fix: unhandled error thrown by busboy (#711)

* fix: unhandled error thrown by busboy

As per, https://fetch.spec.whatwg.org/#dom-body-formdata, TypeErrors are
expected to be thrown. Busboy errors were being unhandled.

* chore: apply suggestions from mrbbot's code review

Co-authored-by: MrBBot <me@mrbbot.dev>

* fix: test for formData unsupported Content-Type header

The expectations weren't included in the `throwAsync()`.

---------

Co-authored-by: Bruno Nascimento <bruno.nascimento@csghq.com>
Co-authored-by: MrBBot <me@mrbbot.dev>

packages/core/src/standards/http.ts

@@ -311,40 +311,44 @@ export class Body<Inner extends BaseRequest | BaseResponse> {
       );
     }
     const formData = new FormData();
-    await new Promise<void>(async (resolve) => {
-      const Busboy: typeof import("busboy") = require("busboy");
-      const busboy = Busboy({
-        headers: headers as http.IncomingHttpHeaders,
-        preservePath: true,
-      });
-      busboy.on("field", (name, value) => {
-        formData.append(name, value);
-      });
-      busboy.on("file", (name, value, info) => {
-        const { filename, encoding, mimeType } = info;
-        const base64 = encoding.toLowerCase() === "base64";
-        const chunks: Buffer[] = [];
-        let totalLength = 0;
-        value.on("data", (chunk: Buffer) => {
-          if (base64) chunk = Buffer.from(chunk.toString(), "base64");
-          chunks.push(chunk);
-          totalLength += chunk.byteLength;
+    await new Promise<void>(async (resolve, reject) => {
+      try {
+        const Busboy: typeof import("busboy") = require("busboy");
+        const busboy = Busboy({
+          headers: headers as http.IncomingHttpHeaders,
+          preservePath: true,
         });
-        value.on("end", () => {
-          if (this[kFormDataFiles]) {
-            const file = new File(chunks, filename, { type: mimeType });
-            formData.append(name, file);
-          } else {
-            const text = Buffer.concat(chunks, totalLength).toString();
-            formData.append(name, text);
-          }
+        busboy.on("field", (name, value) => {
+          formData.append(name, value);
         });
-      });
-      busboy.on("finish", resolve);
+        busboy.on("file", (name, value, info) => {
+          const { filename, encoding, mimeType } = info;
+          const base64 = encoding.toLowerCase() === "base64";
+          const chunks: Buffer[] = [];
+          let totalLength = 0;
+          value.on("data", (chunk: Buffer) => {
+            if (base64) chunk = Buffer.from(chunk.toString(), "base64");
+            chunks.push(chunk);
+            totalLength += chunk.byteLength;
+          });
+          value.on("end", () => {
+            if (this[kFormDataFiles]) {
+              const file = new File(chunks, filename, { type: mimeType });
+              formData.append(name, file);
+            } else {
+              const text = Buffer.concat(chunks, totalLength).toString();
+              formData.append(name, text);
+            }
+          });
+        });
+        busboy.on("finish", resolve);
 
-      const body = this[_kInner].body;
-      if (body !== null) for await (const chunk of body) busboy.write(chunk);
-      busboy.end();
+        const body = this[_kInner].body;
+        if (body !== null) for await (const chunk of body) busboy.write(chunk);
+        busboy.end();
+      } catch (e) {
+        reject(new TypeError(e instanceof Error ? e.message : String(e)));
+      }
     });
     if (this[kInputGated]) await waitForOpenInputGate();
     return formData;

packages/core/test/standards/http.spec.ts

@@ -382,7 +382,30 @@ test("Body: formData: respects Content-Transfer-Encoding header for base64 encod
   const formData = await body.formData();
   t.is(formData.get("key"), "test");
 });
-
+test("Body: formData: throw error on missing boundary in Content-Type header", async (t) => {
+  // Check with multipart/form-data Content-Type
+  const body = new Body(
+    new BaseResponse(["second value2", "--boundary--"].join("\r\n"), {
+      headers: { "content-type": "multipart/form-data" },
+    })
+  );
+  await t.throwsAsync(body.formData(), {
+    instanceOf: TypeError,
+    message: "Multipart: Boundary not found",
+  });
+});
+test("Body: formData: throw error on unsupported Content-Type header", async (t) => {
+  // Check with application/json Content-Type
+  const body = new Body(
+    new BaseResponse(["second value2", "--boundary--"].join("\r\n"), {
+      headers: { "content-type": "application/json" },
+    })
+  );
+  await t.throwsAsync(body.formData(), {
+    instanceOf: TypeError,
+    message: "Unsupported content type: application/json",
+  });
+});
 test("Request: constructing from BaseRequest doesn't create new BaseRequest unless required", (t) => {
   // Check properties of Request are same as BaseRequest if not RequestInit passed
   const controller = new AbortController();