show the first line here when testing with a harness

[gitmo/Moose.git] / TODO

## Uncontroversial Items

These items are reasonably well thought out, and can go in any major release.

### RT Tickets

RT#59478/RT#63000 - 0+ overload causes NV conversion on == on perls before
5.14 - this causes comparisons to fail when the number can't fit in an NV
without precision loss. I'd like to fix this in a more general way (forcing
anyone else who might be using == on tc objects to do weird things isn't very
good), although it's hard to test to see what actually works.

### Revise MetaRole API to reunify class/role metaroles:

    apply_metaroles(
        for   => $meta,
        roles => {
            attribute => [...],
            class     => [...],
            role_attribute => [ ... ],
        }
    );

If the $meta is a class, we apply the roles to the class. If it's a role, we
hold onto them and apply them as part of applying the role to a class.

To make this all work nicely, we'll probably want to track the original role
where a method was defined, just like we do with attributes currently. We'll
also need to store method modifiers with their original role, which may mean
adding some sort of Moose::Meta::Role::MethodModifier class.

For each role-specific thing (methods, attributes, etc.) we should allow a
`role_attribute`, `role_method`, etc. key. The common case will be that the
metaroles are intended for the consuming class, but we should allow for
metaroles on the role's metaobjects as well.

### Deprecate old-style Moose extensions

Moose extensions that work by calling `Moose->init_meta(metaclass =>
'Some::Custom::Metaclass', ...)` during their own init_meta should be
deprecated, so they can be removed later (this should fix the issues with
`init_meta` generation in Moose::Exporter, see RT51561)

This needs to wait until the previous fix gets in, since it will hopefully
eliminate the need to write custom init_meta methods entirely.

### Attributes in roles need to be able to participate in role composition

Right now, this fails with no decent workaround:

    package R1;
    use Moose::Role;
    has foo => (is => 'ro');

    package R2;
    use Moose::Role;
    with 'R1';
    requires 'foo';

    package C;
    use Moose;
    with 'R2';

Role attributes really need to be able to participate in role-role combination.
This should also fix "with 'Role1', 'Role2'" being broken when Role1 implements
a method as an accessor and Role2 requires that method, but at least in that
case you can split it into two 'with' statements with minimal loss of
functionality.

### Method modifiers in roles should silently add 'requires' for them

This shouldn't be a functionality change, just a better error message (and
better introspectability). This shouldn't happen if the role already contains a
method by that name, so it'll depend on the previous fix going in (so "has foo
=> (is => 'ro'); around foo => sub { }" doesn't produce a 'requires' entry).

### has +foo in roles

There's no actual reason for this not to work, and it gets asked often enough
that we really should just do it at some point.

### use Sub::Identify instead of doing our own thing with get_code_info

No idea why we stopped using Sub::Identify in the past, but there's no reason
not to do this. We have a bug fix in our version (the isGV_with_GP thing), so
this should be submitted to Sub::Identify first.

## Needs Thought

These are things we think are good ideas, but they need more fleshing out.

### Add overloading support

or at least, don't break existing overloading support

This shouldn't treat the overloading stuff as actual methods, since that's just
an implementation detail, but we should provide an API for add_overload,
get_overload, get_overload_list, etc. In particular, this would allow
namespace::autoclean to not break things.

Also, MooseX::Role::WithOverloading should probably be cored.

This should probably also wait for the metarole unification fix, to avoid the
::WithOverloading stuff being too insane.

### Actual API for metaclass extensions

Right now, the only way to bundle multiple metaclass traits is via
Moose::Exporter. This is unhelpful if you want to apply the extension to a
metaclass object rather than a class you're actually writing. We should come up
with an API for doing this.

### MooseX::NonMoose in core

I think all of the actual issues are solved at this point. The only issue is
the (necessary) implementation weirdness - it sets up multiple inheritance
between the non-Moose class and Moose::Object, and it installs a custom
constructor method at 'extends' time (although perhaps this could be solved by
moving some of the logic back into Moose::Object::new?). Other than that, it
handles everything transparently as far as I can tell.

### Fix attribute and method metaclass compatibility

So i got this wrong when rewriting it last year - right now, metaclass compat
checks the default attribute and method metaclasses, which is wrong. This means
that if a parent class does "use MooseX::FollowPBP", then attributes declared
in a subclass will get PBP-style accessors, which is quite surprising.

On the other hand, sometimes metaclasses might need to be able to say "I'm
going to assume that all of my attributes at least inherit from this custom
class", so we might need to split it into "default specified by the user" and
"default specified by the metaclass" and only do compat checking on the second?
I'm not actually sure this is a valid use case though.

Something that probably should be taken into account though is attributes and
methods that extend existing attributes or methods from a superclass should
inherit the metaclass of the existing one. Also not sure if this is correct,
but something to think about.

### Rename a bunch of the public API methods

Right now the public API is kind of a mess - we have things like `get_method`
vs `find_method_by`_name (you almost always want to use the latter), there
being no `has_method` equivalent that checks superclasses, `get_method_list`
being public but only returning method names, while `_get_local_methods` is
private (returning method objects), and yet neither of those looks at
superclasses, and basically none of this naming follows any kind of consistent
pattern.

What we really need is a consistent and easy to remember API where the method
that people would think to use first is the method that they actually mean.
Something like renaming `find_method_by_name` to `find_method`, and `get_method` to
`find_local_method` or something along those lines.

### Clean up metaclass constructors

There's a _lot_ of different conventions in here. Some things to consider:

* new vs _new
* allowing new( 'name', %args ) vs ( name => 'name', %args )
* Method->wrap vs Method->new

### Move method modifiers out to an external module

Class::Method::Modifiers uses a different method for doing method modifiers,
which I'm not sure why we aren't using in Moose right now. Optionally using
Class::Method::Modifiers::Fast would be even better - it uses Data::Util to
implement XS method modifiers, which could help things a lot.

### Move type constraints out to an external module

There's nothing about our type constraint system that requires being tied to
Moose - it's conceptually an entirely separate system that Moose just happens
to use. Splitting it out into its own thing (that Moose could extend to add
things like role types) would make things conceptually a lot cleaner, and would
let people interested in just the type system have that.

### Merge Class::MOP and Moose

This is a long term goal, but would allow for a lot of things to be cleaned up.
There's a bunch of stuff that's duplicated, and other stuff that's not
implemented as well as it could be (Class::MOP::Method::Wrapped should be a
role, for instance).

### Fix the error system

oh god it's terrible

More specifically, we really want exception objects.

### Moose::Util::TypeConstraints vs Moose::Meta::Type{Coercion,Constraint}

The Util module has _way_ too much functionality. It needs to be
refactored so it's a thin sugar layer on top of the meta API. As it
stands now, it does things like parse type names (and determine if
they're valid), manage the registry, and much more.

### Anything with a _(meta)?class method

Every method that returns a class name needs to become a rw attribute
that can be set via the constructor.

### Make method conflicts in role -> role application silent

Right now this becomes a conflict. We should make this simply ignore the
applied role's method (consumer wins), just like with classes.

Note that this does *not* apply to role summation, where the current behavior
(generates a conflict) is correct.

## Things to contemplate

These are ideas we're not sure about. Prototypes are welcome, but we may never
merge the feature.

### Does applying metaroles really need to reinitialize the metaclass?

Seems like the logic that's actually necessary is already contained in
rebless_instance, and not reinitializing means that existing attributes and
methods won't be blown away when metaroles are applied.

### Do we want to core namespace::autoclean behavior somehow?

This would add Variable::Magic as a required XS dep (not a huge deal at the
moment, since Sub::Name is also a required XS dep, but it'd be nice for Moose
to be able to be pure perl again at some point in the future, and I'm not sure
what the relative chances of Sub::Name vs Variable::Magic making it into core
are). If we enabled it by default, this would also break things for people who
have introduced Moose into legacy-ish systems where roles are faked using
exporters (since those imported methods would be cleaned).

If we decide we want this, we may want to core it as an option first ("use
Moose -clean" or so), and move to making it the default later.

### Should using -excludes with a role add 'requires' for excluded methods?

It seems to make sense, since otherwise you're violating the role's API
contract.

### Moose "strict" mode

use Moose 'strict'; This would allow us to have all sort of expensive tests
which can be turned off in prod.

### Moose::Philosophy.pod

To explain Moose from a very high level

### moosedoc

We certainly have enough meta-information to make pretty complete POD docs.

## TODO test summary

Note that some of these are fairly old, and may not be things we actually want
to do anymore.

### `t/basics/basic_class_setup.t`

Imports aren't automatically cleaned. Need to think about bringing
namespace::autoclean functionality into core.

### `t/bugs/create_anon_recursion.t`

Loading Moose::Meta::Class (or probably a lot of other metaclasses) before
loading Moose or Class::MOP causes issues (the bootstrapping gets confused).

### `t/bugs/handles_foreign_class_bug.t`

There should be a warning when delegated methods override 'new' (and possibly
others?).

### `t/bugs/role_caller.t`

Role methods should be cloned into classes on composition so that using
caller(0) in a role method uses the class's package, not the role's.

### `t/cmop/metaclass_incompatibility.t`

If a child class is created before a parent class, metaclass compatibility
checks won't run on the child when the parent is created, and so the child
could end up with an incompatible metaclass.

### `t/cmop/modify_parent_method.t`

Modifying parent class methods after a child class has already wrapped them
with a method modifier will cause the child class method to retain the original
method that it wrapped, not the new one it was replaced with.

### `t/immutable/inline_close_over.t`

Initializers and custom error classes still close over metaobjects.
Initializers do it because the initializer has to be passed in the attribute
metaobject as a parameter, and custom error classes can't be automatically
inlined.

### `t/metaclasses/moose_exporter_trait_aliases.t`

Renamed imports aren't cleaned on unimport. For instance:

    package Foo;
    use Moose has => { -as => 'my_has' };
    no Moose;
    # Foo still contains my_has

### `t/metaclasses/reinitialize.t`

Special method types can't have method metaroles applied. Applying a method
metarole to a class doesn't apply that role to things like constructors,
accessors, etc.

### `t/roles/compose_overloading.t`

Overload methods aren't composed during role composition (this is detailed
above - Add overloading support).

### `t/roles/method_modifiers.t`

Method modifiers in roles don't support the regex form of method selection.

### `t/roles/role_compose_requires.t`

Accessors for attributes defined in roles don't satisfy role method
requirements (this is detailed above - Attributes in roles need to be able to
participate in role composition).

### `t/todo_tests/exception_reflects_failed_constraint.t`

Type constraint failures should indicate which ancestor constraint failed -
subtype 'Foo', as 'Str', where { length < 5 } should mention Str when passed an
arrayref, but not when passed the string "ArrayRef".

### `t/todo_tests/moose_and_threads.t`

On 5.8, the type constraint name parser isn't thread safe.

### `t/todo_tests/replacing_super_methods.t`

Modifying parent class methods after a child class has already wrapped them
with a override will cause 'super' in the child class to call the original
parent class method, not the one it was overridden with.

### `t/todo_tests/required_role_accessors.t`

Role attribute accessors don't satisfy requires from roles they consume.

### `t/todo_tests/role_insertion_order.t`

Roles don't preserve attribute insertion_order.

### `t/todo_tests/various_role_features.t`

* Role attribute accessors don't satisfy requires from roles they consume.
* Role combination should produce a conflict when one role has an actual method
  and the other role has an accessor.
* Role attribute accessors should not override methods in the class the role is
  applied to.
* Role attribute accessors should be delegated when a class does
  handles => 'Role'.
* Delegating to a role doesn't make $class->does('Role') true.
* Method modifier in a role doesn't create a method requirement.
* Role->meta->has_method('attr_accessor') is false.

### `t/type_constraints/type_names.t`

Type constraint object constructors don't validate the type name provided.

----

## Old todo

Old todo stuff which may be totally out of date.

### DDuncan's Str types

    subtype 'Str'
        => as 'Value'
        => where { Encode::is_utf8( $_[0] ) or $_[0] !~ m/[^0x00-0x7F]/x }
        => optimize_as { defined($_[0]) && !ref($_[0]) };

    subtype 'Blob'
        => as 'Value'
        => where { !Encode::is_utf8( $_[0] ) }
        => optimize_as { defined($_[0]) && !ref($_[0]) };

### type unions

Add support for doing it with Classes which do not have a type constraint yet
created

### type intersections

Mostly just for Roles

### inherited slot specs

'does' can be added to,.. but not changed (need type unions for this)

### proxy attributes

a proxied attribute is an attribute which looks like an attribute, talks like
an attribute, smells like an attribute,.. but if you look behind the
curtain,.. its over there.. in that other object

(... probably be a custom metaclass)

### local coerce

    [13:16]   mst stevan: slight problem with coerce
    [13:16]   mst I only get to declare it once
    [13:17]   mst so if I'm trying to declare it cast-style per-source-class rather than per-target-class
    [13:17]   mst I am extremely screwed
    [13:17]   stevan  yes
    [13:17]   stevan  they are not class specific
    [13:18]   stevan  they are attached to the type constraint itself
    [13:18]   *   stevan ponders anon-coercion-metaobjects
    [13:18]   mst yes, that's fine
    [13:19]   mst but when I declare a class
    [13:19]   mst I want to be able to say "this class coerces to X type via <this>"
    [13:19]   stevan  yeah something like that
    [13:19]   stevan  oh,.. hmm
    [13:20]   stevan  sort of like inflate/deflate?
    [13:20]   stevan  around the accessors?
    [13:25]   *   bluefeet has quit (Remote host closed the connection)
    [13:27]   mst no
    [13:27]   mst nothing like that
    [13:27]   mst like a cast
    [13:31]   mst stevan: $obj->foo($bar); where 'foo' expects a 'Foo' object
    [13:31]   mst stevan: is effectively <Foo>$bar, right?
    [13:32]   mst stevan: I want to be able to say in package Bar
    [13:32]   mst stevan: coerce_to 'Foo' via { ... };
    [13:32]   mst etc.
    [13:53]   stevan  hmm

### add support for locally scoped TC

This would borrow from MooseX::TypeLibrary to prefix the TC with the name
of the package. It would then be accesible from the outside as the fully
scoped name, but the local attributes would use it first. (this would need support
in the registry for this).

### look into sugar extensions

Use roles as sugar layer function providers (ala MooseX::AttributeHelpers). This
would allow custom metaclasses to provide roles to extend the sugar syntax with.

(NOTE: Talk to phaylon a bit more on this)

### allow a switch of some kind to optionally turn TC checking off at runtime

The type checks can get expensive and some people have suggested that allowing
the checks to be turned off would be helpful for deploying into performance
intensive systems. Perhaps this can actually be done as an option to make_immutable?

### misc. minor bits

* make the errors for TCs use ->message
* look into localizing the messages too
* make ANON TCs be lazy, so they can possibly be subsituted for the real thing later
* make ANON TCs more introspectable
* add this ...

        subtype 'Username',
           from 'Str',
          where {     (/[a-z][a-z0-9]+/i or fail('Invalid character(s)'))
                  and (length($_) >= 5   or fail('Too short (less than 5 chars)'))
                }
        on_fail { MyException->throw(value => $_[0], message => $_[1]) };

fail() will just return false unless the call is made via $tc->check_or_fail($value);

* and then something like this:

        subtype Foo => as Bar => where { ... } => scoped => -global;
        subtype Foo => as Bar => where { ... } => scoped => -local;

        # or

        subtype Foo => as Bar => where { ... } => in __PACKAGE__ ;

        # or (not sure if it would be possible)

        my $Foo = subtype Bar => where { ... };

### Deep coercion?

    [17:10]  <autarch> stevan: it should do it if I pass coerce => 1 as part of the attribute definition
    [17:12]  <stevan> autarch: what I am not 100% sure of is how to tell it to deep coerce and when to not
    [17:13]  <stevan> cause a basic coerce is from A to B
    [17:13]  <autarch> hmm
    [17:13]  <stevan> which is valid for collection types too
    [17:13]  <stevan> deep coercion is what you are asking for
    [17:13]  <autarch> yeah
    [17:13]  <stevan> so perhaps we add deep_coerce => 1
    [17:13]  <stevan> which will do it
    [17:13]  <autarch> that's fine for me
    [17:13]  <stevan> k

coerce_deeply => 1 # reads better

### Moose::Meta::TypeConstraint::Parameter{izable,ized}

The relationship between these two classes is very odd. In particular,
this line in Parameterized is insane:

    foreach my $type (Moose::Util::TypeConstraints::get_all_parameterizable_types()) {

Why does it need to loop through all parameterizable types? Shouldn't
it know which parameterizable type it "came from"?