key} must be [ \$flags, \$sub ] or \$sub or handler hashref";
61 $declarators{$target}{$key} = $flags;
62 $declarator_handlers{$target}{$key} = $sub;
67 my ($class, $target) = @_;
68 delete $declarators{$target};
69 delete $declarator_handlers{$target};
76 my ($usepack, $use, $inpack, $name, $proto, $traits) = @_;
77 my ($name_h, $XX_h, $extra_code)
78 = $declarator_handlers{$usepack}{$use}->(
79 $usepack, $use, $inpack, $name, $proto, defined(wantarray), $traits
81 ($temp_name, $temp_save) = ([], []);
83 $name = "${inpack}::${name}" unless $name =~ /::/;
84 shadow_sub($name, $name_h);
87 shadow_sub("${inpack}::X", $XX_h);
89 if (defined wantarray) {
90 return $extra_code || '0;';
98 push(@$temp_name, $name);
100 my ($pack, $pname) = ($name =~ m/(.+)::([^:]+)/);
101 push(@$temp_save, $pack->can($pname));
102 no warnings 'redefine';
103 no warnings 'prototype';
105 set_in_declare(~~@{$temp_name||[]});
110 my $name = shift(@{$temp_name||[]});
111 die "done_declare called with no temp_name stack" unless defined($name);
112 my $saved = shift(@$temp_save);
115 delete ${"${temp_pack}::"}{$name};
117 no warnings 'prototype';
118 *{"${temp_pack}::${name}"} = $saved;
120 set_in_declare(~~@{$temp_name||[]});
123 sub build_sub_installer {
124 my ($class, $pack, $name, $proto) = @_;
128 sub ${name} (${proto}) :lvalue {\n"
132 my $ret = $body->(@_);
135 sub { ($body) = @_; };';
138 sub setup_declarators {
139 my ($class, $pack, $to_setup) = @_;
140 die "${class}->setup_declarators(\$pack, \\\%to_setup)"
141 unless defined($pack) && ref($to_setup) eq 'HASH';
143 foreach my $name (keys %$to_setup) {
144 my $info = $to_setup->{$name};
145 my $flags = $info->{flags} || DECLARE_NAME;
146 my $run = $info->{run};
147 my $compile = $info->{compile};
148 my $proto = $info->{proto} || '&';
149 my $sub_proto = $proto;
150 # make all args optional to enable lvalue for DECLARE_NONE
151 $sub_proto =~ s/;//; $sub_proto = ';'.$sub_proto;
152 #my $installer = $class->build_sub_installer($pack, $name, $proto);
153 my $installer = $class->build_sub_installer($pack, $name, '@');
154 $installer->(sub :lvalue {
155 #{ no warnings 'uninitialized'; warn 'INST: '.join(', ', @_)."\n"; }
157 if (ref $_[0] eq 'HASH') {
160 my @ret = $run->(undef, undef, @_);
163 my $r = $run->(undef, undef, @_);
171 $setup_for_args{$name} = [
174 my ($usepack, $use, $inpack, $name, $proto, $shift_hashref, $traits) = @_;
175 my $extra_code = $compile->($name, $proto, $traits);
176 my $main_handler = sub { shift if $shift_hashref;
177 ("DONE", $run->($name, $proto, @_));
180 if (defined $proto) {
181 $name_h = sub :lvalue { return my $sv; };
183 } elsif (defined $name && length $name) {
184 $name_h = $main_handler;
187 $extra_code = '}, sub {'.$extra_code;
188 return ($name_h, $XX, $extra_code);
192 $class->setup_for($pack, \%setup_for_args);
195 sub install_declarator {
196 my ($class, $target_pack, $target_name, $flags, $filter, $handler) = @_;
197 $class->setup_declarators($target_pack, {
206 sub linestr_callback_rv2cv {
207 my ($name, $offset) = @_;
208 $offset += toke_move_past_token($offset);
209 my $pack = get_curstash_name();
210 my $flags = $declarators{$pack}{$name};
211 my ($found_name, $found_proto);
212 if ($flags & DECLARE_NAME) {
213 $offset += toke_skipspace($offset);
214 my $linestr = get_linestr();
215 if (substr($linestr, $offset, 2) eq '::') {
216 substr($linestr, $offset, 2) = '';
217 set_linestr($linestr);
219 if (my $len = toke_scan_word($offset, $flags & DECLARE_PACKAGE)) {
220 $found_name = substr($linestr, $offset, $len);
224 if ($flags & DECLARE_PROTO) {
225 $offset += toke_skipspace($offset);
226 my $linestr = get_linestr();
227 if (substr($linestr, $offset, 1) eq '(') {
228 my $length = toke_scan_str($offset);
229 $found_proto = get_lex_stuff();
232 ($found_name ? ' ' : '=')
233 .'X'.(' ' x length($found_proto));
234 $linestr = get_linestr();
235 substr($linestr, $offset, $length) = $replace;
236 set_linestr($linestr);
240 my @args = ($pack, $name, $pack, $found_name, $found_proto);
241 $offset += toke_skipspace($offset);
242 my $linestr = get_linestr();
243 if (substr($linestr, $offset, 1) eq '{') {
244 my $ret = init_declare(@args);
246 if (defined $ret && length $ret) {
247 substr($linestr, $offset, 0) = $ret;
248 set_linestr($linestr);
253 #warn "linestr now ${linestr}";
256 sub linestr_callback_const {
257 my ($name, $offset) = @_;
258 my $pack = get_curstash_name();
259 my $flags = $declarators{$pack}{$name};
260 if ($flags & DECLARE_NAME) {
261 $offset += toke_move_past_token($offset);
262 $offset += toke_skipspace($offset);
263 if (toke_scan_word($offset, $flags & DECLARE_PACKAGE)) {
264 my $linestr = get_linestr();
265 substr($linestr, $offset, 0) = '::';
266 set_linestr($linestr);
271 sub linestr_callback {
274 my $pack = get_curstash_name();
275 my $handlers = $declarator_handlers{$pack}{$name};
276 if (ref $handlers eq 'CODE') {
277 my $meth = "linestr_callback_${type}";
278 __PACKAGE__->can($meth)->(@_);
279 } elsif (ref $handlers eq 'HASH') {
280 if ($handlers->{$type}) {
281 $handlers->{$type}->(@_);
284 die "PANIC: unknown thing in handlers for $pack $name: $handlers";
290 Devel::Declare - Adding keywords to perl, in perl
294 use Method::Signatures;
299 # Use some new and exciting syntax like:
300 method hello (Str :$who, Int :$age where { $_ > 0 }) {
301 $self->say("Hello ${who}, I am ${age} years old!");
306 L<Devel::Declare> can install subroutines called declarators which locally take
307 over Perl's parser, allowing the creation of new syntax.
309 This document describes how to create a simple declarator.
313 We'll demonstrate the usage of C<Devel::Declare> with a motivating example: a new
314 C<method> keyword, which acts like the builtin C<sub>, but automatically unpacks
315 C<$self> and the other arguments.
320 =head2 Creating a declarator with C<setup_for>
322 You will typically create
328 Devel::Declare->setup_for(
330 { method => { const => \&parser } }
333 *{$caller.'::method'} = sub (&) {};
336 Starting from the end of this import routine, you'll see that we're creating a
337 subroutine called C<method> in the caller's namespace. Yes, that's just a normal
338 subroutine, and it does nothing at all (yet!) Note the prototype C<(&)> which means
339 that the caller would call it like so:
342 my ($self, $arg1, $arg2) = @_;
346 However we want to be able to call it like this
348 method foo ($arg1, $arg2) {
352 That's why we call C<setup_for> above, to register the declarator 'method' with a custom
353 parser, as per the next section. It acts on an optype, usually C<'const'> as above.
354 (Other valid values are C<'check'> and C<'rv2cv'>).
356 For a simpler way to install new methods, see also L<Devel::Declare::MethodInstaller::Simple>
358 =head2 Writing a parser subroutine
360 This subroutine is called at I<compilation> time, and allows you to read the custom
361 syntaxes that we want (in a syntax that may or may not be valid core Perl 5) and
362 munge it so that the result will be parsed by the C<perl> compiler.
364 For this example, we're defining some globals for convenience:
366 our ($Declarator, $Offset);
368 Then we define a parser subroutine to handle our declarator. We'll look at this in
372 local ($Declarator, $Offset) = @_;
374 C<Devel::Declare> provides some very low level utility methods to parse character
375 strings. We'll define some useful higher level routines below for convenience,
376 and we can use these to parse the various elements in our new syntax.
378 Notice how our parser subroutine is invoked at compile time,
379 when the C<perl> parser is pointed just I<before> the declarator name.
381 skip_declarator; # step past 'method'
382 my $name = strip_name; # strip out the name 'foo', if present
383 my $proto = strip_proto; # strip out the prototype '($arg1, $arg2)', if present
385 Now we can prepare some code to 'inject' into the new subroutine. For example we
386 might want the method as above to have C<my ($self, $arg1, $arg2) = @_> injected at
387 the beginning of it. We also do some clever stuff with scopes that we'll look
390 my $inject = make_proto_unwrap($proto);
392 $inject = scope_injector_call().$inject;
394 inject_if_block($inject);
396 We've now managed to change C<method ($arg1, $arg2) { ... }> into C<method {
397 injected_code; ... }>. This will compile... but we've lost the name of the
400 In a cute (or horrifying, depending on your perspective) trick, we temporarily
401 change the definition of the subroutine C<method> itself, to specialise it with
402 the C<$name> we stripped, so that it assigns the code block to that name.
404 Even though the I<next> time C<method> is compiled, it will be
405 redefined again, C<perl> caches these definitions in its parse
406 tree, so we'll always get the right one!
408 Note that we also handle the case where there was no name, allowing
409 an anonymous method analogous to an anonymous subroutine.
412 $name = join('::', Devel::Declare::get_curstash_name(), $name)
413 unless ($name =~ /::/);
414 shadow(sub (&) { no strict 'refs'; *{$name} = shift; });
416 shadow(sub (&) { shift });
421 =head2 Parser utilities in detail
423 For simplicity, we're using global variables like C<$Offset> in these examples.
424 You may prefer to look at L<Devel::Declare::Context::Simple>, which
425 encapsulates the context much more cleanly.
427 =head3 C<skip_declarator>
429 This simple parser just moves across a 'token'. The common case is
430 to skip the declarator, i.e. to move to the end of the string
431 'method' and before the prototype and code block.
433 sub skip_declarator {
434 $Offset += Devel::Declare::toke_move_past_token($Offset);
437 =head4 C<toke_move_past_token>
439 This builtin parser simply moves past a 'token' (matching C</[a-zA-Z_]\w*/>)
440 It takes an offset into the source document, and skips past the token.
441 It returns the number of characters skipped.
445 This parser skips any whitespace, then scans the next word (again matching a
446 'token'). We can then analyse the current line, and manipulate it (using pure
447 Perl). In this case we take the name of the method out, and return it.
451 if (my $len = Devel::Declare::toke_scan_word($Offset, 1)) {
452 my $linestr = Devel::Declare::get_linestr();
453 my $name = substr($linestr, $Offset, $len);
454 substr($linestr, $Offset, $len) = '';
455 Devel::Declare::set_linestr($linestr);
461 =head4 C<toke_scan_word>
463 This builtin parser, given an offset into the source document,
464 matches a 'token' as above but does not skip. It returns the
465 length of the token matched, if any.
467 =head4 C<get_linestr>
469 This builtin returns the full text of the current line of the source document.
471 =head4 C<set_linestr>
473 This builtin sets the full text of the current line of the source document.
477 This parser skips whitsepace.
480 $Offset += Devel::Declare::toke_skipspace($Offset);
483 =head4 C<toke_skipspace>
485 This builtin parser, given an offset into the source document,
486 skips over any whitespace, and returns the number of characters
489 =head3 C<strip_proto>
491 This is a more complex parser that checks if it's found something that
492 starts with C<'('> and returns everything till the matching C<')'>.
497 my $linestr = Devel::Declare::get_linestr();
498 if (substr($linestr, $Offset, 1) eq '(') {
499 my $length = Devel::Declare::toke_scan_str($Offset);
500 my $proto = Devel::Declare::get_lex_stuff();
501 Devel::Declare::clear_lex_stuff();
502 $linestr = Devel::Declare::get_linestr();
503 substr($linestr, $Offset, $length) = '';
504 Devel::Declare::set_linestr($linestr);
510 =head4 C<toke_scan_str>
512 This builtin parser uses Perl's own parsing routines to match a "stringlike"
513 expression. Handily, this includes bracketed expressions (just think about
514 things like C<q(this is a quote)>).
516 Also it Does The Right Thing with nested delimiters (like C<q(this (is (a) quote))>).
518 It returns the effective length of the expression matched. Really, what
519 it returns is the difference in position between where the string started,
520 within the buffer, and where it finished. If the string extended across
521 multiple lines then the contents of the buffer may have been completely
522 replaced by the new lines, so this position difference is not the same
523 thing as the actual length of the expression matched. However, because
524 moving backward in the buffer causes problems, the function arranges
525 for the effective length to always be positive, padding the start of
526 the buffer if necessary.
528 Use C<get_lex_stuff> to get the actual matched text, the content of
529 the string. Because of the behaviour around multiline strings, you
530 can't reliably get this from the buffer. In fact, after the function
531 returns, you can't rely on any content of the buffer preceding the end
534 If the string being scanned is not well formed (has no closing delimiter),
535 C<toke_scan_str> returns C<undef>. In this case you cannot rely on the
536 contents of the buffer.
538 =head4 C<get_lex_stuff>
540 This builtin returns what was matched by C<toke_scan_str>. To avoid segfaults,
541 you should call C<clear_lex_stuff> immediately afterwards.
543 =head2 Munging the subroutine
545 Let's look at what we need to do in detail.
547 =head3 C<make_proto_unwrap>
549 We may have defined our method in different ways, which will result
550 in a different value for our prototype, as parsed above. For example:
552 method foo { # undefined
554 method foo ($arg1) { # '$arg1'
556 We deal with them as follows, and return the appropriate C<my ($self, ...) = @_;>
559 sub make_proto_unwrap {
561 my $inject = 'my ($self';
562 if (defined $proto) {
563 $inject .= ", $proto" if length($proto);
564 $inject .= ') = @_; ';
566 $inject .= ') = shift;';
571 =head3 C<inject_if_block>
573 Now we need to inject it after the opening C<'{'> of the method body.
574 We can do this with the building blocks we defined above like C<skipspace>
577 sub inject_if_block {
580 my $linestr = Devel::Declare::get_linestr;
581 if (substr($linestr, $Offset, 1) eq '{') {
582 substr($linestr, $Offset+1, 0) = $inject;
583 Devel::Declare::set_linestr($linestr);
587 =head3 C<scope_injector_call>
589 We want to be able to handle both named and anonymous methods. i.e.
591 method foo () { ... }
592 my $meth = method () { ... };
594 These will then get rewritten as
597 my $meth = method { ... };
599 where 'method' is a subroutine that takes a code block. Spot the problem?
600 The first one doesn't have a semicolon at the end of it! Unlike 'sub' which
601 is a builtin, this is just a normal statement, so we need to terminate it.
602 Luckily, using C<B::Hooks::EndOfScope>, we can do this!
604 use B::Hooks::EndOfScope;
606 We'll add this to what gets 'injected' at the beginning of the method source.
608 sub scope_injector_call {
609 return ' BEGIN { MethodHandlers::inject_scope }; ';
612 So at the beginning of every method, we are passing a callback that will get invoked
613 at the I<end> of the method's compilation... i.e. exactly then the closing C<'}'>
618 my $linestr = Devel::Declare::get_linestr;
619 my $offset = Devel::Declare::get_linestr_offset;
620 substr($linestr, $offset, 0) = ';';
621 Devel::Declare::set_linestr($linestr);
625 =head2 Shadowing each method.
629 We override the current definition of 'method' using C<shadow>.
632 my $pack = Devel::Declare::get_curstash_name;
633 Devel::Declare::shadow_sub("${pack}::${Declarator}", $_[0]);
636 For a named method we invoked like this:
638 shadow(sub (&) { no strict 'refs'; *{$name} = shift; });
640 So in the case of a C<method foo { ... }>, this call would redefine C<method>
641 to be a subroutine that exports 'sub foo' as the (munged) contents of C<{...}>.
643 The case of an anonymous method is also cute:
645 shadow(sub (&) { shift });
649 my $meth = method () { ... };
651 is rewritten with C<method> taking the codeblock, and returning it as is to become
652 the value of C<$meth>.
654 =head4 C<get_curstash_name>
656 This returns the package name I<currently being compiled>.
660 Handles the details of redefining the subroutine.
664 One of the best ways to learn C<Devel::Declare> is still to look at
667 L<http://cpants.perl.org/dist/used_by/Devel-Declare>.
671 Matt S Trout - E<lt>mst@shadowcat.co.ukE<gt> - original author
673 Company: http://www.shadowcat.co.uk/
674 Blog: http://chainsawblues.vox.com/
676 Florian Ragwitz E<lt>rafl@debian.orgE<gt> - maintainer
678 osfameron E<lt>osfameron@cpan.orgE<gt> - first draft of documentation
680 =head1 COPYRIGHT AND LICENSE
682 This library is free software under the same terms as perl itself
684 Copyright (c) 2007, 2008, 2009 Matt S Trout
686 Copyright (c) 2008, 2009 Florian Ragwitz
688 stolen_chunk_of_toke.c based on toke.c from the perl core, which is
690 Copyright (C) 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999,
691 2000, 2001, 2002, 2003, 2004, 2005, 2006, by Larry Wall and others