remove custom catalyst code and use Plack Middleware instead

[catagits/Catalyst-Runtime.git] / lib / Catalyst / Delta.pod

=head1 NAME

Catalyst::Delta - Overview of changes between versions of Catalyst

=head1 DESCRIPTION

This is an overview of the user-visible changes to Catalyst between major
Catalyst releases.

=head2 VERSION 5.90060+

We changed the way we return body content (from response) to whatever
Plack handler you are using (Starman, FastCGI, etc.)  We no longer
always use the streaming interface for the cases when the body is a
simple scalar, object or filehandle like.  In those cases we now just
pass the simple response on to the plack handler.  This might lead to
some minor differences in how streaming is handled.  For example, you
might notice that streaming starts using chunked encoding when running
on a server that supports that, or that previously missing headers
(possible content-length) might appear suddenly correct.  Also, if you
are using middleware like L<Plack::Middleware::XSendfile> and are using
a filehandle that sets a readable path, your server might now correctly
handle the file (rather than as before where Catalyst would stream it
very likely very slowly).

In other words, some things might be meaninglessly different and some
things that were broken codewise but worked because of Catalyst being
incorrect might suddenly be really broken.  The behavior is now more
correct in that Catalyst plays better with features that Plack offers
but if you are making heavy use of the streaming interface there could
be some differences so you should test carefully (this is probably not
the vast majority of people).  In particular if you are developing
using one server but deploying using a different one, differences in
what those server do with streaming should be noted.

We also now more carefully distingush the different between a body set
to '' and a body that is undef.  This might lead to situations where
again you'll get a content-length were you didn't get one before or
where a supporting server will start chunking output.  If this is an
issue you can apply the middleware L<Plack::Middleware::BufferedStreaming>
or report specific problems to the dev team.

Also, we have started migrating code in Catalyst to equivilent Plack
Middleware when such exists and is correct to do so. 

=head2 VERSION 5.9XXXX 'cataplack'

The Catalyst::Engine sub-classes have all been removed and deprecated,
to be replaced with Plack handlers.

Plack is an implementation of the L<PSGI> specification, which is
a standard interface between web servers and application frameworks.

This should be no different for developers, and you should not have to
migrate your applications unless you are using a custom engine already.

This change benefits Catalyst significantly by reducing the amount of
code inside the framework, and means that the framework gets upstream
bug fixes in L<Plack>, and automatically gains support for any web server
which a L<PSGI> compliant handler is written for.

It also allows you more flexibility with your application, and allows
the use of cross web framework 'middleware'.

Developers are recommended to read L<Catalyst::Upgrading> for notes about
upgrading, especially if you are using an unusual deployment method.

Documentation for how to take advantage of L<PSGI> can be found in
L<Catalyst::PSGI>, and information about deploying your application
has been moved to L<Catalyst::Manual::Deployment>.

=head3 Updated modules:

A number of modules have been updated to pass their tests or not
produce deprecation warnings with the latest version of Catalyst.
It is recommended that you upgrade any of these that you are using
after installing this version of Catalyst.

These extensions are:

=over

=item L<Catalyst::Engine::HTTP::Prefork>

This is now deprecated, see L<Catalyst::Upgrading>.

=item L<Test::WWW::Mechanize::Catalyst>

Has been updated to not produce deprecation warnings, upgrade recommended.

=item Catalyst::ActionRole::ACL

Has been updated to fix failing tests (although older versions still
function perfectly with this version of Catalyst).

=item Catalyst::Plugin::Session::Store::DBIC

Has been updated to fix failing tests (although older versions still
function perfectly with this version of Catalyst).

=item Catalyst::Plugin::Authentication

Has been updated to fix failing tests (although older versions still
function perfectly with this version of Catalyst).

=back

=head1 PREVIOUS VERSIONS

=head2 VERSION 5.8XXXX 'catamoose'

=head3 Deprecations

Please see L<Catalyst::Upgrading> for a full description of how changes in the
framework may affect your application.

Below is a brief list of features which have been deprecated in this release:

=over

=item ::[MVC]:: style naming scheme has been deprecated and will warn

=item NEXT is deprecated for all applications and components, use MRO::Compat

=item Dispatcher methods which are an implementation detail made private, public versions now warn.

=item MyApp->plugin method is deprecated, use L<Catalyst::Model::Adaptor> instead.

=item __PACKAGE__->mk_accessors() is supported for backward compatibility only, use Moose attributes instead in new code.

=item Use of Catalyst::Base now warns

=back

=head3 New features

=head3 Dispatcher

=over

=item Fix forwarding to Catalyst::Action objects.

=item Add the dispatch_type method

=back

=head3 Restarter

The development server restarter has been improved to be compatible with
immutable Moose classes, and also to optionally use 
L<B::Hooks::OP::Check::StashChange> to handle more complex application layouts
correctly.

=head3 $c->uri_for_action method.

Give a private path to the Catalyst action you want to create a URI for.

=head3 Logging

Log levels have been made additive.

=head3 L<Catalyst::Test>

=over

=item Change to use L<Sub::Exporter>.

=item Support mocking multiple virtual hosts

=item New methods like action_ok and action_redirect to write more compact tests

=back

=head3 Catalyst::Response

=over

=item *

New print method which prints @data to the output stream, separated by $,.  
This lets you pass the response object to functions that want to write to an 
L<IO::Handle>.

=item *

Added code method as an alias for C<< $res->status >>

=back

=head3 Consequences of the Moose back end

=over

=item *

Components are fully compatible with Moose, and all Moose features, such as
method modifiers, attributes, roles, BUILD and BUILDARGS methods are fully
supported and may be used in components and applications.

=item *

Many reusable extensions which would previously have been plugins or base 
classes are better implemented as Moose roles.

=item *

L<MooseX::MethodAttributes::Role::AttrContainer::Inheritable> is used to contain action
attributes. This means that attributes are represented in the MOP, and
decouples action creation from attributes.

=item *

There is a reasonable API in Catalyst::Controller for working with
and registering actions, allowing a controller sub-class to replace
subroutine attributes for action declarations with an alternate
syntax.

=item *

Refactored capturing of $app from L<Catalyst::Controller> into
L<Catalyst::Component::ApplicationAttribute> for easier reuse in other
components.

=item *

Your application class is forced to become immutable at the end of compilation.

=back

=head3 Bug fixes

=over

=item *

Don't ignore SIGCHLD while handling requests with the development server, so that
system() and other ways of creating child processes work as expected.

=item *

Fixes for FastCGI when used with IIS 6.0

=item *

Fix a bug in uri_for which could cause it to generate paths with multiple 
slashes in them.

=item *

Fix a bug in Catalyst::Stats, stopping garbage being inserted into
the stats if a user calls begin => but no end

=back