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1 | =head1 NAME |
2 | |
3 | Catalyst::Upgrading - Instructions for upgrading to the latest Catalyst |
4 | |
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5 | =head1 Upgrading to Catalyst 5.80 |
6 | |
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7 | Most applications and plugins should run unaltered on Catalyst 5.80. |
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8 | |
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9 | However as a lot of refactoring work has taken place, and several changes have |
10 | been made which could cause incompatibilities. If your application or plugin |
11 | is using deprecated code, or relying on side-effects, then you could have |
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12 | issues upgrading to this release. |
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13 | |
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14 | Most issues found with pre-existing components have been easy to solve, and a |
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15 | complete description of behaviour changes which may cause compatibility issues, |
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16 | or warnings which are now emitted is included below to help if you have problems. |
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17 | |
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18 | If you think you have found an upgrade related issue which is not covered in |
19 | this document, then please email the Catalyst list to discuss the problem. |
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20 | |
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21 | =head1 Known backwards compatibility breakages. |
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22 | |
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23 | =head2 Issues with Class::C3 |
24 | |
25 | Catalyst 5.80 uses L<Algorithm::C3> method dispatch order. This is built into |
26 | perl 5.10, and comes via L<Class::C3> for perl 5.8. This replaces L<NEXT> |
27 | with L<Class::C3::Adopt::NEXT>, forcing all components to resolve methods using |
28 | C3, rather than the unpredictable dispatch order of L<NEXT>. |
29 | |
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30 | This issue is characterised by your application failing to start due to an |
31 | error message about having a non-linear @ISA. |
32 | |
33 | The Catalyst plugin most often causing this, is |
34 | L<Catalyst::Plugin::Session::Store::FastMmap> - if you are using this plugin |
35 | and see issues, then please upgrade - and please try upgrading your plugins |
36 | if you have this issue, as it has been fixed. Note that Makefile.PL in the |
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37 | distribution will warn about known incompatible components. |
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38 | |
39 | This issue can, however, be found in your own application - the only solution is |
40 | to go through each base class of the class the error was reported against, until |
41 | you identify the ones in conflict, and resolve them. |
42 | |
43 | To be able to generate a linear @ISA, the list of superclasses for each |
44 | class must be resolvable using the C3 algorithm. Unfortunately, when |
45 | superclasses are being used as mixins (to add functionality used in your class), |
46 | and with multiple inheritence, it is easy to get this wrong. |
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47 | |
48 | Most common is the case of: |
49 | |
50 | package Component1; # Note, this is the common case |
51 | use base qw/Class::Accessor::Fast Class::Data::Inheritable/; |
52 | |
53 | package Component2; # Accidentally saying it this way round causes fail. |
54 | use base qw/Class::Data::Inheritable Class::Accessor::Fast/; |
55 | |
56 | package GoesBang; |
57 | use base qw/Component1 Component2/; |
58 | |
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59 | Any situation like this will cause your application to fail to start. |
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60 | |
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61 | Please see additional documentation about this issue, and how to resolve it in |
62 | L<Class::C3::Adopt::NEXT>. |
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63 | |
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64 | =head2 Components which inherit from Moose::Object before Catalyst::Component |
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65 | |
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66 | Moose components which say: |
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67 | |
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68 | package TestApp::Controller::Example; |
69 | use Moose; |
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70 | extends qw/Moose::Object Catalyst::Component/; |
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71 | |
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72 | to use the constructor provided by Moose, whilst working (if you do some hacks |
73 | with the C< BUILDARGS > method), will not work with Catalyst 5.80 as |
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74 | C<Catalyst::Component> inherits from C<Moose::Object>, and so C< @ISA > fails |
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75 | to linearize. |
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76 | |
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77 | The fix for this is to not inherit directly from C<Moose::Object> |
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78 | yourself. Having components which do not inherit their constructor from |
79 | C<Catalyst::Component> is B<unsupported>, and has never been recommended, |
80 | therefore you're on your own if you're using this technique. You'll need |
81 | to detect the version of Catalyst your application is running with and deal |
82 | with it appropriately. |
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83 | |
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84 | You will also see this issue if you do the following: |
85 | |
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86 | package TestApp::Controller::Example; |
87 | use Moose; |
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88 | use base 'Catalyst::Controller'; |
89 | |
90 | as C< use base > appends to @ISA. |
91 | |
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92 | The correct way to use Moose in a component in a both forward and backwards |
93 | compatible way is: |
94 | |
95 | package TestApp::Controller::Root; |
96 | use Moose; |
97 | BEGIN { extends 'Catalyst::Component' }; # Or ::Controller, or whatever |
98 | |
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99 | Note that the C< extends > declaration needs to occur in a begin block for |
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100 | L<attributes> to operate correctly. |
101 | |
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102 | You also don't get the L<Moose::Object> constructor, and therefore attribute |
103 | initialization will not work as normally expected. If you want to use Moose |
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104 | attributes, then they need to be made lazy to correctly initialize. |
105 | |
106 | Note that this only applies if your component needs to maintain component |
107 | backwards compatibility for Catalyst versions before 5.71001 - in 5.71001 |
108 | attributes work as expected, and the BUILD method is called normally |
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109 | (although BUILDARGS is not). |
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110 | |
111 | If you depend on Catalyst 5.8, then B<all> Moose features work as expected. |
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112 | |
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113 | =head3 use Moose in MyApp |
114 | |
115 | Similar to the above, this will also fail: |
116 | |
117 | package MyApp; |
118 | use Moose; |
119 | use Catalyst qw/ |
120 | ConfigLoader |
121 | /; |
122 | __PACKAGE__->setup; |
123 | |
124 | If you need to use Moose in your application class (e.g. for method modifiers |
125 | etc) then the correct technique is: |
126 | |
127 | package MyApp; |
128 | use Moose; |
129 | extends 'Catalyst'; |
130 | __PACKAGE__->setup(qw/ |
131 | ConfigLoader |
132 | /); |
133 | |
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134 | =head2 Anonymous closures installed directly into the symbol table |
135 | |
136 | If you have any code which installs anonymous subroutine references directly |
137 | into the symbol table, you may encounter breakages. The simplest solution is |
138 | to use L<Sub::Name> to name the subroutine. Example: |
139 | |
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140 | # Original code, likely to break: |
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141 | my $full_method_name = join('::', $package_name, $method_name); |
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142 | *$full_method_name = sub { ... }; |
143 | |
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144 | # Fixed Code |
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145 | use Sub::Name 'subname'; |
146 | my $full_method_name = join('::',$package_name, $method_name); |
147 | *$full_method_name = subname $full_method_name, sub { ... }; |
148 | |
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149 | Additionally, you can take advantage of Catalysts use of L<Class::MOP> and |
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150 | install the closure using the appropriate meta class. Example: |
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151 | |
152 | use Class::MOP; |
153 | my $metaclass = Moose::Meta::Class->initialize($package_name); |
154 | $metaclass->add_method($method_name => sub { ... }); |
155 | |
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156 | =head2 Hooking into application setup |
157 | |
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158 | To execute code during application start-up the following snippet in MyApp.pm |
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159 | used to work: |
160 | |
161 | sub setup { |
162 | my ($class, @args) = @_; |
163 | $class->NEXT::setup(@args); |
164 | ... # things to do after the actual setup |
165 | } |
166 | |
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167 | With Catalyst 5.80 this won't work anymore. Due to the fact that Catalyst is |
168 | no longer using NEXT.pm for method resolution, this no longer works. The |
169 | functionality was only ever originally operational as L<NEXT> remembers what |
170 | methods have already been called, and will not call them again. |
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171 | |
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172 | Using this now causes infinite recursion between MyApp::setup and |
173 | Catalyst::setup, due to other backwards compatibility issues related to how |
174 | plugin setup works. Moose method modifiers like C<< before|after|around 'setup |
175 | => sub { ... }; >> also will not operate correctly on the setup method. |
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176 | |
177 | The right way to do it is this: |
178 | |
179 | after setup_finalize => sub { |
180 | ... # things to do after the actual setup |
181 | }; |
182 | |
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183 | The setup_finalize hook was introduced as a way to avoid this issue. |
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184 | |
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185 | =head2 Components with a new method which returns false |
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186 | |
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187 | Previously, if you had a component which inherited from Catalyst::COMPONENT, |
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188 | but overrode the new method to return false, then your class' configuration |
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189 | would be blessed into a hash on your behalf, and this would be returned from |
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190 | the COMPONENT method. |
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191 | |
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192 | This behaviour makes no sense, and so has been removed. Implementing your own |
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193 | C< new > method in components is B<highly> discouraged, instead, you should |
194 | inherit the new method from Catalyst::Component, and use Mooses BUILD |
195 | functionality and/or Moose attributes to perform any construction work |
196 | necessary for your class. |
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197 | |
198 | =head2 __PACKAGE__->mk_accessor('meta'); |
199 | |
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200 | Won't work due to a limitation of L<Moose>. This is currently being fixed |
201 | inside Moose. |
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202 | |
203 | =head2 Class::Data::Inheritable side effects |
204 | |
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205 | Previously, writing to a class data accessor would copy the accessor method |
206 | down into your package. |
207 | |
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208 | This behaviour has been removed. Whilst the class data is still stored |
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209 | per-class, it is stored on the metaclass of the class defining the accessor. |
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210 | |
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211 | Therefore anything relying on the side-effect of the accessor being copied down |
212 | will be broken. |
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213 | |
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214 | The following test demonstrates the problem: |
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215 | |
216 | { |
217 | package BaseClass; |
218 | use base qw/Class::Data::Inheritable/; |
219 | __PACKAGE__->mk_classdata('foo'); |
220 | } |
221 | |
222 | { |
223 | package Child; |
224 | use base qw/BaseClass/; |
225 | } |
226 | |
227 | BaseClass->foo('base class'); |
228 | Child->foo('sub class'); |
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229 | |
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230 | use Test::More; |
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231 | isnt(BaseClass->can('foo'), Child->can('foo')); |
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232 | |
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233 | =head2 Extending Catalyst::Request or other classes in an ad-hoc manor using mk_accessors |
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234 | |
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235 | Previously, it was possible to add additional accessors to Catalyst::Request |
236 | (or other classes) by calling the mk_accessors class method. |
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237 | |
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238 | This is no longer supported - users should make a sub-class of the class whose |
239 | behaviour they would like to change, rather than globally polluting the |
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240 | Catalyst objects. |
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241 | |
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242 | =head2 Confused multiple inheritance with Catalyst::Component::COMPONENT |
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243 | |
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244 | Previously, Catalyst's COMPONENT method would delegate to the method on the |
245 | right hand side, which could then delegate back again with NEXT. This (as it |
246 | is insane AND makes no sense with C3 method dispatch order), and is therefore |
247 | no longer supported. |
248 | |
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249 | If a COMPONENT method is detected in the inheritance hierarchy to the right |
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250 | hand side of Catalyst::Component::COMPONENT, then the following warning |
251 | message will be emitted: |
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252 | |
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253 | There is a COMPONENT method resolving after Catalyst::Component |
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254 | in ${next_package}. |
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255 | |
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256 | The correct fix is to re-arrange your class' inheritance hierarchy so that the |
257 | COMPONENT method you would like to inherit is the first (left-hand most) |
258 | COMPONENT method in your @ISA. |
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259 | |
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260 | =head1 WARNINGS |
261 | |
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262 | =head2 Catalyst::Base |
263 | |
264 | Any code using L<Catalyst::Base> will now warn, and this module will be removed |
265 | in a future release. |
266 | |
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267 | =head2 Methods in Catalyst::Dispatcher |
268 | |
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269 | The following methods in Catalyst::Dispatcher are both an implementation |
270 | detail, which may change in the 5.8X release series, and therefore their use |
271 | is highly deprecated. |
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272 | |
273 | =over |
274 | |
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275 | =item tree |
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276 | |
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277 | =item dispatch_types |
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278 | |
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279 | =item registered_dispatch_types |
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280 | |
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281 | =item method_action_class |
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282 | |
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283 | =item action_hash |
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284 | |
285 | =item container_hash |
286 | |
287 | =back |
288 | |
289 | The first time one of these methods is called, a warning will be emitted: |
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290 | |
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291 | Class $class is calling the deprecated method Catalyst::Dispatcher::$public_method_name, |
292 | this will be removed in Catalyst 5.9X |
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293 | |
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294 | You should B<NEVER> be calling any of these methods from application code. |
295 | |
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296 | Plugins authors and maintainers whose plugins currently call these methods |
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297 | should change to using the public API, or, if you do not feel the public API |
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298 | adequately supports your use-case, please email the development list to |
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299 | discuss what API features you need so that you can be appropriately supported. |
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300 | |
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301 | =head2 Class files with names that don't correspond to the packages they define |
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302 | |
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303 | In this version of Catalyst, if a component is loaded from disk, but no |
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304 | symbols are defined in that component's name space after it is loaded, this |
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305 | warning will be issued: |
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306 | |
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307 | require $class was successful but the package is not defined. |
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308 | |
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309 | This is to protect against confusing bugs caused by mis-typing package names, |
310 | and will become a fatal error in a future version. |
311 | |
312 | Please note that 'inner packages' (via L<Devel::InnerPackage>) are still fully |
313 | supported, this warning is only issued when component file naming does not map |
314 | to B<any> of the packages defined within that component. |
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315 | |
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316 | =head2 $c->plugin method |
317 | |
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318 | Calling the plugin method is deprecated, and calling it at run time is B<highly |
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319 | deprecated>. |
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320 | |
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321 | Instead you are recommended to use L< Catalyst::Model::Adaptor > or similar to |
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322 | compose the functionality you need outside of the main application name space. |
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323 | |
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324 | Calling the plugin method will not be supported past Catalyst 5.81. |
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325 | |
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326 | =cut |
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327 | |