Documenting debug:twig command

Author: yceruto

templating/debug.rst

@@ -67,3 +67,17 @@ By design, the ``dump()`` function is only available in the ``dev`` and ``test``
 environments, to avoid leaking sensitive information in production. In fact,
 trying to use the ``dump()`` function in the ``prod`` environment will result in
 a PHP error.
+
+Execute this command to list all Twig functions, filters, globals, tests and
+registered namespaces and their paths:
+
+.. code-block:: terminal
+
+    # list general information
+    $ php bin/console debug:twig
+
+    # filter output by any keyword
+    $ php bin/console debug:twig --filter=date
+
+    # pass a template name to show the physical file which will be loaded
+    $ php bin/console debug:twig @Twig/Exception/error.html.twig

templating/namespaced_paths.rst

@@ -71,6 +71,13 @@ in the ``vendor/acme/foo-bar/templates/`` directory, you can refer to it as:
 
     {{ include('@foo_bar/sidebar.twig') }}
 
+Execute this command to verify if your template name is correct and know which
+template file will be loaded:
+
+.. code-block:: terminal
+
+    $ php bin/console debug:twig @foo_bar/sidebar.twig
+
 Multiple Paths per Namespace
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 

templating/twig_extension.rst

@@ -70,6 +70,12 @@ Next, register your class as a service and tag it with ``twig.extension``. If yo
 using the :ref:`default services.yaml configuration <service-container-services-load-example>`,
 you're done! Symfony will automatically know about your new service and add the tag.
 
+Execute this command to verify if your new filter was successfully registered:
+
+.. code-block:: terminal
+
+    $ php bin/console debug:twig --filter=price
+
 You can now start using your filter in any Twig template.
 
 Creating Lazy-Loaded Twig Extensions