Cataly...grading(3pm)

📦

version 5.90132 · 6 versions

5.90132 · debian trixie, ubuntu resolute, ubuntu stonking (latest)
5.90132 · fedora 43
5.90128 · ubuntu jammy
5.90132 · fedora 44
5.90131 · ubuntu noble
5.90130 · debian bookworm

, in debian trixie, ubuntu resolute, ubuntu stonking

✨ Catalyst::Upgrading 💅 — the glow-up guide ✨

Cataly...grading(3pm) · User Contributed Perl Documentation · Cataly...grading(3pm)

okay bestie so this is literally the manual page for Catalyst::Upgrading — Instructions for upgrading to the latest Catalyst. yes the header is out here being all mysterious with the Cataly...grading(3pm) thing, that's just the short name, don't worry about it 🫶

💖 NAME 💖

Catalyst::Upgrading — Instructions for upgrading to the latest Catalyst. that's it. that's the name. iconic behavior honestly 👑

🌸 Upgrading to Catalyst 5.90121 🌸

A new log_stats method has been added. this only affects subclasses that have a method with this name added — so if that's not you, you can just vibe past this one, no cap.

🦋 Upgrading to Catalyst 5.90100 🦋

okay so we changed the way the middleware stash works, and the whole point was that it no longer localizes the PSGI env hashref. why? because we were fixing bugs where people set PSGI ENV hash keys and then found them just disappearing in certain cases 😭 which is so rude.

but here's the tea, and it might be a little spicy for you: it also means that now, if a sub application 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. 🙈

workaround if you're not feeling it: explicitly delete stash keys in your sub application before returning control to the parent application. slay, problem solved 💅

🧚 Upgrading to Catalyst 5.90097 🧚

so in older versions of Catalyst, one could construct a URI with a fragment (such as https://localhost/foo/bar#fragment) by using a '#' in the path or final argument, for example:

$c->uri_for($action, 'foo#fragment');

this behavior was never documented and would break if using the Unicode plugin, or when adding a query to the arguments:

$c->uri_for($action, 'foo#fragment', +{ a=>1, b=>2});

would define a fragment like "#fragment?a=1&b=2". yeah. not great, bestie. 💀

When we introduced UTF-8 encoding by default in Catalyst 5.9008x this side effect behavior was broken since we started encoding the '#' when it was part of the URI path.

In version 5.90095 and 5.90096 we attempted to fix this, but all we managed to do was break people with URIs that included '#' as part of the path data, when it was not expected to be a fragment delimiter. not our finest era, ngl 😭

In general Catalyst prefers an explicit specification rather than relying on side effects or domain specific mini languages. so as a result we are now defining how to set a fragment for a URI via ->uri_for:

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

WARNING bestie: if you are relying on the previous side effect behavior, your URLs will now encode the '#' delimiter, which is going to be a breaking change for you. you need to alter your code to match the new specification, or modify uri_for for your local case. patches to solve this are very welcomed, as long as they don't break existing test cases. 🫶

NOTE — if you are using the string form of the first argument:

$c->uri_for('/foo/bar#baz')

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

💜 Upgrading to Catalyst 5.90095 💜

the method "last_error" in "Catalyst" was actually returning the first error. 😭 like, embarrassing. this has been fixed but there is a small chance it could be a breaking issue for you.

if this gives you trouble, changing to "shift_errors" is the easiest workaround (although that does modify the error stack, so if you are relying on that not being changed you should try something like @{$c->errors}[-1] instead).

since this method is relatively new and the cases when the error stack actually has more than one error in it are few, we feel the exposure is very low, but bug reports are very welcomed. tell us everything 🎀

🌈 Upgrading to Catalyst 5.90090 🌈

okay this one is a whole glow-up, buckle up.

Catalyst::Utils has a new method 'inject_component' which works the same as the method of the same name in CatalystX::InjectComponent. you should start converting any use of the non core method in your code as future changes to Catalyst will be synchronized to the core method first. we reserve the right to cease support of the non core version should we reach a point in time where it cannot be properly supported as an external module. luckily this should be a trivial search and replace ✨

change all occurrences of:

CatalystX::InjectComponent->inject(...)

into:

Catalyst::Utils::inject_component(...)

and we expect everything to work the same (we'd consider it not working the same to be a bug, and please report it.) 🐛

We also cored features from CatalystX::RoleApplicator to compose a role into the request, response and stats classes. the main difference is that with CatalystX::RoleApplicator you did:

package MyApp;

use Catalyst;
use CatalystX::RoleApplicator;

__PACKAGE__->apply_request_class_roles(
  qw/My::Request::Role Other::Request::Role/);

Whereas now we have three class attributes — 'request_class_traits', 'response_class_traits' and 'stats_class_traits' — so you use like this (note this value is an ArrayRef):

package MyApp;

use Catalyst;

__PACKAGE__->request_class_traits([qw/
  My::Request::Role
  Other::Request::Role/]);

(And the same for response_class_traits and stats_class_traits. We left off the traits for Engine, since that class does a lot less nowadays, and dispatcher. If you used those and can share a use case, we'd be likely to support them. 👀)

Lastly, we have some of the feature from CatalystX::ComponentsFromConfig in core. this should mostly work the same way in core, except for now the core version does not create an automatic base wrapper class for your configured components (it requires these to be catalyst components and injects them directly. So if you make heavy use of custom base classes in CatalystX::ComponentsFromConfig you might need a bit of work to use the core version (although there is no reason to stop using CatalystX::ComponentsFromConfig since it should continue to work fine and we'd consider issues with it to be bugs). here's one way to map from CatalystX::ComponentsFromConfig to core:

In CatalystX::ComponentsFromConfig:

MyApp->config(
  'Model::MyClass' => {
      class => 'MyClass',
      args => { %args },

  });

and now in core:

MyApp->config(
  inject_components => {
    'Model::MyClass' => { from_component => 'My::Class' },
  },
  'Model::MyClass' => {
    %args
  },
);

Although the core behavior requires more code, it better separates concerns as well as plays more into core Catalyst expectations of how configuration should look. ✨

Also we added a new develop console mode only warning when you call a component with arguments that don't expect or do anything meaningful with those args. its possible if you are logging debug mode in production (please don't... 😭) this could add verbosity to those logs if you also happen to be calling for components and passing pointless arguments. we added this warning to help people not make this error and to better understand the component resolution flow. 🫶

🦋 Upgrading to Catalyst 5.90085 🦋

okay bestie so in this version we made a tiny little change to Chained Dispatching, but it's the kind of tiny change that has OPINIONS. Here's the tea: when two or more actions all have the same path specification AND they all have Args(0), we now break the tie by choosing the last action defined, not the first one defined. Why? To normalize Chaining to follow the rule of "longest Path wins, and when several actions match the same Path specification we choose the last defined." ✨ Previously Args(0) was hard coded to be a special case where the first action defined would match (which — plot twist — is not what happens when Args is not zero).

So yeah, this could be a breaking change for you 😭 if you had used action roles (custom or otherwise) to add extra matching rules to differentiate between several Args(0) actions that share the same root action chain. For example, if you have code now like this:

    sub check_default :Chained(/) CaptureArgs(0) { ... }

      sub default_get :Chained('check_default') PathPart('') Args(0) GET {
          pop->res->body('get3');
      }

      sub default_post :Chained('check_default') PathPart('') Args(0) POST {
          pop->res->body('post3');
      }

      sub chain_default :Chained('check_default') PathPart('') Args(0) {
          pop->res->body('chain_default');
      }

The way that chaining worked previously is that when two or more equal actions can match, the 'top' one wins. So if the request is GET .../check_default BOTH actions default_get AND chain_default would match. To break the tie in the case when Args is 0, we'd previously take the 'top' (or first defined) action. Unfortunately this treatment of Args(0) is a special case. In all other cases we choose the 'last defined' action to break a tie. So this version of Catalyst changed the dispatcher to make Args(0) no longer a special case for breaking ties. This means that the above code must now become:

    sub check_default :Chained(/) CaptureArgs(0) { ... }

      sub chain_default :Chained('check_default') PathPart('') Args(0) {
          pop->res->body('chain_default');
      }

      sub default_get :Chained('check_default') PathPart('') Args(0) GET {
          pop->res->body('get3');
      }

      sub default_post :Chained('check_default') PathPart('') Args(0) POST {
          pop->res->body('post3');
      }

If we want it to work as expected (for example we we GET to match default_get and POST to match default_post and any other http Method to match chain_default). 🫶

In other words Arg(0) and chained actions must now follow the normal rule where in a tie the last defined action wins and you should place all your less defined or 'catch all' actions first. 🌸

If this causes you trouble and you can't fix your code to conform, you may set the application configuration setting use_chained_args_0_special_case to true and that will revert your code to the previous behavior. (yesss, a lil escape hatch, we love to see it 💅)

🌈 More backwards compatibility options with UTF-8 changes 🌈

In order to give better backwards compatibility with the 5.90080+ UTF-8 changes we've added several configuration options around control of how we try to decode your URL keywords / query parameters. It's giving ✨options✨.

💖 `do_not_decode_query`

If true, then do not try to character decode any wide characters in your request URL query or keywords. Most readings of the relevant specifications suggest these should be UTF-* encoded, which is the default that Catalyst will use, however if you are creating a lot of URLs manually or have external evil clients, this might cause you trouble. If you find the changes introduced in Catalyst version 5.90080+ break some of your query code, you may disable the UTF-8 decoding globally using this configuration.

This setting takes precedence over default_query_encoding and decode_query_using_global_encoding. 👑

💖 `default_query_encoding`

By default we decode query and keywords in your request URL using UTF-8, which is our reading of the relevant specifications. This setting allows one to specify a fixed value for how to decode your query. You might need this if you are doing a lot of custom encoding of your URLs and not using UTF-8.

This setting take precedence over decode_query_using_global_encoding.

💖 `decode_query_using_global_encoding`

Setting this to true will default your query decoding to whatever your general global encoding is (the default is UTF-8).

🌟 Upgrading to Catalyst 5.90080 🌟

UTF8 encoding is now default, no cap. For temporary backwards compatibility, if this change is causing you trouble, you can disable it by setting the application configuration option to undef:

    MyApp->config(encoding => undef);

But please consider this a temporary measure since it is the intention that UTF8 is enabled going forwards and the expectation is that other ecosystem projects will assume this as well. At some point you application will not correctly function without this setting. ⚠️

As of 5.90084 we've added two additional configuration flags for more selective control over some encoding changes: skip_body_param_unicode_decoding and skip_complex_post_part_handling. You may use these to more selectively disable new features while you are seeking a long term fix. Please review CONFIGURATION in Catalyst. 🎀

For further information, please see Catalyst::UTF8. 🦋

A number of projects in the wider ecosystem required minor updates to be able to work correctly. Here's the known list, bestie, screenshot it:

Catalyst::View::TT
Catalyst::View::Mason
Catalyst::View::HTML::Mason
Catalyst::View::Xslate
Test::WWW::Mechanize::Catalyst

You will need to update to modern versions in most cases, although quite a few of these only needed minor test case and documentation changes so you will need to review the changelog of each one that is relevant to you to determine your true upgrade needs. 📝

🌸 Upgrading to Catalyst 5.90060 🌸

Starting in the v5.90059_001 development release, the regexp dispatch type is no longer automatically included as a dependency. If you are still using this dispatch type, you need to add Catalyst::DispatchType::Regex into your build system.

The standalone distribution of Regexp will be supported for the time being, but should we find that supporting it prevents us from moving Catalyst forward in necessary ways, we reserve the right to drop that support. It is highly recommended that you use this last stage of deprecation to change your code. 👀

💅 Upgrading to Catalyst 5.90040 💅

✨ `Catalyst::Plugin::Unicode::Encoding` is now core ✨

The previously stand alone Unicode support module Catalyst::Plugin::Unicode::Encoding has been brought into core as a default plugin. Going forward, all you need is to add a configuration setting for the encoding type. For example:

    package Myapp::Web;

    use Catalyst;

    __PACKAGE__->config( encoding => 'UTF-8' );

Please note that this is different from the old stand alone plugin which applied "UTF-8" encoding by default (that is, if you did not set an explicit "encoding" configuration value, it assumed you wanted UTF-8). In order to preserve backwards compatibility you will need to explicitly turn it on via the configuration setting. THIS MIGHT CHANGE IN THE FUTURE, so please consider starting to test your application with proper UTF-8 support and remove all those crappy hacks you munged into the code because you didn't know the Plugin existed :) 💀

For people that are using the Plugin, you will note a startup warning suggesting that you can remove it from the plugin list. When you do so, please remember to add the configuration setting, since you can no longer rely on the default being UTF-8. We'll add it for you if you continue to use the stand alone plugin and we detect this, but this backwards compatibility shim will likely be removed in a few releases (trying to clean up the codebase after all).

If you have trouble with any of this, please bring it to the attention of the Catalyst maintainer group. 🫶

🌈 basic async and event loop support 🌈

This version of Catalyst offers some support for using AnyEvent and IO::Async event loops in your application. These changes should work fine for most applications however if you are already trying to perform some streaming, minor changes in this area of the code might affect your functionality. Please see Catalyst::Response\write_fh for more and for a basic example.

We consider this feature experimental. We will try not to break it, but we reserve the right to make necessary changes to fix major issues that people run into when the use this functionality in the wild. 🔥

👑 Upgrading to Catalyst 5.90030 👑

Regex dispatch type is deprecated. ⚠️

The Regex dispatchtype (Catalyst::DispatchType::Regex) has been deprecated.

You are encouraged to move your application to Chained dispatch (Catalyst::DispatchType::Chained).

If you cannot do so, please add a dependency to Catalyst::DispatchType::Regex to your application's Makefile.PL. 🎀

✨ Upgrading to Catalyst 5.9 ✨

okay so this one is THE big one, bestie. the whole game changed here. 💥

the major glow-up: Plack, a toolkit for using the PSGI specification, now replaces most of the subclasses of Catalyst::Engine. if you're using one of the standard subclasses of Catalyst::Engine, this should be a super straightforward upgrade for you, fr. it was literally a design goal for this release to preserve as much backwards compatibility as possible. 👑

BUT. and this is a real but: since Plack is different from Catalyst::Engine, it is possible that differences exist for edge cases. so the recommendation is that you take care with this upgrade, and that testing should be greater than would be the case with a minor point update. please let the Catalyst developers know about any problems so they can fix them and incorporate tests. 🫶

it is highly recommended that you become familiar with the Plack ecosystem and documentation. being able to take advantage of Plack development and middleware is a major bonus to this upgrade. documentation about how to take advantage of Plack::Middleware by writing your own .psgi file lives in Catalyst::PSGI. 📚

if you have created a custom subclass of <Catalyst:Engine>, you will need to convert it to be a subclass of Plack::Handler.

if you are using the Plack engine, Catalyst::Engine::PSGI, this new release supersedes that code.

if you are using a subclass of Catalyst::Engine that is aimed at nonstandard or internal/testing uses, such as Catalyst::Engine::Embeddable, you should still be able to continue using that engine. 😌

advice for specific subclasses of Catalyst::Engine follows:

🏎️ Upgrading the FastCGI Engine

no upgrade needed if your myapp_fastcgi.pl script is already upgraded to use Catalyst::Script::FastCGI. that's it, that's the section, slay. 💅

🌐 Upgrading the mod_perl / Apache Engines

the engines built upon the various iterations of mod_perl — Catalyst::Engine::Apache::MP13 (for mod_perl 1, and Apache 1.x) and Catalyst::Engine::Apache2::MP20 (for mod_perl 2, and Apache 2.x) — should be seamless upgrades and will work using Plack::Handler::Apache1 or Plack::Handler::Apache2 as required. ✨

Catalyst::Engine::Apache2::MP19, however, is no longer supported, because Plack does not support mod_perl version 1.99. this is unlikely to be a problem for anyone, as 1.99 was a brief beta-test release for mod_perl 2, and all users of mod_perl 1.99 are encouraged to upgrade to a supported release of Apache 2 and mod_perl 2. 💀 (rip 1.99, you were a beta)

🖥️ Upgrading the HTTP Engine

the default development server that comes with the Catalyst distribution should continue to work as expected with no changes, as long as your myapp_server script is upgraded to use Catalyst::Script::HTTP. easy peasy. 🍓

🐌 Upgrading the CGI Engine

if you were using Catalyst::Engine::CGI there is no upgrade needed if your myapp_cgi.pl script is already upgraded to use Catalyst::Script::CGI. ✅

🔁 Upgrading Catalyst::Engine::HTTP::Prefork

if you were using Catalyst::Engine::HTTP::Prefork then Starman is automatically loaded. you should (at least) change your Makefile.PL to depend on Starman.

you can regenerate your myapp_server.pl script with catalyst.pl and implement a MyApp::Script::Server class that looks like this:

package MyApp::Script::Server;
use Moose;
use namespace::autoclean;

extends 'CatalystX::Script::Server::Starman';

1;

this takes advantage of the new script system, and will add a number of options to the standard server script as extra options are added by Starman. 👑

more information about these options can be seen at "SYNOPSIS" in CatalystX::Script::Server::Starman.

an alternate route to implement this functionality is to write a simple .psgi file for your application, and then use the plackup utility to start the server. 🌈

🧬 Upgrading the PSGI Engine

if you were using Catalyst::Engine::PSGI, this new release supersedes this engine in supporting Plack. by default the Engine is now always Plack. as a result, you can remove the dependency on Catalyst::Engine::PSGI in your Makefile.PL. 🗑️

applications that were using Catalyst::Engine::PSGI previously should entirely continue to work in this release with no changes. no cap.

however, if you have an app.psgi script, then you no longer need to specify the PSGI engine. instead, the Catalyst application class now has a new method psgi_app which returns a PSGI compatible coderef which you can wrap in the middleware of your choice. 💖

Catalyst will use the .psgi for your application if it is located in the home directory of the application.

for example, if you were using Catalyst::Engine::PSGI in the past, you will have written (or generated) a script/myapp.psgi file similar to this one:

use Plack::Builder;
use MyCatalytApp;

MyCatalystApp->setup_engine('PSGI');

builder {
    enable ... # enable your desired middleware
    sub { MyCatalystApp->run(@_) };
};

instead, you now say:

use Plack::Builder;
use MyCatalystApp;

builder {
    enable ... #enable your desired middleware
    MyCatalystApp->psgi_app;
};

in the simplest case:

MyCatalystApp->setup_engine('PSGI');
my $app = sub { MyCatalystApp->run(@_) }

becomes

my $app = MyCatalystApp->psgi_app(@_);

NOT:

my $app = sub { MyCatalystApp->psgi_app(@_) };
# If you make ^^ this mistake, your app won't work, and will confuse the hell out of you!

bestie I am BEGGING you, do not wrap psgi_app in an extra sub. it will not work and it will confuse the hell out of you. 😭 that's not me being dramatic, that's literally the original warning.

you can now move script/myapp.psgi to myapp.psgi, and the built-in Catalyst scripts and your test suite will start using your .psgi file. 🎀

NOTE: if you rename your .psgi file without these modifications, then any tests run via Catalyst::Test will not be compatible with the new release, and will result in the development server starting, rather than the expected test running. 💀

NOTE: if you are directly accessing $c->req->env to get the PSGI environment then this accessor is moved to $c->engine->env, you will need to update your code. 🚨

💔 Engines which are known to be broken

the following engines DO NOT work as of Catalyst version 5.9. the core team will be happy to work with the developers and/or users of these engines to help them port to the new Plack/Engine system, but for now, applications which are currently using these engines WILL NOT run without modification to the engine code. 😬

Catalyst::Engine::Wx
Catalyst::Engine::Zeus
Catalyst::Engine::JobQueue::POE
Catalyst::Engine::XMPP2
Catalyst::Engine::SCGI

❓ Engines with unknown status

the following engines are untested or have unknown compatibility. reports are highly encouraged:

Catalyst::Engine::Mojo
Catalyst::Engine::Server (marked as Deprecated)
Catalyst::Engine::HTTP::POE (marked as Deprecated)

🎁 Plack functionality

see Catalyst::PSGI. go read it, it's giving main character energy. 📖

🧪 Tests in 5.9

tests should generally work the same in Catalyst 5.9, but there are some differences. 👀

previously, if using Catalyst::Test and doing local requests (against a local server), if the application threw an exception then this exception propagated into the test.

this behavior has been removed, and now a 500 response will be returned to the test. this change standardizes behavior, so that local test requests behave similarly to remote requests. ✨

🌸 Upgrading to Catalyst 5.80 🌸

most applications and plugins should run unaltered on Catalyst 5.80. 🎉

however, a lot of refactoring work has taken place, and several changes have been made which could cause incompatibilities. if your application or plugin is using deprecated code, or relying on side effects, then you could have issues upgrading to this release. 🙈

most issues found with existing components have been easy to solve. this document provides a complete description of behavior changes which may cause compatibility issues, and of new Catalyst warnings which might be unclear.

if you think you have found an upgrade-related issue which is not covered in this document, please email the Catalyst list to discuss the problem. 📧

🦋 Moose features

🎭 Application class roles

you can only apply method modifiers after the application's ->setup method has been called. this means that modifiers will not work with methods run during the call to ->setup. 💅

see Catalyst::Manual::ExtendingCatalyst for more information about using Moose in your applications.

🎬 Controller actions in Moose roles

you can use MooseX::MethodAttributes::Role if you want to declare actions inside Moose roles. iconic, honestly.

🧩 Using Moose in Components

the correct way to use Moose in a component in a both forward and backwards compatible way is:

package TestApp::Controller::Root;
use Moose;
BEGIN { extends 'Catalyst::Component' }; # Or ::Controller, or whatever

see "Components which inherit from Moose::Object before Catalyst::Component".

🫶 Known backwards compatibility breakages

okay so this is the part where we gently hold your hand through the glow-up casualties 💀 nothing here is a surprise jump-scare, it's all stuff that genuinely changed, and every single one of these has a fix. take a breath, bestie, we got you.

🙈 Applications in a single file

Your apps have to live in their own file, and they have to be loaded at compile time. no cap. This one generally only bites the tests of CPAN distributions. Your app will straight up fail if you try to define an application inline inside a block, then use plugins that supply a new method, and then use that application later on in tests within the same file.

Why? Because Catalyst is inlining a new method onto your application class so it can vibe with Moose. The method it uses to do that changed in 5.80004, specifically to avoid the possibility of reporting an 'Unknown Error' if your application failed to compile. so like, it's for your own good 🥺

💀 Issues with Class::C3

Catalyst 5.80 uses the Algorithm::C3 method dispatch order. It's built into Perl 5.10, and it arrives via Class::C3 for Perl 5.8. This replaces NEXT with Class::C3::Adopt::NEXT, which forces every component to resolve methods using C3 instead of the unpredictable dispatch order of NEXT.

How does this show up? Your application just refuses to start, with an error message about having a non-linear @ISA. iconic behaviour, honestly.

The Catalyst plugin that causes this the most is Catalyst::Plugin::Session::Store::FastMmap — if you're using it and seeing issues, please upgrade your plugins, because it's been fixed 🎀 Also note that Makefile.PL in the distribution will warn about known incompatible components.

But it can also be your own application, and the only solution there is to go through each base class of the class the error was reported against until you find the ones in conflict, and resolve them. tedious but slay.

To generate a linear @ISA, the list of superclasses for each class has to be resolvable using the C3 algorithm. Unfortunately, when superclasses get used as mixins (to add functionality used in your class) and with multiple inheritance, it is so easy to get this wrong.

Most common case, right here:

package Component1; # Note, this is the common case
use base qw/Class::Accessor::Fast Class::Data::Inheritable/;

package Component2; # Accidentally saying it this way causes a failure
use base qw/Class::Data::Inheritable Class::Accessor::Fast/;

package GoesBang;
use base qw/Component1 Component2/;

Any situation like this will cause your application to fail to start. yes, even if it looks fine. it is not fine.

For additional documentation about this issue, and how to resolve it, see Class::C3::Adopt::NEXT.

🦋 Components which inherit from Moose::Object before Catalyst::Component

Moose components that say this:

package TestApp::Controller::Example;
use Moose;
extends qw/Moose::Object Catalyst::Component/;

— trying to use the constructor provided by Moose — will not work with Catalyst 5.80, even if it worked before (if you did some hacks with the BUILDARGS method). That's because Catalyst::Component inherits from Moose::Object, and so @ISA fails to linearize. rip 🪦

The correct way to use Moose in a component, in a way that's both forward and backwards compatible, is:

package TestApp::Controller::Root;
use Moose;
BEGIN { extends 'Catalyst::Component' }; # Or ::Controller, or whatever

Note that the extends declaration needs to occur in a begin block for attributes to operate correctly. do not skip the begin block. it matters 💅

This way you don't inherit directly from Moose::Object yourself. Having components which do not inherit their constructor from Catalyst::Component is unsupported, and has never been recommended — so you're on your own if you're using this technique. You'll need to detect the version of Catalyst your application is running and deal with it appropriately.

You also don't get the Moose::Object constructor, which means attribute initialization will not work as normally expected. If you want to use Moose attributes, they need to be made lazy to correctly initialize.

Note that this only applies if your component needs to maintain component backwards compatibility for Catalyst versions before 5.71001 — in 5.71001 attributes work as expected, and the BUILD method is called normally (although BUILDARGS is not).

If you depend on Catalyst 5.8, then all Moose features work as expected. periodt ✨

You'll also see this issue if you do the following:

package TestApp::Controller::Example;
use Moose;
use base 'Catalyst::Controller';

because use base appends to @ISA. rude, honestly.

💜 `use Moose` in MyApp

Similar to the above, this will also fail:

package MyApp;
use Moose;
use Catalyst qw/
  ConfigLoader
/;
__PACKAGE__->setup;

If you need to use Moose in your application class (e.g. for method modifiers and such), then the correct technique is:

package MyApp;
use Moose;
use Catalyst;

extends 'Catalyst';

__PACKAGE__->config( name => 'MyApp' );
__PACKAGE__->setup(qw/
    ConfigLoader
/);

🌸 Anonymous closures installed directly into the symbol table

If you have any code that installs anonymous subroutine references directly into the symbol table, you may encounter breakages. The simplest solution is to use Sub::Name to name the subroutine. Example:

# Original code, likely to break:
my $full_method_name = join('::', $package_name, $method_name);
*$full_method_name = sub { ... };

# Fixed Code
use Sub::Name 'subname';
my $full_method_name = join('::',$package_name, $method_name);
*$full_method_name = subname $full_method_name, sub { ... };

Additionally, you can take advantage of Catalyst's use of Class::MOP and install the closure using the appropriate metaclass. Example:

use Class::MOP;
my $metaclass = Moose::Meta::Class->initialize($package_name);
$metaclass->add_method($method_name => sub { ... });

🎀 Hooking into application setup

To execute code during application start-up, this snippet in MyApp.pm used to work:

sub setup {
    my ($class, @args) = @_;
    $class->NEXT::setup(@args);
    ... # things to do after the actual setup
}

With Catalyst 5.80 this won't work anymore, because Catalyst no longer uses NEXT.pm for method resolution. That functionality was only ever originally operational because NEXT remembers what methods have already been called and won't call them again. like, it was held together with vibes and memory 🙈

Using this now causes infinite recursion between MyApp::setup and Catalyst::setup, due to other backwards compatibility issues related to how plugin setup works. Moose method modifiers like before|after|around setup => sub { ... }; also will not operate correctly on the setup method.

The right way to do it is this:

after setup_finalize => sub {
    ... # things to do after the actual setup
};

The setup_finalize hook was introduced as a way to avoid this issue. use it, bestie 🫶

⭐ Components with a new method which returns false

Previously, if you had a component which inherited from Catalyst::COMPONENT, but overrode the new method to return false, then your class's configuration would be blessed into a hash on your behalf, and this would be returned from the COMPONENT method.

This behavior makes no sense, and so has been removed. Implementing your own new method in components is highly discouraged. Instead, you should inherit the new method from Catalyst::Component, and use Moose's BUILD functionality and/or Moose attributes to perform any construction work necessary for your class. that's the move 💅

💖 `PACKAGE->mk_accessor('meta');`

Won't work due to a limitation of Moose. This is currently being fixed inside Moose. (we're all just waiting, babe 💀)

🌈 Class::Data::Inheritable side effects

Previously, writing to a class data accessor would copy the accessor method down into your package.

This behavior has been removed. While the class data is still stored per-class, it is stored on the metaclass of the class defining the accessor.

Therefore anything relying on the side effect of the accessor being copied down will be broken.

The following test demonstrates the problem:

{
    package BaseClass;
    use base qw/Class::Data::Inheritable/;
    __PACKAGE__->mk_classdata('foo');
}

{
    package Child;
    use base qw/BaseClass/;
}

BaseClass->foo('base class');
Child->foo('sub class');

use Test::More;
isnt(BaseClass->can('foo'), Child->can('foo'));

🧚 Extending Catalyst::Request or other classes in an ad hoc manner using mk_accessors

Previously, it was possible to add additional accessors to Catalyst::Request (or other classes) by calling the mk_accessors class method.

This is no longer supported — users should make a subclass of the class whose behavior they would like to change, rather than globally polluting the Catalyst objects. no more touching other people's stuff, we're classy now 👑

🔥 Confused multiple inheritance with Catalyst::Component::COMPONENT

Previously, Catalyst's COMPONENT method would delegate to the method on the right hand side, which could then delegate back again with NEXT. This is poor practice, and in addition, makes no sense with C3 method dispatch order — and is therefore no longer supported.

If a COMPONENT method is detected in the inheritance hierarchy to the right hand side of Catalyst::Component::COMPONENT, then the following warning message will be emitted:

There is a COMPONENT method resolving after Catalyst::Component
in ${next_package}.

The correct fix is to re-arrange your class's inheritance hierarchy so that the COMPONENT method you would like to inherit is the first (left-hand most) COMPONENT method in your @ISA. just scoot it over 💫

🍓 Development server relying on environment variables

Previously, the development server would allow propagation of system environment variables into the request environment. This has changed with the adoption of Plack. You can use Plack::Middleware::ForceEnv to achieve the same effect.

🚨 WARNINGS 🚨

okay bestie, sit down, this is the part where Catalyst is like "hey. i love u. but pls stop doing this." 💅 none of these are gonna break ur app today, but they're all on the way out, so like... take the hint, okay?

👀 Actions in your application class

having actions chillin' in your application class? that now throws a warning at application startup, because it's deprecated, periodt. the move is to get those actions out of there and into a MyApp::Controller::Root — exactly like the scaffold app that catalyst.pl generates for u. do that, it's the vibe. ✨

this warning also shows up in ur tests!! 😭 yeah. so u should move actions out of ur test too, and make a myTest::Controller::Root, like this:

package MyTest::Controller::Root;

use strict;
use warnings;

use parent 'Catalyst::Controller';

__PACKAGE__->config(namespace => '');

sub action : Local {
    my ( $self, $c ) = @_;
    $c->do_something;
}

1;

look at that. beautiful. no notes. 🫶

🎀 `::[MVC]::` naming scheme

having packages called MyApp::[MVC]::XX? deprecated, bestie. and catalyst.pl can't generate that for u anymore, it literally won't do it.

it's still supported, to be fair, but the recommendation is u rename ur application components to Model / View / Controller. do it, ur future self will thank u. 💖

and yeah — a warning gets issued at application startup if the ::[MVC]:: naming scheme is in use. so like, everyone will know. 🙈

💀 `Catalyst::Base`

any code using Catalyst::Base will now emit a warning. this module is getting removed in a future release. rip in advance, fr fr.

🌸 Methods in `Catalyst::Dispatcher`

these following methods in Catalyst::Dispatcher are implementation details. they may change in the 5.8X release series, which means using them is highly deprecated. i cannot stress this enough, bestie:

tree
dispatch_types
registered_dispatch_types
method_action_class
action_hash
container_hash

the first time one of these methods gets called, a warning is emitted:

Class $class is calling the deprecated method Catalyst::Dispatcher::$public_method_name,
this will be removed in Catalyst 5.9

u should NEVER be calling any of these methods from application code. like. never ever. i'm serious. 🛑

plugin authors and maintainers whose plugins currently call these methods should switch to using the public API. OR — and this is the important part — if u don't feel the public API adequately supports ur use case, pls email the development list to discuss what API features u need, so u can be appropriately supported. they're not trying to leave u hanging, they just need to know. 💌

🧚 Class files with names that don't correspond to the packages they define

in this version of Catalyst, if a component gets loaded from disk but no symbols are defined in that component's name space after it's loaded, u get this warning:

require $class was successful but the package is not defined.

this exists to protect u from confusing bugs caused by mistyping package names. and heads up: it will become a fatal error in a future version. so like... fix it now while it's just yelling at u instead of killing ur app. 😭

pls note that 'inner packages' (via Devel::InnerPackage) are still fully supported. this warning only fires when the component file naming doesn't map to any of the packages defined within that component. so don't panic if that's what ur doing, ur fine. 🍓

🦋 `$c->plugin` method

calling the plugin method is deprecated. calling it at run time is highly deprecated. double deprecated. no cap.

instead, the recommendation is to use Catalyst::Model::Adaptor or similar, so u can compose the functionality u need outside of the main application name space. much cleaner, much more main character energy. 👑

calling the plugin method will not be supported past Catalyst 5.81. so. that's the deadline, bestie. 💀

and that's a wrap on the whole page!! 🌈 this was Catalyst's upgrade-to-5.9 guide, and it comes to u from the Catalyst contributors, who wrote it and put it out into the world for Perl v5.40.0, dated 2024-11-15. thank u for reading, ily, go fix ur warnings. 💜 ✨ 🎀

📦 where this page comes from

debian trixie: libcatalyst-perl 5.90132-1 · Artistic-1.0-Perl OR GPL-1.0-or-later
ubuntu resolute: libcatalyst-perl 5.90132-1 · Artistic-1.0-Perl OR GPL-1.0-or-later
ubuntu stonking: libcatalyst-perl 5.90132-1 · Artistic-1.0-Perl OR GPL-1.0-or-later
💖 girlified by deepseek-ai/DeepSeek-V4.1-Flash on 2026-10-14: a language model's rewrite of the original, under its terms