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Catalyst::Delta(3pm) User Contributed Perl Documentation Catalyst::Delta(3pm)


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


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

VERSION 5.90105

This version primarily fixed a regression in the way we preserved $c->state which the previous version introduced. Now in the case when you forward to an action, should that action throw an exception it sets state to 0 and is sure that the return value is false. This is to meet expected behavior based on the documentation. If you relied on the last update behavior you may not have regressions but it was thought that we should make the code behave as documented for more than 10 years.

We also changed how we compose the request, response and stats base class. We now compose the base class with any configured traits once at the end of the application setup, rather than for each request. This reduced request overhead when you are composing lots of traits. It possible this may break some code that was adding traits after the application setup was finalized. Please shout out if this actually causes you trouble and we'll do the best to accommodate.

VERSION 5.90102 - 5.90103

A significant change is that we now preserve the value of $c->state from action to following action. This gives you a new way to pass a value between actions in a chain, for example. However any 'auto' actions always have $c->state forced to be set to 0, which is the way its been for a long time, this way an auto action is required to return 1 to pass the match. It also exists to maintain compatibility with anyone that exits an auto action with a detach (which is not a documented way to escape matching, but exists in the wild since it worked as a side effect of the code for a long time).

Additionally, upon $c->detach we also force set state to 0.

Version 5.90102 contains a version of this change but its considered buggy, so that is a version to avoid.

VERSION 5.90100

Support for type constraints in Args and CaptureArgs has been improved. You may now inherit from a base controller that declares type constraints and use roles that declare type constraints. See Catalyst::RouteMatching for more.

You may now. also use a full type constraint namespace instead of importing type constraints into your package namespace.

We changed the way the middleware stash works so that it no longer localizes the PSGI env hashref. This was done to fix bugs where people set PSGI ENV hash keys and found them to disappear in certain cases. It also means that now if a sub applications sets stash variables, that stash will now bubble up to the parent application. This may be a breaking change for you since previous versions of this code did not allow that. A workaround is to explicitly delete stash keys in your sub application before returning control to the parent application.

VERSION 5.90097

Defined how $c->uri_for adds a URI fragment.

We now have a specification for creating URIs with fragments (or HTML anchors). Previously you could do this as a side effect of how we create URIs but this side effect behavior was never documented or tested, and was broken when we introduced default UTF-8 encoding. When creating URIs with fragments please follow the new, supported specification:

    $c->uri_for($action_or_path, \@captures_or_args, @args, \$query, \$fragment);

This will be a breaking change for some codebases, we recommend testing if you are creating URLs with fragments.

NOTE If you are using the alternative:


construction, we do not attempt to encode this and it will make a URL with a fragment of 'baz'.

VERSION 5.90094

Multipart form POST with character set headers

When we did the UTF8 work, we punted on Form POSTs when the POST envelope was multipart and each part had complex headers such as content-types, character sets and so forth. In those cases instead of returning a possibly incorrect value, we returned an object describing the part so that you could figure it out manually. This turned out to be a bad workaround as people did not expect to find that object. So we changed this to try much harder to get a correct value. We still return an object if we fail but we try much harder now. If you used to check for the object you might find that code is no longer needed (although checking for it should not hurt or break anything either).

VERSION 5.90091

'case_sensitive' configuration

At one point in time we allowed you to set a 'case_sensitive' configuration value so that you could find actions by their private names using mixed case. We highly discourage that. If you are using this 'feature' you should be on notice that we plan to remove the code around it in the near future.

VERSION 5.90090+

Type constraints on Args and CaptureArgs.

You may now use a type constraint (using Moose, MooseX::Types or preferably Type::Tiny in your Args or CaptureArgs action attributes. This can be used to restrict the value of the Arg. For example:

    sub myaction :Local Args(Int) { ... }

Would match '.../myaction/5' but not '.../myaction/string'.

When an action (or action chain) has Args (or CaptureArgs) that declare type constraints your arguments to $c->uri_for(...) must match those constraints.

See Catalyst::RouteMatching for more.

Move CatalystX::InjectComponent into core

Catalyst::Utils has a new method 'inject_component' which works the same as the method of the same name in CatalystX::InjectComponent.


New configuration key allows you to inject components directly into your application without any subclasses. For example:

      inject_components => {
        'Controller::Err' => { from_component => 'Local::Controller::Errors' },
        'Model::Zoo' => { from_component => 'Local::Model::Foo' },
        'Model::Foo' => { from_component => 'Local::Model::Foo', roles => ['TestRole'] },
      'Controller::Err' => { a => 100, b=>200, namespace=>'error' },
      'Model::Zoo' => { a => 2 },
      'Model::Foo' => { a => 100 },

Injected components are useful to reduce the amount of nearly empty boilerplate classes you might have, particularly when first starting an application.

Component setup changes.

Previously you could not depend on an application scoped component doing setup_components since components were setup 'in order'. Now all components are first registered and then setup, so you can now reliably use any component doing setup_components.

VERSION 5.90080+

The biggest change in this release is that UTF8 encoding is now enabled by default. So you no longer need any plugins (such as Catalyst::Plugin::Unicode::Encoding) which you can just no go ahead and remove. You also don't need to set the encoding configuration (__PACKAGE__->config(encoding=>'UTF-8')) anymore as well (although its presence hurts nothing).

If this change causes you trouble, you can disable it:


For further information, please see Catalyst::UTF8

But please report bugs. You will find that a number of common Views have been updated for this release (such as Catalyst::View::TT). In all cases that the author is aware of these updates were to fix test cases only. You shouldn't need to update unless you are installing fresh and want tests to pass.

Catalyst::Plugin::Compress was updated to be compatible with this release. You will need to upgrade if you are using this plugin. Catalyst::Upgrading also has details.

A small change is that the configuration setting "using_frontend_proxy" was not doing the right thing if you started your application with "psgi_app" and did not apply the default middleware. This setting is now honored in all the ways an application may be started. This could cause trouble if you are using the configuration value and also adding the proxy middleware manually with a custom application startup. The solution is that you only need the configuration value set, or the middleware manually added (not both).

VERSION 5.90060+

Catalyst::Log object autoflush on by default

Starting in 5.90065, the Catalyst::Log object has 'autoflush' which is on by default. This causes all messages to be written to the log immediately instead of at the end of startup and then at the end of each request. In order to access the old behavior, you must now call:


Deprecate Catalyst::Utils::ensure_class_loaded

Going forward we recommend you use Module::Runtime. In fact we will be converting all uses of Class::Load to Module::Runtime. We will also convert Catalyst::Utils\ensure_class_loaded to be based on Module::Runtime to allow some time for you to update code, however at some future point this method will be removed so you should stop using it now.

Support passing Body 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 supporting 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 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 backwards compatibility.

Distinguish between body null versus undef.

We also now more carefully distinguish 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 Plack::Middleware::BufferedStreaming or report specific problems to the dev team.

More Catalyst Middleware

We have started migrating code in Catalyst to equivalent Plack Middleware when such exists and is correct to do so. For example we now use Plack::Middleware::ContentLength to determine content length of a response when none is provided. This replaces similar code inlined with 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.

Deprecate 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. 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 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 Catalyst::Engine itself unrolls the filehandle and performs blocking streams). However this backwards compatibility 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 Plack::Middleware::AdaptFilehandleRead.

Response->headers become read-only 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).

Officially deprecate Catalyst::Engine::PSGI

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

Officially deprecate finding the PSGI $env anyplace other than Request

A few early releases of Cataplack had the PSGI $env in Catalyst::Engine. Code has been maintained here for backwards compatibility 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 Catalyst

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 this is possible, but at some future release a choice to use streaming indicates that you will do so for the rest of the request.

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;
      my_custom_log_info => { %custom_args },

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

    package MyApp;
    use Catalyst;
    use Catalyst::Utils;
        +{ my_custom_log_info => { %base_custom_args } },
        +{ do __PACKAGE__->path_to( $ENV{WHICH_CONF}."") },

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!

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 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 Plack, and automatically gains support for any web server which a 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 Catalyst::Upgrading for notes about upgrading, especially if you are using an unusual deployment method.

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

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:

This is now deprecated, see Catalyst::Upgrading.
Has been updated to not produce deprecation warnings, upgrade recommended.
Has been updated to fix failing tests (although older versions still function perfectly with this version of Catalyst).
Has been updated to fix failing tests (although older versions still function perfectly with this version of Catalyst).
Has been updated to fix failing tests (although older versions still function perfectly with this version of Catalyst).


VERSION 5.8XXXX 'catamoose'


Please see 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:

::[MVC]:: style naming scheme has been deprecated and will warn
__PACKAGE__->mk_accessors() is supported for backwards compatibility only, use Moose attributes instead in new code.

New features



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

$c->uri_for_action method.

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


Log levels have been made additive.



  • New print method which prints @data to the output stream, separated by $,. This lets you pass the response object to functions that want to write to an IO::Handle.
  • Added code method as an alias for "$res->status"

Consequences of the Moose back end

  • 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.
  • Many reusable extensions which would previously have been plugins or base classes are better implemented as Moose roles.
  • 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.
  • 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.
  • Refactored capturing of $app from Catalyst::Controller into Catalyst::Component::ApplicationAttribute for easier reuse in other components.
  • Your application class is forced to become immutable at the end of compilation.

Bug fixes

  • Don't ignore SIGCHLD while handling requests with the development server, so that system() and other ways of creating child processes work as expected.
  • Fixes for FastCGI when used with IIS 6.0
  • Fix a bug in uri_for which could cause it to generate paths with multiple slashes in them.
  • Fix a bug in Catalyst::Stats, stopping garbage being inserted into the stats if a user calls begin => but no end
2023-09-28 perl v5.36.0