fetch: reject an unreadable Bun.file() request body with a TypeError

src/runtime/webcore/fetch.rs

@@ -55,7 +55,7 @@ use bun_core::{String as BunString, Tag as BunStringTag, ZigStringSlice};
 use bun_http::{self as http, FetchRedirect, Headers, HeadersExt as _, MimeType};
 use bun_http_jsc::method_jsc;
 use bun_http_types::Method::Method;
-use bun_jsc::{HTTPHeaderName, StringJsc as _, SysErrorJsc as _};
+use bun_jsc::{HTTPHeaderName, StringJsc as _};
 use bun_paths::{self, PathBuffer};
 use bun_sys::FdExt as _;
 // `FromJsEnum for FetchRedirect` lives in bun_http_jsc; importing the impl crate
@@ -368,6 +368,11 @@ fn reject_on_exception(
     Ok(JSPromise::dangerously_create_rejected_promise_value_without_notifying_vm(global_this, err))
 }
 
+/// Same `TypeError` shape as the network errors from `FetchTasklet::on_reject`.
+fn request_body_file_error(err: &bun_sys::Error, global_this: &JSGlobalObject) -> JSValue {
+    jsc::SystemError::from(err.to_system_error()).to_type_error_instance(global_this)
+}
+
 // ──────────────────────────────────────────────────────────────────────────
 // URLType
 // ──────────────────────────────────────────────────────────────────────────
@@ -1709,7 +1714,7 @@ fn fetch_impl<const ALLOW_GET_BODY: bool>(
 
             let opened_fd = match opened_fd_res {
                 Err(err) => {
-                    let err_js = err.to_js(global_this);
+                    let err_js = request_body_file_error(&err, global_this);
                     let rejected_value =
                         JSPromise::dangerously_create_rejected_promise_value_without_notifying_vm(
                             global_this,
@@ -1808,7 +1813,7 @@ fn fetch_impl<const ALLOW_GET_BODY: bool>(
                     let rejected_value =
                         JSPromise::dangerously_create_rejected_promise_value_without_notifying_vm(
                             global_this,
-                            err.to_js(global_this),
+                            request_body_file_error(&err, global_this),
                         );
                     body.detach();
                     return Ok(rejected_value);

test/js/bun/http/fetch-file-upload.test.ts

@@ -239,3 +239,68 @@ test("missing file throws the expected error", async () => {
   });
   Bun.gc(true);
 });
+
+// Like the network errors fetch() rejects with, a Bun.file() body that cannot
+// be read rejects with a TypeError that still carries the system error fields.
+describe.concurrent("Bun.file() body that cannot be read rejects with a TypeError", () => {
+  // The body is read before anything is connected, so the promise comes back
+  // already rejected. Checking that (and the system error fields) pins the
+  // rejection to the body, not to the connection the URL would refuse.
+  function earlyRejection(promise: Promise<Response>): Promise<unknown> {
+    const error = promise.then(
+      () => {
+        throw new Error("fetch() resolved");
+      },
+      err => err,
+    );
+    expect(Bun.peek.status(promise)).toBe("rejected");
+    return error;
+  }
+
+  test("file that does not exist (open fails)", async () => {
+    using dir = tempDir("fetch-unreadable-body", {});
+    const path = join(String(dir), "missing.txt");
+
+    const err = await earlyRejection(fetch("http://127.0.0.1:1/", { method: "POST", body: Bun.file(path) }));
+    expect(err).toBeInstanceOf(TypeError);
+    expect(err).toMatchObject({
+      code: "ENOENT",
+      errno: expect.any(Number),
+      syscall: "open",
+      path: expect.stringContaining("missing.txt"),
+    });
+  });
+
+  test("file that does not exist, as the body of a Request", async () => {
+    using dir = tempDir("fetch-unreadable-body", {});
+    const path = join(String(dir), "missing.txt");
+
+    const request = new Request("http://127.0.0.1:1/", { method: "POST", body: Bun.file(path) });
+    const err = await earlyRejection(fetch(request));
+    expect(err).toBeInstanceOf(TypeError);
+    expect(err).toMatchObject({
+      code: "ENOENT",
+      errno: expect.any(Number),
+      syscall: "open",
+      path: expect.stringContaining("missing.txt"),
+    });
+  });
+
+  test("directory (open succeeds, read fails)", async () => {
+    using dir = tempDir("fetch-unreadable-body", {});
+
+    const err = await earlyRejection(fetch("http://127.0.0.1:1/", { method: "POST", body: Bun.file(String(dir)) }));
+    expect(err).toBeInstanceOf(TypeError);
+    expect(err).toMatchObject({ code: "EISDIR", errno: expect.any(Number), syscall: "read" });
+  });
+
+  test("file descriptor that is not open (dup fails)", async () => {
+    const fd = 1 << 30;
+
+    const err = await earlyRejection(fetch("http://127.0.0.1:1/", { method: "POST", body: Bun.file(fd) }));
+    expect(err).toBeInstanceOf(TypeError);
+    expect(err).toMatchObject({ code: expect.any(String), errno: expect.any(Number) });
+    // Windows does not report EBADF for a descriptor number that was never opened.
+    if (!isWindows) expect(err).toMatchObject({ code: "EBADF", fd });
+  });
+});