fix(Bun.serve) fix buffering edge case (#5152)

* fix buffering clean

* fix resolveMaybeNeedsTrailingSlash and try to fix ci/cd error

* fix resolveMaybeNeedsTrailingSlash and try to fix ci/cd error

* oops

---------

Co-authored-by: Jarred Sumner <jarred@jarredsumner.com>

4 files changed, 35 insertions, 3 deletions

diff --git a/src/bun.js/api/server.zig b/src/bun.js/api/server.zig
index 390f8ef96..ac0f04f34 100644
--- a/src/bun.js/api/server.zig
+++ b/src/bun.js/api/server.zig
@@ -2723,7 +2723,7 @@ fn NewRequestContext(comptime ssl_enabled: bool, comptime debug_mode: bool, comp
         }
 
         pub fn doRender(this: *RequestContext) void {
-            ctxLog("render", .{});
+            ctxLog("doRender", .{});
 
             if (this.flags.aborted) {
                 this.finalizeForAbort();
@@ -3039,7 +3039,7 @@ fn NewRequestContext(comptime ssl_enabled: bool, comptime debug_mode: bool, comp
 
                 if (last) {
                     var bytes = this.request_body_buf;
-                    defer this.request_body_buf = .{};
+
                     var old = body.value;
 
                     const total = bytes.items.len + chunk.len;
@@ -3070,6 +3070,7 @@ fn NewRequestContext(comptime ssl_enabled: bool, comptime debug_mode: bool, comp
                         };
                         // }
                     }
+                    this.request_body_buf = .{};
 
                     if (old == .Locked) {
                         var vm = this.server.vm;
diff --git a/src/bun.js/javascript.zig b/src/bun.js/javascript.zig
index 60364706e..6ce145d82 100644
--- a/src/bun.js/javascript.zig
+++ b/src/bun.js/javascript.zig
@@ -1716,7 +1716,7 @@ pub const VirtualMachine = struct {
                     printed,
                 ),
             };
-            res.* = ErrorableString.err(error.NameTooLong, ResolveMessage.create(global, VirtualMachine.get().allocator, msg, source.utf8()).asVoid());
+            res.* = ErrorableString.err(error.NameTooLong, ResolveMessage.create(global, VirtualMachine.get().allocator, msg, source_utf8.slice()).asVoid());
             return;
         }
 
diff --git a/test/js/bun/http/big-form-data.fixture.js b/test/js/bun/http/big-form-data.fixture.js
new file mode 100644
index 000000000..72036a222
--- /dev/null
+++ b/test/js/bun/http/big-form-data.fixture.js
@@ -0,0 +1,20 @@
+const content = "Bun".repeat(15360000);
+
+const server = Bun.serve({
+  port: 0,
+  fetch: async req => {
+    const data = await req.formData();
+    return new Response(data.get("name") === content ? "OK" : "NO");
+  },
+});
+
+const formData = new FormData();
+formData.append("name", content);
+const result = await fetch(`http://${server.hostname}:${server.port}`, {
+  method: "POST",
+  body: formData,
+}).then(res => res.text());
+
+server.stop();
+
+process.exit(result === "OK" ? 0 : 1);
diff --git a/test/js/bun/http/bun-server.test.ts b/test/js/bun/http/bun-server.test.ts
index 3e0e4e71e..398ef4bb7 100644
--- a/test/js/bun/http/bun-server.test.ts
+++ b/test/js/bun/http/bun-server.test.ts
@@ -1,4 +1,5 @@
 import { describe, expect, test } from "bun:test";
+import { bunExe, bunEnv } from "harness";
 
 describe("Server", () => {
   test("normlizes incoming request URLs", async () => {
@@ -357,4 +358,14 @@ describe("Server", () => {
       server.stop(true);
     }
   });
+
+  test("should not crash with big formData", async () => {
+    const proc = Bun.spawn({
+      cmd: [bunExe(), "big-form-data.fixture.js"],
+      cwd: import.meta.dir,
+      env: bunEnv,
+    });
+    await proc.exited;
+    expect(proc.exitCode).toBe(0);
+  });
 });