fix(http-executor): don't force application/json content type (#5825)

* fix(http-executor): don't force application/json content type

* test(executors): regression test on setting custom introspection header

* chore: added changeset for http-executor fix

* chore: removed nock dependency

* fix: removed unused dependency

* chore: unnecessary JSON stringify

* chore: reset yarn lock

* test: assert on number of assertions

* Apply suggestions from code review

---------

Co-authored-by: Arda TANRIKULU <ardatanrikulu@gmail.com>

Author: felamaslen

.changeset/swift-suits-promise.md

@@ -0,0 +1,5 @@
+---
+'@graphql-tools/executor-http': patch
+---
+
+Fixed http executor to allow custom content-type header

packages/executors/http/src/index.ts

@@ -200,7 +200,7 @@ export function buildHTTPExecutor(
             ),
           )
             .then(body => {
-              if (typeof body === 'string') {
+              if (typeof body === 'string' && !headers['content-type']) {
                 headers['content-type'] = 'application/json';
               }
               const fetchOptions: RequestInit = {

packages/executors/http/tests/buildHTTPExecutor.test.ts

@@ -144,4 +144,37 @@ describe('buildHTTPExecutor', () => {
       }
     `);
   });
+
+  it('should allow setting a custom content-type header in introspection', async () => {
+    expect.assertions(2);
+
+    const executor = buildHTTPExecutor({
+      endpoint: 'https://my.schema/graphql',
+      fetch(_url, options) {
+        expect(options?.headers?.['content-type']).toBe('application/vnd.api+json');
+        return Response.json({ data: { hello: 'world' } });
+      },
+      headers: { 'content-type': 'application/vnd.api+json' },
+    });
+    const result = (await executor({
+      document: parse(/* GraphQL */ `
+        query IntrospectionQuery {
+          __schema {
+            queryType {
+              name
+            }
+            mutationType {
+              name
+            }
+            subscriptionType {
+              name
+            }
+          }
+        }
+      `),
+      context: {},
+    })) as ExecutionResult;
+
+    expect(result.errors).toBeUndefined();
+  });
 });