Type::Tiny - tiny, yet Moo(se)-compatible type constraint
use Scalar::Util qw(looks_like_number);
use Type::Tiny;
my $NUM = "Type::Tiny"->new(
name => "Number",
constraint => sub { looks_like_number($_) },
message => sub { "$_ ain't a number" },
);
package Ermintrude {
use Moo;
has favourite_number => (is => "ro", isa => $NUM);
}
package Bullwinkle {
use Moose;
has favourite_number => (is => "ro", isa => $NUM);
}
package Maisy {
use Mouse;
has favourite_number => (is => "ro", isa => $NUM);
}
This module is covered by the
Type-Tiny stability policy.
the Type::Tiny manpage is a tiny class for creating Moose-like type constraint
objects which are compatible with Moo, Moose and Mouse.
Maybe now we won't need to have separate MooseX, MouseX and MooX versions
of everything? We can but hope...
This documents the internals of the Type::Tiny manpage. the Type::Tiny::Manual manpage is
a better starting place if you're new.
- new(%attributes)
-
Moose-style constructor function.
Attributes are named values that may be passed to the constructor. For
each attribute, there is a corresponding reader method. For example:
my $type = Type::Tiny->new( name => "Foo" );
print $type->name, "\n"; # says "Foo"
These are the attributes you are likely to be most interested in
providing when creating your own type constraints, and most interested
in reading when dealing with type constraint objects.
- constraint
-
Coderef to validate a value (
$_) against the type constraint.
The coderef will not be called unless the value is known to pass any
parent type constraint (see parent below).
Alternatively, a string of Perl code checking $_ can be passed
as a parameter to the constructor, and will be converted to a coderef.
Defaults to sub { 1 } - i.e. a coderef that passes all values.
- parent
-
Optional attribute; parent type constraint. For example, an ``Integer''
type constraint might have a parent ``Number''.
If provided, must be a Type::Tiny object.
- inlined
-
A coderef which returns a string of Perl code suitable for inlining this
type. Optional.
If constraint (above) is a coderef generated via the Sub::Quote manpage, then
Type::Tiny may be able to automatically generate inlined for you.
If constraint (above) is a string, it will be able to.
- name
-
The name of the type constraint. These need to conform to certain naming
rules (they must begin with an uppercase letter and continue using only
letters, digits 0-9 and underscores).
Optional; if not supplied will be an anonymous type constraint.
- display_name
-
A name to display for the type constraint when stringified. These don't
have to conform to any naming rules. Optional; a default name will be
calculated from the
name.
- library
-
The package name of the type library this type is associated with.
Optional. Informational only: setting this attribute does not install
the type into the package.
- deprecated
-
Optional boolean indicating whether a type constraint is deprecated.
the Type::Library manpage will issue a warning if you attempt to import a deprecated
type constraint, but otherwise the type will continue to function as normal.
There will not be deprecation warnings every time you validate a value, for
instance. If omitted, defaults to the parent's deprecation status (or false
if there's no parent).
- message
-
Coderef that returns an error message when
$_ does not validate
against the type constraint. Optional (there's a vaguely sensible default.)
- coercion
-
A the Type::Coercion manpage object associated with this type.
Generally speaking this attribute should not be passed to the constructor;
you should rely on the default lazily-built coercion object.
You may pass coercion => 1 to the constructor to inherit coercions
from the constraint's parent. (This requires the parent constraint to have
a coercion.)
- my_methods
-
Experimenal hashref of additional methods that can be called on the type
constraint object.
The following additional attributes are used for parameterizable (e.g.
ArrayRef) and parameterized (e.g. ArrayRef[Int]) type
constraints. Unlike Moose, these aren't handled by separate subclasses.
- constraint_generator
-
Coderef that is called when a type constraint is parameterized. When called,
it is passed the list of parameters, though any parameter which looks like a
foreign type constraint (Moose type constraints, Mouse type constraints, etc,
and coderefs(!!!) >) is first coerced to a native Type::Tiny object.
Note that for compatibility with the Moose API, the base type is not
passed to the constraint generator, but can be found in the package variable
$Type::Tiny::parameterize_type. The first parameter is also available
as $_.
Types can be parameterized with an empty parameter list. For example,
in the Types::Standard manpage, Tuple is just an alias for ArrayRef but
Tuple[] will only allow zero-length arrayrefs to pass the constraint.
If you wish YourType and YourType[] to mean the same thing,
then do:
return $Type::Tiny::parameterize_type unless @_;
The constraint generator should generate and return a new constraint coderef
based on the parameters. Alternatively, the constraint generator can return a
fully-formed Type::Tiny object, in which case the name_generator,
inline_generator, and coercion_generator attributes documented below
are ignored.
Optional; providing a generator makes this type into a parameterizable
type constraint. If there is no generator, attempting to parameterize the
type constraint will throw an exception.
- name_generator
-
A coderef which generates a new display_name based on parameters. Called with
the same parameters and package variables as the
constraint_generator.
Expected to return a string.
Optional; the default is reasonable.
- inline_generator
-
A coderef which generates a new inlining coderef based on parameters. Called
with the same parameters and package variables as the
constraint_generator.
Expected to return a coderef.
Optional.
- coercion_generator
-
A coderef which generates a new the Type::Coercion manpage object based on parameters.
Called with the same parameters and package variables as the
constraint_generator. Expected to return a blessed object.
Optional.
- deep_explanation
-
This API is not finalized. Coderef used by the Error::TypeTiny::Assertion manpage to
peek inside parameterized types and figure out why a value doesn't pass the
constraint.
- parameters
-
In parameterized types, returns an arrayref of the parameters.
The following attributes should not be usually passed to the constructor;
unless you're doing something especially unusual, you should rely on the
default lazily-built return values.
- compiled_check
-
Coderef to validate a value (
$_[0]) against the type constraint.
This coderef is expected to also handle all validation for the parent
type constraints.
- complementary_type
-
A complementary type for this type. For example, the complementary type
for an integer type would be all things that are not integers, including
floating point numbers, but also alphabetic strings, arrayrefs, filehandles,
etc.
- moose_type, mouse_type
-
Objects equivalent to this type constraint, but as a
the Moose::Meta::TypeConstraint manpage or the Mouse::Meta::TypeConstraint manpage.
It should rarely be necessary to obtain a the Moose::Meta::TypeConstraint manpage
object from the Type::Tiny manpage because the the Type::Tiny manpage object itself should
be usable pretty much anywhere a the Moose::Meta::TypeConstraint manpage is expected.
These methods return booleans indicating information about the type
constraint. They are each tightly associated with a particular attribute.
(See Attributes.)
- has_parent, has_library, has_inlined, has_constraint_generator, has_inline_generator, has_coercion_generator, has_parameters, has_message, has_deep_explanation
-
Simple Moose-style predicate methods indicating the presence or
absence of an attribute.
- has_coercion
-
Predicate method with a little extra DWIM. Returns false if the coercion is
a no-op.
- is_anon
-
Returns true iff the type constraint does not have a
name.
- is_parameterized, is_parameterizable
-
Indicates whether a type has been parameterized (e.g.
ArrayRef[Int])
or could potentially be (e.g. ArrayRef).
The following methods are used for coercing and validating values
against a type constraint:
- check($value)
-
Returns true iff the value passes the type constraint.
- validate($value)
-
Returns the error message for the value; returns an explicit undef if the
value passes the type constraint.
- assert_valid($value)
-
Like
check($value) but dies if the value does not pass the type
constraint.
Yes, that's three very similar methods. Blame the Moose::Meta::TypeConstraint manpage
whose API I'm attempting to emulate. :-)
- assert_return($value)
-
Like
assert_valid($value) but returns the value if it passes the type
constraint.
This seems a more useful behaviour than assert_valid($value). I would
have just changed assert_valid($value) to do this, except that there
are edge cases where it could break Moose compatibility.
- get_message($value)
-
Returns the error message for the value; even if the value passes the type
constraint.
- validate_explain($value, $varname)
-
Like
validate but instead of a string error message, returns an arrayref
of strings explaining the reasoning why the value does not meet the type
constraint, examining parent types, etc.
The $varname is an optional string like '$foo' indicating the
name of the variable being checked.
- coerce($value)
-
Attempt to coerce
$value to this type.
- assert_coerce($value)
-
Attempt to coerce
$value to this type. Throws an exception if this is
not possible.
These methods generate new type constraint objects that inherit from the
constraint they are called upon:
- create_child_type(%attributes)
-
Construct a new Type::Tiny object with this object as its parent.
- where($coderef)
-
Shortcut for creating an anonymous child type constraint. Use it like
HashRef->where(sub { exists($_->{name}) }). That said, you can
get a similar result using overloaded &:
HashRef & sub { exists($_->{name}) }
Like the constraint attribute, this will accept a string of Perl
code:
HashRef->where('exists($_->{name})')
- child_type_class
-
The class that create_child_type will construct by default.
- parameterize(@parameters)
-
Creates a new parameterized type; throws an exception if called on a
non-parameterizable type.
- of(@parameters)
-
A cute alias for
parameterize. Use it like ArrayRef->of(Int).
- plus_coercions($type1, $code1, ...)
-
Shorthand for creating a new child type constraint with the same coercions
as this one, but then adding some extra coercions (at a higher priority than
the existing ones).
- plus_fallback_coercions($type1, $code1, ...)
-
Like
plus_coercions, but added at a lower priority.
- minus_coercions($type1, ...)
-
Shorthand for creating a new child type constraint with fewer type coercions.
- no_coercions
-
Shorthand for creating a new child type constraint with no coercions at all.
These methods allow you to determine a type constraint's relationship to
other type constraints in an organised hierarchy:
- equals($other), is_subtype_of($other), is_supertype_of($other), is_a_type_of($other)
-
Compare two types. See the Moose::Meta::TypeConstraint manpage for what these all mean.
(OK, Moose doesn't define
is_supertype_of, but you get the idea, right?)
Note that these have a slightly DWIM side to them. If you create two
the Type::Tiny::Class manpage objects which test the same class, they're considered
equal. And:
my $subtype_of_Num = Types::Standard::Num->create_child_type;
my $subtype_of_Int = Types::Standard::Int->create_child_type;
$subtype_of_Int->is_subtype_of( $subtype_of_Num ); # true
- strictly_equals($other), is_strictly_subtype_of($other), is_strictly_supertype_of($other), is_strictly_a_type_of($other)
-
Stricter versions of the type comparison functions. These only care about
explicit inheritance via
parent.
my $subtype_of_Num = Types::Standard::Num->create_child_type;
my $subtype_of_Int = Types::Standard::Int->create_child_type;
$subtype_of_Int->is_strictly_subtype_of( $subtype_of_Num ); # false
- parents
-
Returns a list of all this type constraint's ancestor constraints. For
example, if called on the
Str type constraint would return the list
(Value, Defined, Item, Any).
Due to a historical misunderstanding, this differs from the Moose
implementation of the parents method. In Moose, parents only returns the
immediate parent type constraints, and because type constraints only have
one immediate parent, this is effectively an alias for parent. The
extension module the MooseX::Meta::TypeConstraint::Intersection manpage is the only
place where multiple type constraints are returned; and they are returned
as an arrayref in violation of the base class' documentation. I'm keeping
my behaviour as it seems more useful. >
- find_parent($coderef)
-
Loops through the parent type constraints including the invocant
itself > and returns the nearest ancestor type constraint where the
coderef evaluates to true. Within the coderef the ancestor currently
being checked is
$_. Returns undef if there is no match.
In list context also returns the number of type constraints which had
been looped through before the matching constraint was found.
- coercibles
-
Return a type constraint which is the union of type constraints that can be
coerced to this one (including this one). If this type constraint has no
coercions, returns itself.
- type_parameter
-
In parameterized type constraints, returns the first item on the list of
parameters; otherwise returns undef. For example:
( ArrayRef[Int] )->type_parameter; # returns Int
( ArrayRef[Int] )->parent; # returns ArrayRef
Note that parameterizable type constraints can perfectly legitimately take
multiple parameters (several off the parameterizable type constraints in
the Types::Standard manpage do). This method only returns the first such parameter.
Attributes related to parameterizable and parameterized types
documents the parameters attribute, which returns an arrayref of all
the parameters.
The following methods are used to generate strings of Perl code which
may be pasted into stringy evaluated subs to perform type checks:
- can_be_inlined
-
Returns boolean indicating if this type can be inlined.
- inline_check($varname)
-
Creates a type constraint check for a particular variable as a string of
Perl code. For example:
print( Types::Standard::Num->inline_check('$foo') );
prints the following output:
(!ref($foo) && Scalar::Util::looks_like_number($foo))
For Moose-compat, there is an alias _inline_check for this method.
- inline_assert($varname)
-
Much like
inline_check but outputs a statement of the form:
die ... unless ...;
Note that if this type has a custom error message, the inlined code will
ignore this custom message!!
- qualified_name
-
For non-anonymous type constraints that have a library, returns a qualified
"MyLib::MyType" sort of name. Otherwise, returns the same as name.
- isa($class), can($method), AUTOLOAD(@args)
-
If Moose is loaded, then the combination of these methods is used to mock
a Moose::Meta::TypeConstraint.
If Mouse is loaded, then isa mocks Mouse::Meta::TypeConstraint.
- DOES($role)
-
Overridden to advertise support for various roles.
See also the Type::API::Constraint manpage, etc.
- TIESCALAR, TIEARRAY, TIEHASH
-
These are provided as hooks that wrap the Type::Tie manpage. (Type::Tie is distributed
separately, and can be used with non-Type::Tiny type constraints too.) They
allow the following to work:
use Types::Standard qw(Int);
tie my @list, Int;
push @list, 123, 456; # ok
push @list, "Hello"; # dies
The following methods exist for Moose/Mouse compatibility, but do not do
anything useful.
- compile_type_constraint
-
- hand_optimized_type_constraint
-
- has_hand_optimized_type_constraint
-
- inline_environment
-
- meta
-
-
Stringification is overloaded to return the qualified name.
-
Boolification is overloaded to always return true.
-
Coderefification is overloaded to call
assert_return.
-
On Perl 5.10.1 and above, smart match is overloaded to call
check.
-
The
== operator is overloaded to call equals.
-
The
< and > operators are overloaded to call is_subtype_of
and is_supertype_of.
-
The
~ operator is overloaded to call complementary_type.
-
The
| operator is overloaded to build a union of two type constraints.
See the Type::Tiny::Union manpage.
-
The
& operator is overloaded to build the intersection of two type
constraints. See the Type::Tiny::Intersection manpage.
Previous versions of Type::Tiny would overload the + operator to
call plus_coercions or plus_fallback_coercions as appropriate.
Support for this was dropped after 0.040.
- Type::Tiny::SUPPORT_SMARTMATCH
-
Indicates whether the smart match overload is supported on your
version of Perl.
- $Type::Tiny::DD
-
This undef by default but may be set to a coderef that Type::Tiny
and related modules will use to dump data structures in things like
error messages.
Otherwise Type::Tiny uses it's own routine to dump data structures.
$DD may then be set to a number to limit the lengths of the
dumps. (Default limit is 72.)
This is a package variable (rather than get/set class methods) to allow
for easy localization.
- PERL_TYPE_TINY_XS
-
Currently this has more effect on the Types::Standard manpage than Type::Tiny. In
future it may be used to trigger or suppress the loading XS implementations
of parts of Type::Tiny.
Please report any bugs to
http://rt.cpan.org/Dist/Display.html.
IRC: > support is available through in the #moops > channel
on irc.perl.org.
the Type::Tiny::Manual manpage, the Type::API manpage.
the Type::Library manpage, the Type::Utils manpage, the Types::Standard manpage, the Type::Coercion manpage.
the Type::Tiny::Class manpage, the Type::Tiny::Role manpage, the Type::Tiny::Duck manpage,
the Type::Tiny::Enum manpage, the Type::Tiny::Union manpage, the Type::Tiny::Intersection manpage.
the Moose::Meta::TypeConstraint manpage,
the Mouse::Meta::TypeConstraint manpage.
the Type::Params manpage.
Toby Inkster <tobyink@cpan.org>.
Thanks to Matt S Trout for advice on Moo integration.
This software is copyright (c) 2013-2014, 2017-2019 by Toby Inkster.
This is free software; you can redistribute it and/or modify it under
the same terms as the Perl 5 programming language system itself.
THIS PACKAGE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
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