Default to draft-04 if $schema is undefined

Previous behavior was to throw a RuntimeException.

Author: erayd

src/JsonSchema/Constraints/SchemaConstraint.php

@@ -23,6 +23,8 @@
  */
 class SchemaConstraint extends Constraint
 {
+    const DEFAULT_SCHEMA_SPEC = 'http://json-schema.org/draft-04/schema#';
+
     /**
      * {@inheritdoc}
      */
@@ -42,13 +44,16 @@ public function check(&$element, $schema = null, JsonPointer $path = null, $i =
             throw new InvalidArgumentException('no schema found to verify against');
         }
 
-        // validate schema against whatever is defined in $validationSchema->$schema
+        // validate schema against whatever is defined in $validationSchema->$schema. If no
+        // schema is defined, assume self::DEFAULT_SCHEMA_SPEC (currently draft-04).
         if ($this->factory->getConfig(self::CHECK_MODE_VALIDATE_SCHEMA)) {
             if (!$this->getTypeCheck()->isObject($validationSchema)) {
                 throw new RuntimeException('cannot validate non-object schema');
             }
-            if (!$this->getTypeCheck()->propertyExists($validationSchema, '$schema')) {
-                throw new RuntimeException('$schema is not set');
+            if ($this->getTypeCheck()->propertyExists($validationSchema, '$schema')) {
+                $schemaSpec = $this->getTypeCheck()->propertyGet($validationSchema, '$schema');
+            } else {
+                $schemaSpec = self::DEFAULT_SCHEMA_SPEC;
             }
 
             // preload standard schema specs
@@ -58,7 +63,6 @@ public function check(&$element, $schema = null, JsonPointer $path = null, $i =
                 'http://json-schema.org/draft-04/schema' => 'json-schema-draft-04.json',
                 'http://json-schema.org/draft-04/schema#' => 'json-schema-draft-04.json'
             );
-            $schemaSpec = $this->getTypeCheck()->propertyGet($validationSchema, '$schema');
             $schemaStorage = $this->factory->getSchemaStorage();
             foreach ($preload as $schemaID => $schemaFile) {
                 $schemaStorage->addSchema(

tests/Constraints/SchemaValidationTest.php

@@ -49,6 +49,18 @@ public function getValidTests()
                     }
                 }',
                 ''
+            ),
+            array( // inline schema with default (undefined) spec
+                '{
+                    "$schema": {
+                        "properties": {
+                            "propertyOne": {
+                                "type": "string"
+                            }
+                        }
+                    }
+                }',
+                ''
             )
         );
     }
@@ -64,10 +76,4 @@ public function testNonObjectSchema()
         $this->setExpectedException('JsonSchema\Exception\RuntimeException');
         parent::testValidCases('{"$schema": "notAnObject"}', '');
     }
-
-    public function testMissingSchemaSpec()
-    {
-        $this->setExpectedException('JsonSchema\Exception\RuntimeException');
-        parent::testValidCases('{"$schema":{}}', '');
-    }
 }