Update GraphQlReader.php

Based on feedback from #31879 (comment) @Bartlomiejsz

> regarding first issue - with empty enum. It looks like the fix is to replace first matching group in both $typeDefinitionPattern variables:
>
> ([^\{]*)
> with:
> 
> ([^\{\}]*)
> Then this regex will check if there is neither beginning or ending bracket in this place

Author: convenient

lib/internal/Magento/Framework/GraphQlSchemaStitching/GraphQlReader.php

@@ -242,7 +242,7 @@ private function parseTypes(string $graphQlSchemaContent) : array
     {
         $typeKindsPattern = '(type|interface|union|enum|input)';
         $typeNamePattern = '([_A-Za-z][_0-9A-Za-z]+)';
-        $typeDefinitionPattern = '([^\{]*)(\{[^\}]*\})';
+        $typeDefinitionPattern = '([^\{\}]*)(\{[^\}]*\})';
         $spacePattern = '[\s\t\n\r]+';
 
         preg_match_all(
@@ -357,24 +357,19 @@ private function addPlaceHolderInSchema(string $graphQlSchemaContent) :string
         $typeDefinitionPattern = '([^\{]*)(\{[\s\t\n\r^\}]*\})';
         $spacePattern = '([\s\t\n\r]+)';
 
-        // TODO review this workaround
-        // Replace enums before types, there is a bug in which some enums are caught by the type regex
-        // If we process them first they will have their placeholder inserted appropriately without the :String suffix
-        // This means they will not be caught by the following preg_replace
-        //add placeholder in empty enums
-        $graphQlSchemaContent = preg_replace(
-            "/{$enumKindsPattern}{$spacePattern}{$typeNamePattern}{$spacePattern}{$typeDefinitionPattern}/im",
-            "\$1\$2\$3\$4\$5{\n{$placeholderField}\n}",
-            $graphQlSchemaContent
-        );
-
         //add placeholder in empty types
         $graphQlSchemaContent = preg_replace(
             "/{$typesKindsPattern}{$spacePattern}{$typeNamePattern}{$spacePattern}{$typeDefinitionPattern}/im",
             "\$1\$2\$3\$4\$5{\n{$placeholderField}: String\n}",
             $graphQlSchemaContent
         );
 
+        //add placeholder in empty enums
+        $graphQlSchemaContent = preg_replace(
+            "/{$enumKindsPattern}{$spacePattern}{$typeNamePattern}{$spacePattern}{$typeDefinitionPattern}/im",
+            "\$1\$2\$3\$4\$5{\n{$placeholderField}\n}",
+            $graphQlSchemaContent
+        );
         return $graphQlSchemaContent;
     }