Add discriminator map default type support

Author: Kirill Nesmeyanov

src/Mapping/DiscriminatorMap.php

@@ -4,6 +4,8 @@
 
 namespace TypeLang\Mapper\Mapping;
 
+use JetBrains\PhpStorm\Language;
+
 /**
  * ```
  * #[DiscriminatorMap(field: 'type', map: [
@@ -24,12 +26,30 @@ class DiscriminatorMap
 {
     public function __construct(
         /**
+         * The property holding the type discriminator
+         *
          * @var non-empty-string
          */
         public readonly string $field,
         /**
+         * The mapping between field value and types, i.e.
+         *
+         * ```
+         * [
+         *     'admin_user' => AdminUser::class,
+         *     'admin_users' => 'list<AdminUser>',
+         * ]
+         *
          * @var non-empty-array<non-empty-string, non-empty-string>
          */
         public readonly array $map,
+        /**
+         * Default type if the discriminator field ({@see $field}) is missing
+         * or does not match the mapping rules ({@see $map})
+         *
+         * @var non-empty-string|null
+         */
+        #[Language('PHP')]
+        public readonly ?string $otherwise = null,
     ) {}
 }

src/Mapping/Driver/AttributeDriver.php

@@ -145,6 +145,7 @@ protected function load(
         $attribute = $this->findClassAttribute($reflection, DiscriminatorMap::class);
         if ($attribute !== null) {
             $mapping = [];
+            $default = null;
 
             foreach ($attribute->map as $mappedValue => $mappedType) {
                 $mapping[$mappedValue] = $this->createDiscriminatorType(
@@ -155,9 +156,19 @@ class: $reflection,
                 );
             }
 
+            if ($attribute->otherwise !== null) {
+                $default = $this->createDiscriminatorType(
+                    type: $attribute->otherwise,
+                    class: $reflection,
+                    types: $types,
+                    parser: $parser,
+                );
+            }
+
             $class->setDiscriminator(new DiscriminatorMapMetadata(
                 field: $attribute->field,
                 map: $mapping,
+                default: $default,
             ));
         }
     }

src/Mapping/Metadata/ClassMetadata.php

@@ -61,8 +61,6 @@ public function __construct(
      *
      * Required to print type information in exceptions.
      *
-     * @api
-     *
      * @codeCoverageIgnore
      */
     public function getTypeStatement(Context $context): TypeStatement

src/Mapping/Metadata/DiscriminatorMapMetadata.php

@@ -22,6 +22,7 @@ public function __construct(
          * @var non-empty-array<non-empty-string, TypeMetadata>
          */
         private readonly array $map,
+        private ?TypeMetadata $default = null,
         ?int $createdAt = null,
     ) {
         parent::__construct($createdAt);
@@ -73,11 +74,30 @@ public function getField(): string
     }
 
     /**
-     * Dynamically creates AST discriminator representation.
+     * Returns default mapping type for transformations that do not comply
+     * with the specified mapping rules defined in {@see getMapping()}.
      *
-     * Required to print type information in exceptions.
+     * @api
+     */
+    public function getDefaultType(): ?TypeMetadata
+    {
+        return $this->default;
+    }
+
+    /**
+     * Updates default mapping type.
      *
      * @api
+     */
+    public function setDefaultType(?TypeMetadata $type): void
+    {
+        $this->default = $type;
+    }
+
+    /**
+     * Dynamically creates AST discriminator representation.
+     *
+     * Required to print type information in exceptions.
      *
      * @codeCoverageIgnore
      */

src/Mapping/NormalizeAsArray.php

@@ -9,10 +9,9 @@ final class NormalizeAsArray
 {
     public function __construct(
         /**
-         * Enables normalization of an object value as an
-         * associative {@see array} if {@see $enabled} is set
-         * to {@see true} or use anonymous {@see object} in case of
-         * parameter is set to {@see false}.
+         * Enables normalization of an object value as an associative
+         * {@see array} if {@see $enabled} is set to {@see true} or use
+         * anonymous {@see object} in case of parameter is set to {@see false}.
          */
         public readonly bool $enabled = true,
     ) {}

src/Type/ClassType/ClassTypeDenormalizer.php

@@ -82,10 +82,19 @@ public function cast(mixed $value, Context $context): mixed
      */
     private function castOverDiscriminator(DiscriminatorMapMetadata $map, array $value, Context $context): mixed
     {
+        // Default mapping type
+        $default = $map->getDefaultType()
+            ?->getType();
+
         $field = $map->getField();
 
         // In case of discriminator field is missing
         if (!\array_key_exists($field, $value)) {
+            // In case of default type is present
+            if ($default !== null) {
+                return $default->cast($value, $context);
+            }
+
             throw MissingRequiredObjectFieldException::createFromContext(
                 field: $field,
                 expected: $map->getTypeStatement(),
@@ -98,6 +107,11 @@ private function castOverDiscriminator(DiscriminatorMapMetadata $map, array $val
 
         // In case of discriminator field is not a string
         if (!\is_string($element)) {
+            // In case of default type is present
+            if ($default !== null) {
+                return $default->cast($value, $context);
+            }
+
             throw InvalidObjectValueException::createFromContext(
                 element: $element,
                 field: $field,
@@ -111,6 +125,11 @@ private function castOverDiscriminator(DiscriminatorMapMetadata $map, array $val
 
         // In case of discriminator value is not found
         if ($mapping === null) {
+            // In case of default type is present
+            if ($default !== null) {
+                return $default->cast($value, $context);
+            }
+
             throw InvalidObjectValueException::createFromContext(
                 element: $element,
                 field: $field,