fix: don't set default request method when creating a Request (#6154)

In the case of creating a Request with the parameters `(Request, object)`,
there was a bug that method and headers are set from the default created by
the init rather then the already present value from the request param.
This is because for a to me unknown reason the order in which the parameters
are processed is reversed.

This fixes that by adding a check which stops the defaults from being set,
unless they are explicitly passed.

Fixes: https://github.com/oven-sh/bun/issues/6144

2 files changed, 24 insertions, 13 deletions

diff --git a/src/bun.js/webcore/request.zig b/src/bun.js/webcore/request.zig
index 381ae2750..7f37bea46 100644
--- a/src/bun.js/webcore/request.zig
+++ b/src/bun.js/webcore/request.zig
@@ -507,10 +507,9 @@ pub const Request = struct {
         };
         const values_to_try = values_to_try_[0 .. @as(usize, @intFromBool(!is_first_argument_a_url)) +
             @as(usize, @intFromBool(arguments.len > 1 and arguments[1].isObject()))];
-
         for (values_to_try) |value| {
             const value_type = value.jsType();
-
+            const explicit_check = values_to_try.len == 2 and value_type == .FinalObject and values_to_try[1].jsType() == .DOMWrapper;
             if (value_type == .DOMWrapper) {
                 if (value.as(Request)) |request| {
                     if (values_to_try.len == 1) {
@@ -625,23 +624,25 @@ pub const Request = struct {
 
             if (!fields.contains(.method) or !fields.contains(.headers)) {
                 if (Body.Init.init(globalThis.allocator(), globalThis, value) catch null) |init| {
-                    if (!fields.contains(.method)) {
-                        req.method = init.method;
-                        fields.insert(.method);
+                    if (!explicit_check or (explicit_check and value.fastGet(globalThis, .method) != null)) {
+                        if (!fields.contains(.method)) {
+                            req.method = init.method;
+                            fields.insert(.method);
+                        }
                     }
-
-                    if (init.headers) |headers| {
-                        if (!fields.contains(.headers)) {
-                            req.headers = headers;
-                            fields.insert(.headers);
-                        } else {
-                            headers.deref();
+                    if (!explicit_check or (explicit_check and value.fastGet(globalThis, .headers) != null)) {
+                        if (init.headers) |headers| {
+                            if (!fields.contains(.headers)) {
+                                req.headers = headers;
+                                fields.insert(.headers);
+                            } else {
+                                headers.deref();
+                            }
                         }
                     }
                 }
             }
         }
-
         if (req.url.isEmpty()) {
             globalThis.throw("Failed to construct 'Request': url is required.", .{});
             req.finalizeWithoutDeinit();
diff --git a/test/js/web/fetch/fetch.test.ts b/test/js/web/fetch/fetch.test.ts
index 85e2296cd..4f7b20d3c 100644
--- a/test/js/web/fetch/fetch.test.ts
+++ b/test/js/web/fetch/fetch.test.ts
@@ -1241,6 +1241,16 @@ describe("Request", () => {
     expect(req.signal.aborted).toBe(true);
   });
 
+  it("copies method (#6144)", () => {
+    const request = new Request("http://localhost:1337/test", {
+      method: "POST",
+    });
+    const new_req = new Request(request, {
+      body: JSON.stringify({ message: "Hello world" }),
+    });
+    expect(new_req.method).toBe("POST");
+  });
+
   it("cloned signal", async () => {
     gc();
     const controller = new AbortController();