Ticket #51757: 51757.patch

src/wp-includes/rest-api.php

@@ -1908 +1908 @@
                 'uniqueItems',
                 'anyOf',
                 'oneOf',
+                'const',
         );
 }
 
@@ -2160 +2161 @@
                 }
         }
 
+        if ( ! empty( $args['const'] ) ) {
+                if ( $value !== $args['const'] ) {
+                        /* translators: 1: Parameter, 2: The valid value. */
+                        return new WP_Error( 'rest_invalid_param', sprintf( __( '%1$s is not const %2$s.' ), $param, $args['const'] ) );
+                }
+        }
+
         if ( in_array( $args['type'], array( 'integer', 'number' ), true ) ) {
                 if ( ! is_numeric( $value ) ) {
                         return new WP_Error(

tests/phpunit/tests/rest-api/rest-schema-validation.php

@@ -62 +62 @@
                 $this->assertWPError( rest_validate_value_from_schema( 1123, $schema ) );
         }
 
+        /**
+         * @ticket 51757
+         */
+        public function test_const() {
+                $schema  = array(
+                        'type'  => 'string',
+                        'const' => 'ananas',
+                );
+                $valid   = 'ananas';
+                $invalid = 'pineapple';
+
+                $this->assertTrue( rest_validate_value_from_schema( $valid, $schema ) );
+                $this->assertWPError( rest_validate_value_from_schema( $invalid, $schema ) );
+
+                // By definition, const is functionally equivalent to an enum with a single value.
+                // However, they produce different error messages, so the invalid isn't tested.
+                $enum_schema = array(
+                        'type'  => 'string',
+                        'enum' => array( 'ananas' ),
+                );
+                $this->assertSame(
+                        rest_validate_value_from_schema( $valid, $schema ),
+                        rest_validate_value_from_schema( $valid, $enum_schema )
+                );
+        }
+
         public function test_format_email() {
                 $schema = array(
                         'type'   => 'string',