Merge branch 'hotfix/239' into develop

Forward port #239

CHANGELOG.md

@@ -33,6 +33,8 @@ Fifth release candidate.
 - [#238](https://github.com/zendframework/zend-expressive/pull/238) adds a
   cookbook recipe detailing how to handle serving an Expressive application from
   a subdirectory of your web root.
+- [#239](https://github.com/zendframework/zend-expressive/pull/239) adds a
+  cookbook recipe detailing how to create modular Expressive applications.
 
 ### Deprecated
 

doc/book/cookbook/bookdown.json

@@ -6,6 +6,7 @@
         {"Setting custom 404 page handling": "custom-404-page-handling.md"},
         {"Registering custom view helpers when using zend-view": "using-custom-view-helpers.md"},
         {"Using zend-form view helpers": "using-zend-form-view-helpers.md"},
-        {"Using Expressive from a subdirectory": "using-a-base-path.md"}
+        {"Using Expressive from a subdirectory": "using-a-base-path.md"},
+        {"Building modular applications": "modular-layout.md"}
     ]
 }

doc/book/cookbook/modular-layout.md

@@ -0,0 +1,157 @@
+# How can I make my application modular?
+
+Zend Framework 2 applications have a concept of modules, independent units that
+can provide configuration, services, and hooks into its MVC lifecycle. This
+functionality is provided by zend-modulemanager.
+
+While zend-modulemanager could be used with Expressive, we suggest another
+approach: modules that are based only on configuration. This powerful approach
+doesn't affect performance, and offers extensive flexibility: each module can
+provide its own services (with factories), default configuration, and routes. 
+
+This cookbook will show how to organize modules using 
+[mtymek/expressive-config-manager](https://github.com/mtymek/expressive-config-manager),
+a lightweight library that aggregates and merges configuration, optionally caching it.
+
+## Install the configuration manager
+
+The configuration manager is available in Packagist:
+
+```bash
+$ composer require mtymek/expressive-config-manager
+```
+
+## Generate your config
+
+The default Expressive skeleton installs a `config/config.php` file, which
+aggregates all configuration. When using the configuration manager, you will
+need to replace the contents of that file with the following code: 
+
+```php
+<?php
+
+use Zend\Expressive\ConfigManager\ConfigManager;
+use Zend\Expressive\ConfigManager\PhpFileProvider;
+
+$configManager = new ConfigManager([
+    new PhpFileProvider('config/autoload/{{,*.}global,{,*.}local}.php'),
+]);
+
+return new ArrayObject($configManager->getMergedConfig());
+```
+
+If you open your application in a browser, it should still work in exactly the
+same way as it was before. Now you can start adding your modules.
+
+## First module
+
+`ConfigManager` does not force you to use any particular structure for your
+module; its only requirement is to expose default configuration using a "config
+provider", which is simply an invokable class that returns a configuration
+array.
+
+For instance, this is how your module could provide its own routes:
+
+```php
+namespace App;
+
+class AppConfig
+{
+    public function __invoke()
+    {
+        return [
+            'routes' => [
+                [
+                    'name' => 'api.list-transactions',
+                    'path' => '/api/transactions',
+                    'middleware' => App\Action\ListTransactionsAction::class,
+                    'allowed_methods' => ['GET'],
+                ],
+                [
+                    'name' => 'api.refund-transaction',
+                    'path' => '/api/refund',
+                    'middleware' => App\Action\RefundAction::class,
+                    'allowed_methods' => ['POST'],
+                ],
+            ],
+        ];
+    }
+}
+```
+
+## Enabling the module
+
+Finally, you can enable your module by adding a reference to your config class
+within the arguments of the `ConfigManager` constructor in the `config/config.php`
+file:
+
+```php
+$configManager = new ConfigManager([
+    App\AppConfig::class,
+    new PhpFileProvider('config/autoload/{{,*.}global,{,*.}local}.php'),
+]);
+```
+
+## Caching configuration
+
+In order to provide configuration caching, two things must occur:
+
+- First, you must define a `config_cache_enabled` key in your configuration
+  somewhere.
+- Second, you must pass a second argument to the `ConfigManager`, the location
+  of the cache file to use.
+
+The `config_cache_enabled` key can be defined in any of your configuration
+providers, including the autoloaded configuration files. We recommend defining
+them in two locations:
+
+- `config/autoload/global.php` should define the value to `true`, as the
+  production setting.
+- `config/autoload/local.php` should also define the setting, and use a value
+  appropriate to the current environment. In development, for instance, this
+  would be `false`.
+
+```php
+// config/autoload/global.php
+
+return [
+    'config_cache_enabled' => true,
+    /* ... */
+];
+
+// config/autoload/local.php
+
+return [
+    'config_cache_enabled' => false, // <- development!
+    /* ... */
+];
+```
+
+You would then alter your `config/config.php` file to add the second argument.
+The following example builds on the previous, and demonstrates having the
+`AppConfig` entry enabled. The configuration will be cached to
+`data/config-cache.php` in the application root:
+
+```php
+$configManager = new ConfigManager([
+    App\AppConfig::class,
+    new PhpFileProvider('config/autoload/{{,*.}global,{,*.}local}.php'),
+], 'data/config-cache.php');
+```
+
+When the configuration cache path is present, if the `config_cache_enabled` flag
+is enabled, then configuration will be read from the cached configuration,
+instead of parsing and merging the various configuration sources.
+
+## Final notes
+
+This approach may look simple, but it is flexible and powerful:
+
+- You pass a list of config providers to the `ConfigManager` constructor.
+- Configuration is merged in the same order as it is passed, with later entries
+  having precedence.
+- You can override module configuration using `*.global.php` and `*.local.php` files.
+- If cached config is found, `ConfigManager` does not iterate over provider list.
+
+For more details, please refer to the
+[Config Manager Documentation](https://github.com/mtymek/expressive-config-manager#expressive-configuration-manager).

mkdocs.yml

@@ -13,7 +13,7 @@ pages:
     - { Helpers: [{ Introduction: helpers/intro.md }, { UrlHelper: helpers/url-helper.md }, { ServerUrlHelper: helpers/server-url-helper.md }] }
     - { Emitters: emitters.md }
     - { Examples: usage-examples.md }
-    - { Cookbook: [{ 'Prepending a common path to all routes': cookbook/common-prefix-for-routes.md }, { 'Route-specific middleware pipelines': cookbook/route-specific-pipeline.md }, { 'Setting custom 404 page handling': cookbook/custom-404-page-handling.md }, { 'Registering custom view helpers when using zend-view': cookbook/using-custom-view-helpers.md }, { 'Using zend-form view helpers': cookbook/using-zend-form-view-helpers.md }, { 'Using Expressive from a subdirectory': cookbook/using-a-base-path.md }] }
+    - { Cookbook: [{ 'Prepending a common path to all routes': cookbook/common-prefix-for-routes.md }, { 'Route-specific middleware pipelines': cookbook/route-specific-pipeline.md }, { 'Setting custom 404 page handling': cookbook/custom-404-page-handling.md }, { 'Registering custom view helpers when using zend-view': cookbook/using-custom-view-helpers.md }, { 'Using zend-form view helpers': cookbook/using-zend-form-view-helpers.md }, { 'Using Expressive from a subdirectory': cookbook/using-a-base-path.md }, { 'Building modular applications': cookbook/modular-layout.md }] }
     - { 'Expressive Projects': expressive-projects.md }
 site_name: zend-expressive
 site_description: 'zend-expressive: PSR-7 Middleware Microframework'