version assertion

.c8rc.json

@@ -3,6 +3,7 @@
   "include": ["src/"],
   "exclude": [
     "src/**/index.ts",
+    "src/noMultipleVersions.ts",
     "src/**/*-fuzz.ts",
     "src/jsutils/Maybe.ts",
     "src/jsutils/ObjMap.ts",

resources/build-npm.ts

@@ -47,7 +47,15 @@ assert(
 const tsHost = ts.createCompilerHost(tsOptions);
 tsHost.writeFile = (filepath, body) => {
   fs.mkdirSync(path.dirname(filepath), { recursive: true });
-  writeGeneratedFile(filepath, body);
+  let bodyToWrite = body;
+  const filePath = filepath.split('npmDist')[1];
+  if (filePath.endsWith('.js') && !filepath.endsWith('noMultipleVersions.js')) {
+    bodyToWrite =
+      `import '${
+        new Array(filePath.split('/').length - 2).fill('..').join('/') || '.'
+      }/noMultipleVersions.js';\n` + bodyToWrite;
+  }
+  writeGeneratedFile(filepath, bodyToWrite);
 };
 
 const tsProgram = ts.createProgram(['src/index.ts'], tsOptions, tsHost);
@@ -109,6 +117,7 @@ function buildPackageJSON() {
   // Temporary workaround to allow "internal" imports, no grantees provided
   packageJSON.exports['./*.js'] = './*.js';
   packageJSON.exports['./*'] = './*.js';
+  packageJSON.exports['./noMultipleVersions.js'] = null;
 
   // TODO: move to integration tests
   const publishTag = packageJSON.publishConfig?.tag;

resources/utils.ts

@@ -115,7 +115,7 @@ interface PackageJSON {
   repository?: { url?: string };
   scripts?: { [name: string]: string };
   type?: string;
-  exports: { [path: string]: string };
+  exports: { [path: string]: string | null };
   types?: string;
   typesVersions: { [ranges: string]: { [path: string]: Array<string> } };
   devDependencies?: { [name: string]: string };

src/error/GraphQLError.ts

@@ -29,13 +29,22 @@ export interface GraphQLErrorOptions {
   extensions?: Maybe<GraphQLErrorExtensions>;
 }
 
+const isGraphQLErrorSymbol = Symbol.for('GraphQLError');
+
+export function isGraphQLError(error: unknown): error is GraphQLError {
+  return (
+    typeof error === 'object' && error != null && isGraphQLErrorSymbol in error
+  );
+}
+
 /**
  * A GraphQLError describes an Error found during the parse, validate, or
  * execute phases of performing a GraphQL operation. In addition to a message
  * and stack trace, it also includes information about the locations in a
  * GraphQL document and/or execution result that correspond to the Error.
  */
 export class GraphQLError extends Error {
+  [isGraphQLErrorSymbol]: true = true;
   /**
    * An array of `{ line, column }` locations within the source GraphQL document
    * which correspond to this error.

src/execution/subscribe.ts

@@ -3,7 +3,7 @@ import { isAsyncIterable } from '../jsutils/isAsyncIterable';
 import type { Maybe } from '../jsutils/Maybe';
 import { addPath, pathToArray } from '../jsutils/Path';
 
-import { GraphQLError } from '../error/GraphQLError';
+import { GraphQLError, isGraphQLError } from '../error/GraphQLError';
 import { locatedError } from '../error/locatedError';
 
 import type { DocumentNode } from '../language/ast';
@@ -169,7 +169,7 @@ export async function createSourceEventStream(
   } catch (error) {
     // If it GraphQLError, report it as an ExecutionResult, containing only errors and no data.
     // Otherwise treat the error as a system-class error and re-throw it.
-    if (error instanceof GraphQLError) {
+    if (isGraphQLError(error)) {
       return { errors: [error] };
     }
     throw error;

src/index.ts

@@ -26,6 +26,9 @@
  * @packageDocumentation
  */
 
+// eslint-disable-next-line import/no-unassigned-import
+import './noMultipleVersions';
+
 // The GraphQL.js version info.
 export { version, versionInfo } from './version';
 

src/language/source.ts

@@ -1,12 +1,13 @@
 import { devAssert } from '../jsutils/devAssert';
 import { inspect } from '../jsutils/inspect';
-import { instanceOf } from '../jsutils/instanceOf';
 
 interface Location {
   line: number;
   column: number;
 }
 
+const isSourceSymbol = Symbol.for('Source');
+
 /**
  * A representation of source input to GraphQL. The `name` and `locationOffset` parameters are
  * optional, but they are useful for clients who store GraphQL documents in source files.
@@ -15,6 +16,7 @@ interface Location {
  * The `line` and `column` properties in `locationOffset` are 1-indexed.
  */
 export class Source {
+  [isSourceSymbol]: true = true;
   body: string;
   name: string;
   locationOffset: Location;
@@ -53,5 +55,7 @@ export class Source {
  * @internal
  */
 export function isSource(source: unknown): source is Source {
-  return instanceOf(source, Source);
+  return (
+    typeof source === 'object' && source != null && isSourceSymbol in source
+  );
 }

src/noMultipleVersions.ts

@@ -0,0 +1,21 @@
+import { version } from './version';
+
+const graphqlVersionSymbol = Symbol.for('loadedGraphQLVersion');
+
+const currentVersion = (
+  globalThis as { [graphqlVersionSymbol]?: undefined | string }
+)[graphqlVersionSymbol];
+
+if (currentVersion) {
+  if (currentVersion !== version) {
+    // eslint-disable-next-line no-console
+    console.warn(
+      `Loading GraphQL.js version ${version} while ${currentVersion} has already been loaded.\n` +
+        'Please consider configuring your package manager or bundler to only install and resolve a single version of GraphQL.',
+    );
+  }
+} else {
+  (globalThis as { [graphqlVersionSymbol]?: undefined | string })[
+    graphqlVersionSymbol
+  ] = version;
+}