use WeakMap to manage sets to reclaim memory as possible

Author: yaacovCR

src/execution/execute.ts

@@ -48,7 +48,7 @@ import { GraphQLStreamDirective } from '../type/directives.js';
 import type { GraphQLSchema } from '../type/schema.js';
 import { assertValidSchema } from '../type/validate.js';
 
-import type { TaggedFieldNode } from './collectFields.js';
+import type { GroupedFieldSet, TaggedFieldNode } from './collectFields.js';
 import {
   collectFields,
   collectSubfields as _collectSubfields,
@@ -123,7 +123,7 @@ export interface ExecutionContext {
   subscribeFieldResolver: GraphQLFieldResolver<any, any>;
   errors: Array<GraphQLError>;
   subsequentPayloads: Set<AsyncPayloadRecord>;
-  branches: Set<string>;
+  branches: WeakMap<GroupedFieldSet, Set<string>>;
 }
 
 /**
@@ -502,7 +502,7 @@ export function buildExecutionContext(
     typeResolver: typeResolver ?? defaultTypeResolver,
     subscribeFieldResolver: subscribeFieldResolver ?? defaultFieldResolver,
     subsequentPayloads: new Set(),
-    branches: new Set(),
+    branches: new WeakMap(),
     errors: [],
   };
 }
@@ -515,18 +515,24 @@ function buildPerEventExecutionContext(
     ...exeContext,
     rootValue: payload,
     subsequentPayloads: new Set(),
-    branches: new Set(),
+    branches: new WeakMap(),
     errors: [],
   };
 }
 
 function shouldBranch(
   exeContext: ExecutionContext,
+  groupedFieldSet: GroupedFieldSet,
   path: Path | undefined,
 ): boolean {
+  const set = exeContext.branches.get(groupedFieldSet);
   const key = pathToArray(path).join('.');
-  if (!exeContext.branches.has(key)) {
-    exeContext.branches.add(key);
+  if (set === undefined) {
+    exeContext.branches.set(groupedFieldSet, new Set([key]));
+    return true;
+  }
+  if (!set.has(key)) {
+    set.add(key);
     return true;
   }
   return false;
@@ -591,7 +597,10 @@ function executeOperation(
       );
   }
 
-  if (newDeferDepth !== undefined && shouldBranch(exeContext, path)) {
+  if (
+    newDeferDepth !== undefined &&
+    shouldBranch(exeContext, groupedFieldSet, path)
+  ) {
     executeDeferredFragment(
       exeContext,
       rootType,
@@ -1587,7 +1596,10 @@ function collectAndExecuteSubfields(
     asyncPayloadRecord,
   );
 
-  if (newDeferDepth !== undefined && shouldBranch(exeContext, path)) {
+  if (
+    newDeferDepth !== undefined &&
+    shouldBranch(exeContext, groupedFieldSet, path)
+  ) {
     executeDeferredFragment(
       exeContext,
       returnType,