OverlappingFieldsCanBeMergedRule: Fix performance degradation (#3967)

fixes from #3958 into

benchmark/repeated-fields-benchmark.js

@@ -0,0 +1,15 @@
+'use strict';
+
+const { graphqlSync } = require('graphql/graphql.js');
+const { buildSchema } = require('graphql/utilities/buildASTSchema.js');
+
+const schema = buildSchema('type Query { hello: String! }');
+const source = `{ ${'hello '.repeat(250)}}`;
+
+module.exports = {
+  name: 'Many repeated fields',
+  count: 5,
+  measure() {
+    graphqlSync({ schema, source });
+  },
+};

src/validation/rules/OverlappingFieldsCanBeMergedRule.ts

@@ -5,10 +5,11 @@ import type { ObjMap } from '../../jsutils/ObjMap';
 import { GraphQLError } from '../../error/GraphQLError';
 
 import type {
+  DirectiveNode,
   FieldNode,
   FragmentDefinitionNode,
-  ObjectValueNode,
   SelectionSetNode,
+  ValueNode,
 } from '../../language/ast';
 import { Kind } from '../../language/kinds';
 import { print } from '../../language/printer';
@@ -588,7 +589,7 @@ function findConflict(
     }
 
     // Two field calls must have the same arguments.
-    if (stringifyArguments(node1) !== stringifyArguments(node2)) {
+    if (!sameArguments(node1, node2)) {
       return [
         [responseName, 'they have differing arguments'],
         [node1],
@@ -634,19 +635,41 @@ function findConflict(
   }
 }
 
-function stringifyArguments(fieldNode: FieldNode): string {
-  // FIXME https://github.com/graphql/graphql-js/issues/2203
-  const args = /* c8 ignore next */ fieldNode.arguments ?? [];
-
-  const inputObjectWithArgs: ObjectValueNode = {
-    kind: Kind.OBJECT,
-    fields: args.map((argNode) => ({
-      kind: Kind.OBJECT_FIELD,
-      name: argNode.name,
-      value: argNode.value,
-    })),
-  };
-  return print(sortValueNode(inputObjectWithArgs));
+function sameArguments(
+  node1: FieldNode | DirectiveNode,
+  node2: FieldNode | DirectiveNode,
+): boolean {
+  const args1 = node1.arguments;
+  const args2 = node2.arguments;
+
+  if (args1 === undefined || args1.length === 0) {
+    return args2 === undefined || args2.length === 0;
+  }
+  if (args2 === undefined || args2.length === 0) {
+    return false;
+  }
+
+  /* c8 ignore next */
+  if (args1.length !== args2.length) {
+    /* c8 ignore next */
+    return false;
+    /* c8 ignore next */
+  }
+
+  const values2 = new Map(args2.map(({ name, value }) => [name.value, value]));
+  return args1.every((arg1) => {
+    const value1 = arg1.value;
+    const value2 = values2.get(arg1.name.value);
+    if (value2 === undefined) {
+      return false;
+    }
+
+    return stringifyValue(value1) === stringifyValue(value2);
+  });
+}
+
+function stringifyValue(value: ValueNode): string | null {
+  return print(sortValueNode(value));
 }
 
 // Two types conflict if both types could not apply to a value simultaneously.