[Validator] [Validation] Document the auto_mapping config option

Author: javiereguiluz

doctrine.rst

@@ -420,8 +420,12 @@ is smart enough to know if it should INSERT or UPDATE your entity.
 Validating Objects
 ------------------
 
-:doc:`The Symfony validator </validation>` reuses Doctrine metadata to perform
-some basic validation tasks::
+:doc:`The Symfony validator </validation>` can reuse Doctrine metadata to perform
+some basic validation tasks. First, add or configure the
+:ref:`auto_mapping option <reference-validation-auto-mapping>` to define which
+entities should be introspected by Symfony to add automatic validation constraints.
+
+Consider the following controller code::
 
     // src/Controller/ProductController.php
     namespace App\Controller;
@@ -455,9 +459,11 @@ some basic validation tasks::
     }
 
 Although the ``Product`` entity doesn't define any explicit
-:doc:`validation configuration </validation>`, Symfony introspects the Doctrine
-mapping configuration to infer some validation rules. For example, given that
-the ``name`` property can't be ``null`` in the database, a
+:doc:`validation configuration </validation>`, if the ``auto_mapping`` option
+includes it in the list of entities to introspect, Symfony will infer some
+validation rules for it and will apply them.
+
+For example, given that the ``name`` property can't be ``null`` in the database, a
 :doc:`NotNull constraint </reference/constraints/NotNull>` is added automatically
 to the property (if it doesn't contain that constraint already).
 

reference/configuration/framework.rst

@@ -2499,6 +2499,65 @@ enabled
 validation
 ~~~~~~~~~~
 
+.. _reference-validation-auto-mapping:
+
+auto_mapping
+............
+
+**type**: ``array`` **default**: ``[]``
+
+Defines the Doctrine entities that will be introspected to add
+:ref:`automatic validation constraints <automatic_object_validation>` to them:
+
+.. configuration-block::
+
+    .. code-block:: yaml
+
+        framework:
+            validation:
+                auto_mapping:
+                    # an empty array means that all entities that belong to that
+                    # namespace will add automatic validation
+                    'App\Entity\': []
+                    'Foo\': ['Foo\Some\Entity', 'Foo\Another\Entity']
+
+    .. code-block:: xml
+
+        <!-- config/packages/framework.xml -->
+        <?xml version="1.0" encoding="UTF-8" ?>
+        <container xmlns="http://symfony.com/schema/dic/services"
+            xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+            xmlns:framework="http://symfony.com/schema/dic/symfony"
+            xsi:schemaLocation="http://symfony.com/schema/dic/services
+                https://symfony.com/schema/dic/services/services-1.0.xsd
+                http://symfony.com/schema/dic/symfony https://symfony.com/schema/dic/symfony/symfony-1.0.xsd">
+
+            <framework:config>
+                <framework:validation>
+                    <framework:auto-mapping>
+                        <framework:service namespace="App\Entity\"/>
+
+                        <framework:service namespace="Foo\">Foo\Some\Entity</framework:service>
+                        <framework:service namespace="Foo\">Foo\Another\Entity</framework:service>
+                    </framework:auto-mapping>
+                </framework:validation>
+            </framework:config>
+        </container>
+
+    .. code-block:: php
+
+        // config/packages/framework.php
+        use Symfony\Config\FrameworkConfig;
+
+        return static function (FrameworkConfig $framework): void {
+            $framework->validation()
+                ->autoMapping()
+                    ->paths([
+                        'App\\Entity\\' => [],
+                        'Foo\\' => ['Foo\\Some\\Entity', 'Foo\\Another\\Entity'],
+                    ]);
+        };
+
 .. _reference-validation-enabled:
 
 enabled