predicates: use brand check in production

Author: yaacovCR

src/jsutils/__tests__/instanceOf-test.ts

@@ -11,9 +11,12 @@ describe('instanceOf', () => {
       }
     }
 
-    expect(instanceOf(true, Foo)).to.equal(false);
-    expect(instanceOf(null, Foo)).to.equal(false);
-    expect(instanceOf(Object.create(null), Foo)).to.equal(false);
+    expect(instanceOf(true, true, Foo)).to.equal(false);
+    expect(instanceOf(false, true, Foo)).to.equal(false);
+    expect(instanceOf(true, null, Foo)).to.equal(false);
+    expect(instanceOf(false, null, Foo)).to.equal(false);
+    expect(instanceOf(true, Object.create(null), Foo)).to.equal(false);
+    expect(instanceOf(false, Object.create(null), Foo)).to.equal(false);
   });
 
   it('detect name clashes with older versions of this lib', () => {
@@ -33,8 +36,10 @@ describe('instanceOf', () => {
 
     const NewClass = newVersion();
     const OldClass = oldVersion();
-    expect(instanceOf(new NewClass(), NewClass)).to.equal(true);
-    expect(() => instanceOf(new OldClass(), NewClass)).to.throw();
+    expect(instanceOf(true, new NewClass(), NewClass)).to.equal(true);
+    expect(instanceOf(false, new NewClass(), NewClass)).to.equal(false);
+    expect(() => instanceOf(true, new OldClass(), NewClass)).to.throw();
+    expect(instanceOf(false, new OldClass(), NewClass)).to.equal(false);
   });
 
   it('allows instances to have share the same constructor name', () => {
@@ -49,12 +54,16 @@ describe('instanceOf', () => {
 
     const Foo = getMinifiedClass('Foo');
     const Bar = getMinifiedClass('Bar');
-    expect(instanceOf(new Foo(), Bar)).to.equal(false);
-    expect(instanceOf(new Bar(), Foo)).to.equal(false);
+    expect(instanceOf(true, new Foo(), Bar)).to.equal(false);
+    expect(instanceOf(false, new Foo(), Bar)).to.equal(false);
+    expect(instanceOf(true, new Bar(), Foo)).to.equal(false);
+    expect(instanceOf(false, new Bar(), Foo)).to.equal(false);
 
     const DuplicateOfFoo = getMinifiedClass('Foo');
-    expect(() => instanceOf(new DuplicateOfFoo(), Foo)).to.throw();
-    expect(() => instanceOf(new Foo(), DuplicateOfFoo)).to.throw();
+    expect(() => instanceOf(true, new DuplicateOfFoo(), Foo)).to.throw();
+    expect(instanceOf(false, new DuplicateOfFoo(), Foo)).to.equal(false);
+    expect(() => instanceOf(true, new Foo(), DuplicateOfFoo)).to.throw();
+    expect(instanceOf(false, new Foo(), DuplicateOfFoo)).to.equal(false);
   });
 
   it('fails with descriptive error message', () => {
@@ -69,11 +78,13 @@ describe('instanceOf', () => {
     const Foo1 = getFoo();
     const Foo2 = getFoo();
 
-    expect(() => instanceOf(new Foo1(), Foo2)).to.throw(
+    expect(() => instanceOf(true, new Foo1(), Foo2)).to.throw(
       /^Cannot use Foo "{}" from another module or realm./m,
     );
-    expect(() => instanceOf(new Foo2(), Foo1)).to.throw(
+    expect(instanceOf(false, new Foo1(), Foo2)).to.equal(false);
+    expect(() => instanceOf(true, new Foo2(), Foo1)).to.throw(
       /^Cannot use Foo "{}" from another module or realm./m,
     );
+    expect(instanceOf(false, new Foo2(), Foo1)).to.equal(false);
   });
 });

src/jsutils/instanceOf.ts

@@ -1,4 +1,5 @@
 import { inspect } from './inspect.js';
+import { invariant } from './invariant.js';
 
 /* c8 ignore next 3 */
 const isProduction =
@@ -7,34 +8,42 @@ const isProduction =
   process.env.NODE_ENV === 'production';
 
 /**
- * A replacement for instanceof which includes an error warning when multi-realm
- * constructors are detected.
+ * A utility which throws an error warning when multi-realm constructors are detected,
+ * triggered by a positive brand check and a negative instanceof (for an object).
+ *
+ * When not in development mode, only the brand check is used.
+ *
  * 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 */
+export const instanceOf: (
+  brandCheck: true | undefined,
+  value: unknown,
+  constructor: Constructor,
+) => boolean =
+  /* c8 ignore next 9 */
   // FIXME: https://github.com/graphql/graphql-js/issues/2317
   isProduction
-    ? function instanceOf(value: unknown, constructor: Constructor): boolean {
-        return value instanceof constructor;
+    ? function instanceOf(brandCheck: true | undefined): boolean {
+        return brandCheck === true;
       }
-    : function instanceOf(value: unknown, constructor: Constructor): boolean {
+    : function instanceOf(
+        brandCheck: true | undefined,
+        value: unknown,
+        constructor: Constructor,
+      ): boolean {
+        if (!brandCheck) {
+          return false;
+        }
         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.
+        invariant(typeof value === 'object' && value !== null);
+        // Prefer Symbol.toStringTag since it is immune to minification.
+        const className = constructor.prototype[Symbol.toStringTag];
+        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
@@ -46,10 +55,7 @@ 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;
+        );
       };
 
 interface Constructor {

src/language/source.ts

@@ -14,6 +14,8 @@ interface Location {
  * The `line` and `column` properties in `locationOffset` are 1-indexed.
  */
 export class Source {
+  readonly __isSource = true as const;
+
   body: string;
   name: string;
   locationOffset: Location;
@@ -47,5 +49,5 @@ export class Source {
  * @internal
  */
 export function isSource(source: unknown): source is Source {
-  return instanceOf(source, Source);
+  return instanceOf((source as any)?.__isSource, source, Source);
 }