Fix fetchJSON adds useless Content-Type header for empty requests

packages/ra-core/src/dataProvider/fetch.spec.ts

@@ -62,15 +62,25 @@ describe('flattenObject', () => {
 });
 
 describe('createHeadersFromOptions', () => {
-    it('should add a Content-Type header for POST requests', () => {
-        const options = {
+    it('should add a Content-Type header for POST requests if there is a body', () => {
+        const optionsWithBody = {
             method: 'POST',
+            body: JSON.stringify(null),
         };
 
-        const headers = createHeadersFromOptions(options);
+        const headers = createHeadersFromOptions(optionsWithBody);
         expect(headers.get('Content-Type')).toStrictEqual('application/json');
     });
 
+    it('should not add a Content-Type header for POST requests with no body', () => {
+        const optionsWithoutBody = {
+            method: 'POST',
+        };
+
+        const headersWithoutBody = createHeadersFromOptions(optionsWithoutBody);
+        expect(headersWithoutBody.get('Content-Type')).toBeNull();
+    });
+
     it('should not add a Content-Type header for GET requests', () => {
         const optionsWithoutMethod = {};
         const optionsWithMethod = {
@@ -85,4 +95,41 @@ describe('createHeadersFromOptions', () => {
         );
         expect(headersWithoutMethod.get('Content-Type')).toBeNull();
     });
+
+    it('should not add a Content-Type header for DELETE requests with no body', () => {
+        const optionsWithDelete = {
+            method: 'DELETE',
+        };
+
+        const headersWithDelete = createHeadersFromOptions(optionsWithDelete);
+        expect(headersWithDelete.get('Content-Type')).toBeNull();
+        const optionsWithDeleteAndBody = {
+            method: 'DELETE',
+            body: JSON.stringify(null),
+        };
+
+        const headersWithDeleteAndBody = createHeadersFromOptions(
+            optionsWithDeleteAndBody
+        );
+        expect(headersWithDeleteAndBody.get('Content-Type')).toStrictEqual(
+            'application/json'
+        );
+    });
+
+    it('should not add a Content-Type header if there already is a Content-Type header', () => {
+        const optionsWithContentType = {
+            headers: new Headers({
+                'Content-Type': 'not undefined',
+            }) as Headers,
+            method: 'POST',
+            body: 'not undefined either',
+        };
+
+        const headersWithContentType = createHeadersFromOptions(
+            optionsWithContentType
+        );
+        expect(headersWithContentType.get('Content-Type')).toStrictEqual(
+            'not undefined'
+        );
+    });
 });

packages/ra-core/src/dataProvider/fetch.ts

@@ -13,13 +13,17 @@ export const createHeadersFromOptions = (options: Options): Headers => {
         new Headers({
             Accept: 'application/json',
         })) as Headers;
-    if (
-        !requestHeaders.has('Content-Type') &&
-        !(options && (!options.method || options.method === 'GET')) &&
-        !(options && options.body && options.body instanceof FormData)
-    ) {
+    const hasBody = options && options.body;
+    const isContentTypeSet = requestHeaders.has('Content-Type');
+    const isGetMethod = !options?.method || options?.method === 'GET';
+    const isFormData = options?.body instanceof FormData;
+
+    const shouldSetContentType =
+        hasBody && !isContentTypeSet && !isGetMethod && !isFormData;
+    if (shouldSetContentType) {
         requestHeaders.set('Content-Type', 'application/json');
     }
+
     if (options.user && options.user.authenticated && options.user.token) {
         requestHeaders.set('Authorization', options.user.token);
     }