NAME
Parse::Method::Signatures - Perl6 like method signature parser
DESCRIPTION
Inspired by Perl6::Signature but streamlined to just support the subset deemed useful for TryCatch and MooseX::Method::Signatures.
TODO
Document the parameter return types.
Probably lots of other things
METHODS
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).
signature
my $sig = Parse::Method::Signatures->signature( '(Str $foo)' )Attempts to parse the (bracketed) method signature. Returns a value or croaks on error.
param
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.
ATTRIBUTES
All the attributes on this class are read-only.
input
Type: Str
The string to parse.
offset
Type: Int
Offset into "input" at which to start parsing. Useful for using with Devel::Declare linestring
signature_class
Default: Parse::Method::Signatures::Sig
Type: Str (loaded on demand class name)
param_class
Default: Parse::Method::Signatures::Param
Type: Str (loaded on demand class name)
type_constraint_class
Default: Parse::Method::Signatures::TypeConstraint
Type: Str (loaded on demand class name)
Class that is used to turn the parsed type constraint into an actual Moose::Meta::TypeConstraint object.
from_namespace
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 (and type_constraint_callback is not) it is passed to "type_constraint_class" which can use it to introspect the package (commmonly for MooseX::Types exported types). See "find_registered_constraint" in Parse::Method::Signature::TypeConstraints for more details.
type_constraint_callback
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 MooseX::Types 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 "in_package" attribute.
CAVEATS
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 charcters:
method foo (ArrayRef [ $, $ ], $some_value_we_care_about) {The same applies
AUTHOR
Ash Berlin <ash@cpan.org>.
Thanks to Florian Ragwitz <rafl@debian.org>.
Many thanks to Piers Crawley to showing me the way to refactor my spaghetti code into something more manageable.
SEE ALSO
Devel::Declare which is used by most modules that use this (currently by all modules known to the author.)
http://github.com/ashb/trycatch/tree.
MooseX::Method::Signatures and MooseX::Declare which are due to be ported to use this module.
LICENSE
Licensed under the same terms as Perl itself.