Validate static schema on middleware mount

src/__tests__/http-test.ts

@@ -248,6 +248,35 @@ function runTests(server: Server) {
       });
     });
 
+    it('Reports validation errors for dynamic schema', async () => {
+      const app = server();
+
+      app.get(
+        urlString(),
+        graphqlHTTP(() => Promise.resolve({ schema: TestSchema })),
+      );
+
+      const response = await app.request().get(
+        urlString({
+          query: '{ test, unknownOne, unknownTwo }',
+        }),
+      );
+
+      expect(response.status).to.equal(400);
+      expect(JSON.parse(response.text)).to.deep.equal({
+        errors: [
+          {
+            message: 'Cannot query field "unknownOne" on type "QueryRoot".',
+            locations: [{ line: 1, column: 9 }],
+          },
+          {
+            message: 'Cannot query field "unknownTwo" on type "QueryRoot".',
+            locations: [{ line: 1, column: 21 }],
+          },
+        ],
+      });
+    });
+
     it('Errors when missing operation name', async () => {
       const app = server();
 

src/__tests__/usage-test.ts

@@ -117,4 +117,19 @@ describe('Useful errors when incorrectly used', () => {
       ],
     });
   });
+
+  it('requires a valid schema if static schema is defined in options', () => {
+    const options = () => ({
+      // @ts-expect-error
+      schema: new GraphQLSchema({ directives: [null] }),
+    });
+    const { schema } = options();
+    expect(() => {
+      graphqlHTTP({ schema });
+    }).to.throw('GraphQL schema validation failed');
+
+    expect(() => {
+      graphqlHTTP(options);
+    }).not.to.throw();
+  });
 });

src/index.ts

@@ -190,6 +190,12 @@ export function graphqlHTTP(options: Options): Middleware {
     throw new Error('GraphQL middleware requires options.');
   }
 
+  const staticSchemaValidationErrors =
+    'schema' in options ? validateSchema(options.schema) : undefined;
+
+  if (staticSchemaValidationErrors?.length) {
+    throw Error('GraphQL schema validation failed');
+  }
   return async function graphqlMiddleware(
     request: Request,
     response: Response,
@@ -272,7 +278,8 @@ export function graphqlHTTP(options: Options): Middleware {
       }
 
       // Validate Schema
-      const schemaValidationErrors = validateSchema(schema);
+      const schemaValidationErrors =
+        staticSchemaValidationErrors ?? validateSchema(schema);
       if (schemaValidationErrors.length > 0) {
         // Return 500: Internal Server Error if invalid schema.
         throw httpError(500, 'GraphQL schema validation error.', {