@@ -187,7 +187,7 @@ type Middleware = (request: Request, response: Response) => Promise<void>;
187187 * configure behavior, and returns an express middleware.
188188 */
189189export function graphqlHTTP ( options :Options ) :Middleware {
190- devAssert ( options != null , 'GraphQL middleware requires options.' ) ;
190+ devAssertIsNonNullable ( options , 'GraphQL middleware requires options.' ) ;
191191
192192return async function graphqlMiddleware (
193193request :Request ,
@@ -239,9 +239,8 @@ export function graphqlHTTP(options: Options): Middleware {
239239optionsData . formatError ??
240240formatErrorFn ;
241241
242- // Assert that schema is required.
243- devAssert (
244- schema != null ,
242+ devAssertIsObject (
243+ schema ,
245244'GraphQL middleware options must contain a schema.' ,
246245) ;
247246
@@ -432,8 +431,8 @@ export function graphqlHTTP(options: Options): Middleware {
432431 :options ,
433432) ;
434433
435- devAssert (
436- optionsResult != null && typeof optionsResult === 'object' ,
434+ devAssertIsObject (
435+ optionsResult ,
437436'GraphQL middleware option function must return an options object or a promise which will be resolved to an options object.' ,
438437) ;
439438
@@ -533,9 +532,17 @@ function sendResponse(response: Response, type: string, data: string): void {
533532response . end ( chunk ) ;
534533}
535534
536- function devAssert ( condition :unknown , message :string ) : assertscondition {
535+ function devAssertIsObject ( value :unknown , message :string ) :void {
536+ devAssert ( value != null && typeof value === 'object' , message ) ;
537+ }
538+
539+ function devAssertIsNonNullable ( value :unknown , message :string ) :void {
540+ devAssert ( value != null , message ) ;
541+ }
542+
543+ function devAssert ( condition :unknown , message :string ) :void {
537544const booleanCondition = Boolean ( condition ) ;
538545if ( ! booleanCondition ) {
539- throw new Error ( message ) ;
546+ throw new TypeError ( message ) ;
540547}
541548}