fix: bypass Content-Type validation when request has no body

src/tests/with-contact.test.ts

@@ -549,9 +549,17 @@ describe('withContract', () => {
 
             expect(response.status).toBe(400);
             expect(response.body.error).toBe(
-                'Unsupported content-type. Allowed: application/x-www-form-urlencoded',
+                'Unsupported content-type. Allowed: application/x-www-form-urlencoded, got: application/json',
             );
         });
+
+        it('should bypass content-type check if request has no body', async () => {
+            const response = await request(app).post('/custom-content-type'); // No .send() and no Content-Type header
+
+            expect(response.status).toBe(400);
+            // The error should be from Zod validation, not the Content-Type check
+            expect(response.body.error).toBe('Invalid request data');
+        });
     });
 
     describe('Schema-less Responses', () => {

src/validator/with-contract.ts

@@ -167,16 +167,23 @@ export function withContract<
 
             // Check content type if body validation is required
             if (config.request?.body) {
-                const contentType = expressReq.headers['content-type'];
-                const allowedContentTypes = config.request?.contentType ?? ['application/json'];
-
-                if (
-                    !contentType ||
-                    !allowedContentTypes.some((type) => contentType.includes(type))
-                ) {
-                    throw new ValidationError(
-                        `Unsupported content-type. Allowed: ${allowedContentTypes.join(', ')}`,
-                    );
+                const hasBody =
+                    expressReq.headers['transfer-encoding'] !== undefined ||
+                    (expressReq.headers['content-length'] !== undefined &&
+                        expressReq.headers['content-length'] !== '0');
+
+                if (hasBody) {
+                    const contentType = expressReq.headers['content-type'];
+                    const allowedContentTypes = config.request?.contentType ?? ['application/json'];
+
+                    if (
+                        !contentType ||
+                        !allowedContentTypes.some((type) => contentType.includes(type))
+                    ) {
+                        throw new ValidationError(
+                            `Unsupported content-type. Allowed: ${allowedContentTypes.join(', ')}, got: ${contentType}`,
+                        );
+                    }
                 }
             }