new middleware

[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+

=head3 Support passing Bpdy filehandles directly to your Plack server.

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 properly supportubg chunked encoding when
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.

Please see note below about changes to filehandle support and existing
Plack middleware to aid in back compatibility.

=head3 Distinguish between body null versus undef.

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.

=head3 More Catalyst Middleware

We have started migrating code in Catalyst to equivilent Plack
Middleware when such exists and is correct to do so.  For example we now use
L<Plack::Middleware::ContentLength> to determine content length of a response
when none is provided.  This replaces similar code inlined with L<Catalyst>
The main advantages to doing this is 1) more similar Catalyst core that is 
focused on the Catalyst special sauce, 2) Middleware is more broadly shared
so we benefit from better collaboration with developers outside Catalyst, 3)
In the future you'll be able to change or trim the middleware stack to get
additional performance when you don't need all the checks and constraints.

=head3 Deprecation of Filehandle like objects that do read but not getline

We also deprecated setting the response body to an object that does 'read'
but not 'getline'.  If you are using a custom IO-Handle like object for
response you should verify that 'getline' is supported in your interface.
You will get a first use warning for this error in your logs.  Unless we
here this case is a major issue for people, we will be removing support
in a near future release of Catalyst.  When the code encounters this it
will issue a warning.  You also may run into this issue with L<MogileFS::Client>
which does read but not getline.  For now we will just warn when encountering
such an object and fallback to the previous behavior (where L<Catalyst::Engine>
itself unrolls the filehandle and performs blocking streams).  However
this backcompat will be removed in an upcoming release so you should either
rewrite your custom filehandle objects to support getline or start using the 
middleware that adapts read for getline L<Plack::Middleware::AdaptFilehandleRead>.

=head3 Response->headers become readonly after finalizing

Once the response headers are finalized, trying to change them is not allowed
(in the past you could change them and this would lead to unexpected results).

=head3 Offically deprecation of L<Catalyst::Engine::PSGI>

L<Catalyst::Engine::PSGI> is also officially no longer supported.  We will
no long run test cases against this and can remove backcompat code for it
as deemed necessary for the evolution of the platform.  You should simple
discontinue use of this engine, as L<Catalyst> has been PSGI at the core
for several years.

=head2 Officially deprecate finding the PSGI $env anyplace other than Request

A few early releases of Cataplack had the PSGI $env in L<Catalyst::Engine>.
Code has been maintained here for backcompat reasons.  This is no longer
supported and will be removed in upcoming release, so you should update
your code and / or upgrade to a newer version of L<Catalyst>

=head2 Deprecate setting Response->body after using write/write_fh

Setting $c->res->body to a filehandle after using $c->res->write or
$c->res->write_fh is no longer considered allowed, since we can't send
the filehandle to the underlying Plack handler.  For now we will continue
to support setting body to a simple value since 

=head2 VERSION 5.90053

We are now clarifying the behavior of log, plugins and configuration during
the setup phase.  Since Plugins might require a log during setup, setup_log
must run BEFORE setup_plugins.   This has the unfortunate side effect that
anyone using the popular ConfigLoader plugin will not be able to supply
configuration to custom logs since the configuration is not yet finalized
when setup_log is run (when using ConfigLoader, which is a plugin and is
not loaded until later.)

As a workaround, you can supply custom log configuration directly into
the configuration:

    package MyApp;
    use Catalyst;

    __PACKAGE__->config(
      my_custom_log_info => { %custom_args },
    );

    __PACKAGE__->setup;

If you wish to configure the custom logger differently based on ENV, you can
try:

    package MyApp;

    use Catalyst;
    use Catalyst::Utils;

    __PACKAGE__->config(
      Catalyst::Utils::merge_hashes(
        +{ my_custom_log_info => { %base_custom_args } },
        +{ do __PACKAGE__->path_to( $ENV{WHICH_CONF}."_conf.pl") },
      ),
    );

    __PACKAGE__->setup;

Or create a standalone Configuration class that does the right thing.

Basically if you want to configure a logger via Catalyst global configuration
you can't use ConfigLoader because it will always be loaded too late to be of
any use.  Patches and workaround options welcomed!

=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