feat: preserve form data objects in request body

Author: mnorlin

src/openapi-typescript/fetch-factory.ts

@@ -62,12 +62,13 @@ function buildInit(
   options: AllFetchOptions,
   headers: HeadersInit
 ): RequestInit {
+  const serializableObject =
+    options.body &&
+    typeof options.body == "object" &&
+    !((options.body as any) instanceof FormData);
   return {
     ...Object.assign({}, { ...defaultInit }, { ...options }),
-    body:
-      options.body && typeof options.body == "object"
-        ? JSON.stringify(options.body)
-        : options.body,
+    body: serializableObject ? JSON.stringify(options.body) : options.body,
     method: options.method?.toUpperCase(),
     headers,
   };

src/openapi-typescript/types/fetch-options.ts

@@ -23,7 +23,7 @@ export type FetchOptions<Operation> = Omit<
  */
 export type AllFetchOptions<Operation = never> = Omit<RequestInit, "body"> & {
   parameters: FetchParameters<Operation>;
-  body: OperationRequestBody<Operation> | string;
+  body: OperationRequestBody<Operation> | string | FormData;
 };
 
 /**

test/openapi-typescript/fetch-factory.test.ts

@@ -265,7 +265,7 @@ describe("Generated fetch request", () => {
     expect((mockedFetch.mock.calls[0] as any)[1].integrity).toBe("dummy");
   });
 
-  it("stringifies request body", () => {
+  it("stringifies plain JSON request body", () => {
     const body = {
       id: 1,
       petId: 2,
@@ -286,6 +286,19 @@ describe("Generated fetch request", () => {
       JSON.stringify(body)
     );
   });
+
+  it("preserves request body of FormData objects", () => {
+    const body = new FormData();
+
+    customFetch("/store/order", {
+      method: "post",
+      headers: { Accept: "nothing" },
+      integrity: "dummy",
+      body: body,
+    });
+
+    expect((mockedFetch.mock.calls[0] as any)[1].body).toBe(body);
+  });
 });
 
 describe("Generated fetch response", () => {