Refactor string checks into utils

Author: spawnia

src/Regex.php

@@ -7,7 +7,6 @@
 use GraphQL\Error\Error;
 use GraphQL\Error\InvariantViolation;
 use GraphQL\Language\AST\Node;
-use GraphQL\Language\AST\StringValueNode;
 use GraphQL\Type\Definition\ScalarType;
 use GraphQL\Utils\Utils;
 use Spatie\Regex\Regex as RegexValidator;
@@ -60,13 +59,7 @@ protected function regex(): string
      */
     public function serialize($value): string
     {
-        if (!canBeString($value)) {
-            $safeValue = Utils::printSafe($value);
-
-            throw new InvariantViolation("The given value {$safeValue} can not be serialized.");
-        }
-
-        $stringValue = strval($value);
+        $stringValue = assertString($value, InvariantViolation::class);
 
         if (!$this->matchesRegex($stringValue)) {
             throw new InvariantViolation("The given string $stringValue did not match the regex {$this->regex()}");
@@ -86,14 +79,8 @@ public function serialize($value): string
      */
     public function parseValue($value): string
     {
-        if (!canBeString($value)) {
-            $safeValue = Utils::printSafe($value);
-
-            throw new Error("The given value {$safeValue} can not be serialized.");
-        }
-
-        $stringValue = strval($value);
-
+        $stringValue = assertString($value, Error::class);
+    
         if (!$this->matchesRegex($stringValue)) {
             $safeValue = Utils::printSafeJson($stringValue);
 
@@ -120,12 +107,8 @@ public function parseValue($value): string
      */
     public function parseLiteral($valueNode, array $variables = null): string
     {
-        if (!$valueNode instanceof StringValueNode) {
-            throw new Error("Query error: Can only parse strings got: {$valueNode->kind}", [$valueNode]);
-        }
-
-        $value = $valueNode->value;
-
+        $value = assertStringLiteral($valueNode);
+    
         if (!$this->matchesRegex($value)) {
             $safeValue = Utils::printSafeJson($value);
 

src/utils.php

@@ -4,6 +4,10 @@
 
 namespace MLL\GraphQLScalars;
 
+use GraphQL\Error\Error;
+use GraphQL\Language\AST\StringValueNode;
+use GraphQL\Utils\Utils;
+
 /**
  * Check if a value can be serialized to a string.
  *
@@ -17,3 +21,37 @@ function canBeString($value): bool
         || is_scalar($value)
         || (is_object($value) && method_exists($value, '__toString'));
 }
+
+/**
+ * @param $valueNode
+ *
+ * @return string
+ * @throws Error
+ */
+function assertStringLiteral($valueNode): string
+{
+    if (!$valueNode instanceof StringValueNode) {
+        throw new Error("Query error: Can only parse strings got: {$valueNode->kind}", [$valueNode]);
+    }
+    
+    return $valueNode->value;
+}
+
+/**
+ * Ensure the value is a string and throw an exception if not.
+ *
+ * @param $value
+ * @param string $exceptionClass
+ *
+ * @return string
+ */
+function assertString($value, string $exceptionClass): string
+{
+    if (!canBeString($value)) {
+        $safeValue = Utils::printSafe($value);
+        
+        throw new $exceptionClass("The given value {$safeValue} can not be serialized.");
+    }
+    
+    return strval($value);
+}