| Parse::Method::Signatures - Perl6 like method signature parser |
Parse::Method::Signatures - Perl6 like method signature parser
Inspired by the Perl6::Signature manpage but streamlined to just support the subset deemed useful for TryCatch and the MooseX::Method::Signatures manpage.
There are only two public methods to this module, both of which should be called as class methods. Both methods accept either a single (non-ref) scalar as the value for the input attribute, or normal new style arguments (hash or hash-ref).
my $sig = Parse::Method::Signatures->signature( '(Str $foo)' )
Attempts to parse the (bracketed) method signature. Returns a value or croaks on error.
my $param = Parse::Method::Signatures->param( 'Str $foo where { length($_) < 10 }')
Attempts to parse the specification for a single parameter. Returns value or croaks on error.
All the attributes on this class are read-only.
Type: Str
The string to parse.
Type: Int
Offset into input at which to start parsing. Useful for using with Devel::Declare linestring
Default: Parse::Method::Signatures::Sig
Type: Str (loaded on demand class name)
Default: Parse::Method::Signatures::Param
Type: Str (loaded on demand class name)
Default: the Parse::Method::Signatures::TypeConstraint manpage
Type: Str (loaded on demand class name)
Class that is used to turn the parsed type constraint into an actual the Moose::Meta::TypeConstraint manpage object.
Type: ClassName
Let this module know which package it is parsing signatures form. This is entirely optional, and the only effect is has is on parsing type constraints.
If this attribute is set it is passed to type_constraint_class which can use it to introspect the package (commonly for the MooseX::Types manpage exported types). See find_registered_constraint in the Parse::Method::Signature::TypeConstraints manpage for more details.
Type: CodeRef
Passed to the constructor of type_constraint_class. Default implementation of this callback asks Moose for a type constrain matching the name passed in. If you have more complex requirements, such as parsing types created by the MooseX::Types manpage then you will want a callback similar to this:
# my $target_package defined elsewhere.
my $tc_cb = sub {
my ($pms_tc, $name) = @_;
my $code = $target_package->can($name);
$code ? eval { $code->() }
: $pms_tc->find_registered_constraint($name);
}
Note that the above example is better provided by providing the from_namespace attribute.
Like Perl6::Signature, the parsing of certain constructs is currently only a 'best effort' - specifically default values and where code blocks might not successfully for certain complex cases. Patches/Failing tests welcome.
Additionally, default value specifications are not evaluated which means that no such lexical or similar errors will not be produced by this module. Constant folding will also not be performed.
There are certain constructs that are simply too much hassle to avoid when the work around is simple. Currently the only cases that are known to parse wrong are when using anonymous variables (i.e. just sigils) in unpacked arrays. Take the following example:
method foo (ArrayRef [$, $], $some_value_we_care_about) {
In this case the $] is treated as one of perl's magic variables
(specifically, the patch level of the Perl interpreter) rather than a $
followed by a ] as was almost certainly intended. The work around for this
is simple: introduce a space between the characters:
method foo (ArrayRef [ $, $ ], $some_value_we_care_about) {
The same applies
Ash Berlin <ash@cpan.org>.
Thanks to Florian Ragwitz <rafl@debian.org>.
Many thanks to Piers Cawley to showing me the way to refactor my spaghetti code into something more manageable.
the Devel::Declare manpage which is used by most modules that use this (currently by all modules known to the author.)
http://github.com/ashb/trycatch/tree.
Licensed under the same terms as Perl itself.
This distribution copyright 2008-2009, Ash Berlin <ash@cpan.org>
| Parse::Method::Signatures - Perl6 like method signature parser |