Remove instanceof check

.lintstagedrc.json

@@ -1,5 +1,8 @@
 {
-  "*.{js,ts}": ["eslint --max-warnings 0 --fix", "prettier --write"],
+  "*.{js,ts}": [
+    "eslint --max-warnings 0 --fix --no-warn-ignored",
+    "prettier --write"
+  ],
   "*.json": "prettier --write",
   "*.md": "prettier --write"
 }

eslint.config.mjs

@@ -21,8 +21,7 @@ export default tsConfig(
       'npmDist',
       'npmEsmDist',
       'denoDist',
-      'website/.next',
-      'website/out',
+      'website/',
       'integrationTests/ts/*.ts',
     ],
   },

src/jsutils/__tests__/instanceOf-test.ts

@@ -70,10 +70,10 @@ describe('instanceOf', () => {
     const Foo2 = getFoo();
 
     expect(() => instanceOf(new Foo1(), Foo2)).to.throw(
-      /^Cannot use Foo "{}" from another module or realm./m,
+      /Cannot use Foo from another module or realm/m,
     );
     expect(() => instanceOf(new Foo2(), Foo1)).to.throw(
-      /^Cannot use Foo "{}" from another module or realm./m,
+      /Cannot use Foo from another module or realm/m,
     );
   });
 });

src/jsutils/instanceOf.ts

@@ -1,56 +1,28 @@
-import { inspect } from './inspect.js';
-
-/* c8 ignore next 3 */
-const isProduction =
-  globalThis.process != null &&
-  // eslint-disable-next-line no-undef
-  process.env.NODE_ENV === 'production';
-
 /**
  * A replacement for instanceof which includes an error warning when multi-realm
  * constructors are detected.
  * See: https://expressjs.com/en/advanced/best-practice-performance.html#set-node_env-to-production
  * See: https://webpack.js.org/guides/production/
  */
-export const instanceOf: (value: unknown, constructor: Constructor) => boolean =
-  /* c8 ignore next 6 */
-  // FIXME: https://github.com/graphql/graphql-js/issues/2317
-  isProduction
-    ? function instanceOf(value: unknown, constructor: Constructor): boolean {
-        return value instanceof constructor;
-      }
-    : function instanceOf(value: unknown, constructor: Constructor): boolean {
-        if (value instanceof constructor) {
-          return true;
-        }
-        if (typeof value === 'object' && value !== null) {
-          // Prefer Symbol.toStringTag since it is immune to minification.
-          const className = constructor.prototype[Symbol.toStringTag];
-          const valueClassName =
-            // We still need to support constructor's name to detect conflicts with older versions of this library.
-            Symbol.toStringTag in value
-              ? value[Symbol.toStringTag]
-              : value.constructor?.name;
-          if (className === valueClassName) {
-            const stringifiedValue = inspect(value);
-            throw new Error(
-              `Cannot use ${className} "${stringifiedValue}" from another module or realm.
-
-Ensure that there is only one instance of "graphql" in the node_modules
-directory. If different versions of "graphql" are the dependencies of other
-relied on modules, use "resolutions" to ensure only one version is installed.
-
-https://yarnpkg.com/en/docs/selective-version-resolutions
-
-Duplicate "graphql" modules cannot be used at the same time since different
-versions may have different capabilities and behavior. The data from one
-version used in the function from another could produce confusing and
-spurious results.`,
-            );
-          }
-        }
-        return false;
-      };
+export function instanceOf(value: unknown, constructor: Constructor): boolean {
+  if (value instanceof constructor) {
+    return true;
+  }
+  if (typeof value === 'object' && value !== null) {
+    const className = constructor.prototype[Symbol.toStringTag];
+    const valueClassName =
+      // We still need to support constructor's name to detect conflicts with older versions of this library.
+      Symbol.toStringTag in value
+        ? value[Symbol.toStringTag]
+        : value.constructor?.name;
+    if (className === valueClassName) {
+      throw new Error(
+        `Multiple GraphQL instances detected, Cannot use ${className} from another module or realm. Read more at https://graphql-js.org/errors#1`,
+      );
+    }
+  }
+  return false;
+}
 
 interface Constructor {
   prototype: {

website/pages/_meta.ts

@@ -24,6 +24,7 @@ const meta = {
     title: 'FAQ',
   },
   'going-to-production': '',
+  errors: '',
   'api-v16': {
     type: 'menu',
     title: 'API',

website/pages/errors.mdx

@@ -0,0 +1,14 @@
+# Errors
+
+## 1
+
+Ensure that there is only one instance of "graphql" in the node_modules
+directory. If different versions of "graphql" are the dependencies of other
+relied on modules, use "resolutions" to ensure only one version is installed.
+
+https://yarnpkg.com/en/docs/selective-version-resolutions
+
+Duplicate "graphql" modules cannot be used at the same time since different
+versions may have different capabilities and behavior. The data from one
+version used in the function from another could produce confusing and
+spurious results.