fix(graphcache): Disregard write-only operation during schema awareness (#3621)

Author: JoviDeCroock

.changeset/lazy-kangaroos-think.md

@@ -0,0 +1,5 @@
+---
+"@urql/exchange-graphcache": patch
+---
+
+Disregard write-only operation when fragment-matching with schema awareness

exchanges/graphcache/src/operations/shared.ts

@@ -236,7 +236,10 @@ export function makeSelectionIterator(
                     ctx.store.logger
                   ));
 
-            if (isMatching || currentOperation === 'write') {
+            if (
+              isMatching ||
+              (currentOperation === 'write' && !ctx.store.schema)
+            ) {
               if (process.env.NODE_ENV !== 'production')
                 pushDebugNode(typename, fragment);
               const isFragmentOptional = isOptional(select);