package Devel::Declare;
+# ABSTRACT: Adding keywords to perl, in perl
use strict;
use warnings;
use 5.008001;
-our $VERSION = '0.001005';
-
-# mirrored in Declare.xs as DD_HANDLE_*
+our $VERSION = '0.006015';
use constant DECLARE_NAME => 1;
use constant DECLARE_PROTO => 2;
use vars qw(%declarators %declarator_handlers @ISA);
use base qw(DynaLoader);
use Scalar::Util 'set_prototype';
+use B::Hooks::OP::Check 0.19;
bootstrap Devel::Declare;
@ISA = ();
+initialize();
+
sub import {
my ($class, %args) = @_;
my $target = caller;
} elsif (ref($info) eq 'CODE') {
$flags = DECLARE_NAME;
$sub = $info;
+ } elsif (ref($info) eq 'HASH') {
+ $flags = 1;
+ $sub = $info;
} else {
- die "Info for sub ${key} must be [ \$flags, \$sub ] or \$sub";
+ die "Info for sub ${key} must be [ \$flags, \$sub ] or \$sub or handler hashref";
}
$declarators{$target}{$key} = $flags;
$declarator_handlers{$target}{$key} = $sub;
my ($class, $target) = @_;
delete $declarators{$target};
delete $declarator_handlers{$target};
- teardown();
}
my $temp_name;
my $temp_save;
sub init_declare {
- my ($usepack, $use, $inpack, $name, $proto) = @_;
+ my ($usepack, $use, $inpack, $name, $proto, $traits) = @_;
my ($name_h, $XX_h, $extra_code)
= $declarator_handlers{$usepack}{$use}->(
- $usepack, $use, $inpack, $name, $proto, defined(wantarray)
+ $usepack, $use, $inpack, $name, $proto, defined(wantarray), $traits
);
($temp_name, $temp_save) = ([], []);
if ($name) {
$name = "${inpack}::${name}" unless $name =~ /::/;
- push(@$temp_name, $name);
- no strict 'refs';
- push(@$temp_save, \&{$name});
- no warnings 'redefine';
- no warnings 'prototype';
- *{$name} = $name_h;
+ shadow_sub($name, $name_h);
}
if ($XX_h) {
- push(@$temp_name, "${inpack}::X");
- no strict 'refs';
- push(@$temp_save, \&{"${inpack}::X"});
- no warnings 'redefine';
- no warnings 'prototype';
- *{"${inpack}::X"} = $XX_h;
+ shadow_sub("${inpack}::X", $XX_h);
}
if (defined wantarray) {
return $extra_code || '0;';
}
}
+sub shadow_sub {
+ my ($name, $cr) = @_;
+ push(@$temp_name, $name);
+ no strict 'refs';
+ my ($pack, $pname) = ($name =~ m/(.+)::([^:]+)/);
+ push(@$temp_save, $pack->can($pname));
+ no warnings 'redefine';
+ no warnings 'prototype';
+ *{$name} = $cr;
+ set_in_declare(~~@{$temp_name||[]});
+}
+
sub done_declare {
no strict 'refs';
my $name = shift(@{$temp_name||[]});
no warnings 'prototype';
*{"${temp_pack}::${name}"} = $saved;
}
+ set_in_declare(~~@{$temp_name||[]});
}
sub build_sub_installer {
$setup_for_args{$name} = [
$flags,
sub {
- my ($usepack, $use, $inpack, $name, $proto, $shift_hashref) = @_;
- my $extra_code = $compile->($name, $proto);
+ my ($usepack, $use, $inpack, $name, $proto, $shift_hashref, $traits) = @_;
+ my $extra_code = $compile->($name, $proto, $traits);
my $main_handler = sub { shift if $shift_hashref;
("DONE", $run->($name, $proto, @_));
};
});
}
+sub linestr_callback_rv2cv {
+ my ($name, $offset) = @_;
+ $offset += toke_move_past_token($offset);
+ my $pack = get_curstash_name();
+ my $flags = $declarators{$pack}{$name};
+ my ($found_name, $found_proto);
+ if ($flags & DECLARE_NAME) {
+ $offset += toke_skipspace($offset);
+ my $linestr = get_linestr();
+ if (substr($linestr, $offset, 2) eq '::') {
+ substr($linestr, $offset, 2) = '';
+ set_linestr($linestr);
+ }
+ if (my $len = toke_scan_word($offset, $flags & DECLARE_PACKAGE)) {
+ $found_name = substr($linestr, $offset, $len);
+ $offset += $len;
+ }
+ }
+ if ($flags & DECLARE_PROTO) {
+ $offset += toke_skipspace($offset);
+ my $linestr = get_linestr();
+ if (substr($linestr, $offset, 1) eq '(') {
+ my $length = toke_scan_str($offset);
+ $found_proto = get_lex_stuff();
+ clear_lex_stuff();
+ my $replace =
+ ($found_name ? ' ' : '=')
+ .'X'.(' ' x length($found_proto));
+ $linestr = get_linestr();
+ substr($linestr, $offset, $length) = $replace;
+ set_linestr($linestr);
+ $offset += $length;
+ }
+ }
+ my @args = ($pack, $name, $pack, $found_name, $found_proto);
+ $offset += toke_skipspace($offset);
+ my $linestr = get_linestr();
+ if (substr($linestr, $offset, 1) eq '{') {
+ my $ret = init_declare(@args);
+ $offset++;
+ if (defined $ret && length $ret) {
+ substr($linestr, $offset, 0) = $ret;
+ set_linestr($linestr);
+ }
+ } else {
+ init_declare(@args);
+ }
+ #warn "linestr now ${linestr}";
+}
+
+sub linestr_callback_const {
+ my ($name, $offset) = @_;
+ my $pack = get_curstash_name();
+ my $flags = $declarators{$pack}{$name};
+ if ($flags & DECLARE_NAME) {
+ $offset += toke_move_past_token($offset);
+ $offset += toke_skipspace($offset);
+ if (toke_scan_word($offset, $flags & DECLARE_PACKAGE)) {
+ my $linestr = get_linestr();
+ substr($linestr, $offset, 0) = '::';
+ set_linestr($linestr);
+ }
+ }
+}
+
+sub linestr_callback {
+ my $type = shift;
+ my $name = $_[0];
+ my $pack = get_curstash_name();
+ my $handlers = $declarator_handlers{$pack}{$name};
+ if (ref $handlers eq 'CODE') {
+ my $meth = "linestr_callback_${type}";
+ __PACKAGE__->can($meth)->(@_);
+ } elsif (ref $handlers eq 'HASH') {
+ if ($handlers->{$type}) {
+ $handlers->{$type}->(@_);
+ }
+ } else {
+ die "PANIC: unknown thing in handlers for $pack $name: $handlers";
+ }
+}
+
=head1 NAME
-Devel::Declare -
+Devel::Declare - Adding keywords to perl, in perl
=head1 SYNOPSIS
-Look at the tests. This module is currently on CPAN to ease smoke testing
-and allow early adopters who've been involved in the design to experiment
-with it.
+ use Method::Signatures;
+ # or ...
+ use MooseX::Declare;
+ # etc.
+
+ # Use some new and exciting syntax like:
+ method hello (Str :$who, Int :$age where { $_ > 0 }) {
+ $self->say("Hello ${who}, I am ${age} years old!");
+ }
=head1 DESCRIPTION
-=head2 import
+L<Devel::Declare> can install subroutines called declarators which locally take
+over Perl's parser, allowing the creation of new syntax.
+
+This document describes how to create a simple declarator.
+
+=head1 USAGE
+
+We'll demonstrate the usage of C<Devel::Declare> with a motivating example: a new
+C<method> keyword, which acts like the builtin C<sub>, but automatically unpacks
+C<$self> and the other arguments.
+
+ package My::Methods;
+ use Devel::Declare;
+
+=head2 Creating a declarator with C<setup_for>
+
+You will typically create
+
+ sub import {
+ my $class = shift;
+ my $caller = caller;
- use Devel::Declare qw(list of subs);
+ Devel::Declare->setup_for(
+ $caller,
+ { method => { const => \&parser } }
+ );
+ no strict 'refs';
+ *{$caller.'::method'} = sub (&) {};
+ }
+
+Starting from the end of this import routine, you'll see that we're creating a
+subroutine called C<method> in the caller's namespace. Yes, that's just a normal
+subroutine, and it does nothing at all (yet!) Note the prototype C<(&)> which means
+that the caller would call it like so:
+
+ method {
+ my ($self, $arg1, $arg2) = @_;
+ ...
+ }
+
+However we want to be able to call it like this
+
+ method foo ($arg1, $arg2) {
+ ...
+ }
+
+That's why we call C<setup_for> above, to register the declarator 'method' with a custom
+parser, as per the next section. It acts on an optype, usually C<'const'> as above.
+(Other valid values are C<'check'> and C<'rv2cv'>).
+
+For a simpler way to install new methods, see also L<Devel::Declare::MethodInstaller::Simple>
+
+=head2 Writing a parser subroutine
+
+This subroutine is called at I<compilation> time, and allows you to read the custom
+syntaxes that we want (in a syntax that may or may not be valid core Perl 5) and
+munge it so that the result will be parsed by the C<perl> compiler.
+
+For this example, we're defining some globals for convenience:
+
+ our ($Declarator, $Offset);
+
+Then we define a parser subroutine to handle our declarator. We'll look at this in
+a few chunks.
+
+ sub parser {
+ local ($Declarator, $Offset) = @_;
+
+C<Devel::Declare> provides some very low level utility methods to parse character
+strings. We'll define some useful higher level routines below for convenience,
+and we can use these to parse the various elements in our new syntax.
+
+Notice how our parser subroutine is invoked at compile time,
+when the C<perl> parser is pointed just I<before> the declarator name.
+
+ skip_declarator; # step past 'method'
+ my $name = strip_name; # strip out the name 'foo', if present
+ my $proto = strip_proto; # strip out the prototype '($arg1, $arg2)', if present
-Calls Devel::Declare->setup_for(__PACKAGE__ => \@list_of_subs);
+Now we can prepare some code to 'inject' into the new subroutine. For example we
+might want the method as above to have C<my ($self, $arg1, $arg2) = @_> injected at
+the beginning of it. We also do some clever stuff with scopes that we'll look
+at shortly.
-=head2 unimport
+ my $inject = make_proto_unwrap($proto);
+ if (defined $name) {
+ $inject = scope_injector_call().$inject;
+ }
+ inject_if_block($inject);
+
+We've now managed to change C<method ($arg1, $arg2) { ... }> into C<method {
+injected_code; ... }>. This will compile... but we've lost the name of the
+method!
+
+In a cute (or horrifying, depending on your perspective) trick, we temporarily
+change the definition of the subroutine C<method> itself, to specialise it with
+the C<$name> we stripped, so that it assigns the code block to that name.
+
+Even though the I<next> time C<method> is compiled, it will be
+redefined again, C<perl> caches these definitions in its parse
+tree, so we'll always get the right one!
+
+Note that we also handle the case where there was no name, allowing
+an anonymous method analogous to an anonymous subroutine.
+
+ if (defined $name) {
+ $name = join('::', Devel::Declare::get_curstash_name(), $name)
+ unless ($name =~ /::/);
+ shadow(sub (&) { no strict 'refs'; *{$name} = shift; });
+ } else {
+ shadow(sub (&) { shift });
+ }
+ }
+
+
+=head2 Parser utilities in detail
- no Devel::Declare;
+For simplicity, we're using global variables like C<$Offset> in these examples.
+You may prefer to look at L<Devel::Declare::Context::Simple>, which
+encapsulates the context much more cleanly.
-Calls Devel::Declare->teardown_for(__PACKAGE__);
+=head3 C<skip_declarator>
-=head2 setup_for
+This simple parser just moves across a 'token'. The common case is
+to skip the declarator, i.e. to move to the end of the string
+'method' and before the prototype and code block.
+
+ sub skip_declarator {
+ $Offset += Devel::Declare::toke_move_past_token($Offset);
+ }
+
+=head4 C<toke_move_past_token>
+
+This builtin parser simply moves past a 'token' (matching C</[a-zA-Z_]\w*/>)
+It takes an offset into the source document, and skips past the token.
+It returns the number of characters skipped.
+
+=head3 C<strip_name>
+
+This parser skips any whitespace, then scans the next word (again matching a
+'token'). We can then analyse the current line, and manipulate it (using pure
+Perl). In this case we take the name of the method out, and return it.
+
+ sub strip_name {
+ skipspace;
+ if (my $len = Devel::Declare::toke_scan_word($Offset, 1)) {
+ my $linestr = Devel::Declare::get_linestr();
+ my $name = substr($linestr, $Offset, $len);
+ substr($linestr, $Offset, $len) = '';
+ Devel::Declare::set_linestr($linestr);
+ return $name;
+ }
+ return;
+ }
- Devel::Declare->setup_for($package => \@subnames);
+=head4 C<toke_scan_word>
-Installs declarator magic (unless already installed) and registers
-"${package}::$name" for each member of @subnames
+This builtin parser, given an offset into the source document,
+matches a 'token' as above but does not skip. It returns the
+length of the token matched, if any.
-=head2 teardown_for
+=head4 C<get_linestr>
- Devel::Declare->teardown_for($package);
+This builtin returns the full text of the current line of the source document.
-Deregisters all subs currently registered for $package and uninstalls
-declarator magic if number of teardown_for calls matches number of setup_for
-calls.
+=head4 C<set_linestr>
-=head1 AUTHOR
+This builtin sets the full text of the current line of the source document.
+Beware that injecting a newline into the middle of the line is likely
+to fail in surprising ways. Generally, Perl's parser can rely on the
+`current line' actually being only a single line. Use other kinds of
+whitespace instead, in the code that you inject.
-Matt S Trout - <mst@shadowcat.co.uk>
+=head3 C<skipspace>
+
+This parser skips whitsepace.
+
+ sub skipspace {
+ $Offset += Devel::Declare::toke_skipspace($Offset);
+ }
+
+=head4 C<toke_skipspace>
+
+This builtin parser, given an offset into the source document,
+skips over any whitespace, and returns the number of characters
+skipped.
+
+=head3 C<strip_proto>
+
+This is a more complex parser that checks if it's found something that
+starts with C<'('> and returns everything till the matching C<')'>.
+
+ sub strip_proto {
+ skipspace;
+
+ my $linestr = Devel::Declare::get_linestr();
+ if (substr($linestr, $Offset, 1) eq '(') {
+ my $length = Devel::Declare::toke_scan_str($Offset);
+ my $proto = Devel::Declare::get_lex_stuff();
+ Devel::Declare::clear_lex_stuff();
+ $linestr = Devel::Declare::get_linestr();
+ substr($linestr, $Offset, $length) = '';
+ Devel::Declare::set_linestr($linestr);
+ return $proto;
+ }
+ return;
+ }
+
+=head4 C<toke_scan_str>
+
+This builtin parser uses Perl's own parsing routines to match a "stringlike"
+expression. Handily, this includes bracketed expressions (just think about
+things like C<q(this is a quote)>).
+
+Also it Does The Right Thing with nested delimiters (like C<q(this (is (a) quote))>).
+
+It returns the effective length of the expression matched. Really, what
+it returns is the difference in position between where the string started,
+within the buffer, and where it finished. If the string extended across
+multiple lines then the contents of the buffer may have been completely
+replaced by the new lines, so this position difference is not the same
+thing as the actual length of the expression matched. However, because
+moving backward in the buffer causes problems, the function arranges
+for the effective length to always be positive, padding the start of
+the buffer if necessary.
+
+Use C<get_lex_stuff> to get the actual matched text, the content of
+the string. Because of the behaviour around multiline strings, you
+can't reliably get this from the buffer. In fact, after the function
+returns, you can't rely on any content of the buffer preceding the end
+of the string.
+
+If the string being scanned is not well formed (has no closing delimiter),
+C<toke_scan_str> returns C<undef>. In this case you cannot rely on the
+contents of the buffer.
+
+=head4 C<get_lex_stuff>
+
+This builtin returns what was matched by C<toke_scan_str>. To avoid segfaults,
+you should call C<clear_lex_stuff> immediately afterwards.
+
+=head2 Munging the subroutine
+
+Let's look at what we need to do in detail.
+
+=head3 C<make_proto_unwrap>
+
+We may have defined our method in different ways, which will result
+in a different value for our prototype, as parsed above. For example:
+
+ method foo { # undefined
+ method foo () { # ''
+ method foo ($arg1) { # '$arg1'
+
+We deal with them as follows, and return the appropriate C<my ($self, ...) = @_;>
+string.
+
+ sub make_proto_unwrap {
+ my ($proto) = @_;
+ my $inject = 'my ($self';
+ if (defined $proto) {
+ $inject .= ", $proto" if length($proto);
+ $inject .= ') = @_; ';
+ } else {
+ $inject .= ') = shift;';
+ }
+ return $inject;
+ }
+
+=head3 C<inject_if_block>
+
+Now we need to inject it after the opening C<'{'> of the method body.
+We can do this with the building blocks we defined above like C<skipspace>
+and C<get_linestr>.
+
+ sub inject_if_block {
+ my $inject = shift;
+ skipspace;
+ my $linestr = Devel::Declare::get_linestr;
+ if (substr($linestr, $Offset, 1) eq '{') {
+ substr($linestr, $Offset+1, 0) = $inject;
+ Devel::Declare::set_linestr($linestr);
+ }
+ }
+
+=head3 C<scope_injector_call>
+
+We want to be able to handle both named and anonymous methods. i.e.
+
+ method foo () { ... }
+ my $meth = method () { ... };
+
+These will then get rewritten as
+
+ method { ... }
+ my $meth = method { ... };
+
+where 'method' is a subroutine that takes a code block. Spot the problem?
+The first one doesn't have a semicolon at the end of it! Unlike 'sub' which
+is a builtin, this is just a normal statement, so we need to terminate it.
+Luckily, using C<B::Hooks::EndOfScope>, we can do this!
+
+ use B::Hooks::EndOfScope;
+
+We'll add this to what gets 'injected' at the beginning of the method source.
+
+ sub scope_injector_call {
+ return ' BEGIN { MethodHandlers::inject_scope }; ';
+ }
+
+So at the beginning of every method, we are passing a callback that will get invoked
+at the I<end> of the method's compilation... i.e. exactly then the closing C<'}'>
+is compiled.
+
+ sub inject_scope {
+ on_scope_end {
+ my $linestr = Devel::Declare::get_linestr;
+ my $offset = Devel::Declare::get_linestr_offset;
+ substr($linestr, $offset, 0) = ';';
+ Devel::Declare::set_linestr($linestr);
+ };
+ }
+
+=head2 Shadowing each method.
+
+=head3 C<shadow>
+
+We override the current definition of 'method' using C<shadow>.
+
+ sub shadow {
+ my $pack = Devel::Declare::get_curstash_name;
+ Devel::Declare::shadow_sub("${pack}::${Declarator}", $_[0]);
+ }
+
+For a named method we invoked like this:
+
+ shadow(sub (&) { no strict 'refs'; *{$name} = shift; });
+
+So in the case of a C<method foo { ... }>, this call would redefine C<method>
+to be a subroutine that exports 'sub foo' as the (munged) contents of C<{...}>.
+
+The case of an anonymous method is also cute:
+
+ shadow(sub (&) { shift });
+
+This means that
+
+ my $meth = method () { ... };
+
+is rewritten with C<method> taking the codeblock, and returning it as is to become
+the value of C<$meth>.
+
+=head4 C<get_curstash_name>
+
+This returns the package name I<currently being compiled>.
+
+=head4 C<shadow_sub>
+
+Handles the details of redefining the subroutine.
+
+=head1 SEE ALSO
+
+One of the best ways to learn C<Devel::Declare> is still to look at
+modules that use it:
+
+L<http://cpants.perl.org/dist/used_by/Devel-Declare>.
+
+=head1 AUTHORS
+
+Matt S Trout - E<lt>mst@shadowcat.co.ukE<gt> - original author
Company: http://www.shadowcat.co.uk/
Blog: http://chainsawblues.vox.com/
-=head1 LICENSE
+Florian Ragwitz E<lt>rafl@debian.orgE<gt> - maintainer
+
+osfameron E<lt>osfameron@cpan.orgE<gt> - first draft of documentation
+
+=head1 COPYRIGHT AND LICENSE
This library is free software under the same terms as perl itself
+Copyright (c) 2007, 2008, 2009 Matt S Trout
+
+Copyright (c) 2008, 2009 Florian Ragwitz
+
+stolen_chunk_of_toke.c based on toke.c from the perl core, which is
+
+Copyright (C) 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999,
+2000, 2001, 2002, 2003, 2004, 2005, 2006, by Larry Wall and others
+
=cut
1;
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