Switch to using 'devAssert' similar to graphql-js

.eslintrc.yml

@@ -490,8 +490,7 @@ overrides:
  '@typescript-eslint/no-throw-literal': error
  '@typescript-eslint/no-type-alias': off # TODO consider
  '@typescript-eslint/no-unnecessary-boolean-literal-compare': error
- # FIXME: Disabled to enable checking conditions that would be prevented by types anyway
- '@typescript-eslint/no-unnecessary-condition': off
+ '@typescript-eslint/no-unnecessary-condition': off # TODO blocked by https://github.com/typescript-eslint/typescript-eslint/issues/2752
  '@typescript-eslint/no-unnecessary-qualifier': error
  '@typescript-eslint/no-unnecessary-type-arguments': error
  '@typescript-eslint/no-unnecessary-type-assertion': error

src/index.ts

@@ -187,9 +187,7 @@ type Middleware = (request: Request, response: Response) => Promise<void>;
  * configure behavior, and returns an express middleware.
  */
 export function graphqlHTTP(options: Options): Middleware {
- if (options == null) {
- throw new Error('GraphQL middleware requires options.');
- }
+ devAssert(options != null, 'GraphQL middleware requires options.');
 
  return async function graphqlMiddleware(
  request: Request,
@@ -242,12 +240,10 @@ export function graphqlHTTP(options: Options): Middleware {
  formatErrorFn;
 
  // Assert that schema is required.
- if (schema == null) {
- throw httpError(
- 500,
- 'GraphQL middleware options must contain a schema.',
- );
- }
+ devAssert(
+ schema != null,
+ 'GraphQL middleware options must contain a schema.',
+ );
 
  // GraphQL HTTP only supports GET and POST methods.
  if (request.method !== 'GET' && request.method !== 'POST') {
@@ -436,12 +432,10 @@ export function graphqlHTTP(options: Options): Middleware {
  : options,
  );
 
- // Assert that optionsData is in fact an Object.
- if (optionsResult == null || typeof optionsResult !== 'object') {
- throw new Error(
- 'GraphQL middleware option function must return an options object or a promise which will be resolved to an options object.',
- );
- }
+ devAssert(
+ optionsResult != null && typeof optionsResult === 'object',
+ 'GraphQL middleware option function must return an options object or a promise which will be resolved to an options object.',
+ );
 
  if (optionsResult.formatError) {
  // eslint-disable-next-line no-console
@@ -538,3 +532,10 @@ function sendResponse(response: Response, type: string, data: string): void {
  response.setHeader('Content-Length', String(chunk.length));
  response.end(chunk);
 }
+
+function devAssert(condition: unknown, message: string): asserts condition {
+ const booleanCondition = Boolean(condition);
+ if (!booleanCondition) {
+ throw new Error(message);
+ }
+}