[autofix.ci] apply automated fixes

`Field.value` used `bun.Semver.String` which treats inline data (<=8 bytes)
as null-terminated strings, truncating binary file content at the first 0x00
byte. Replace with a raw `[]const u8` slice into the input buffer.

Closes #27478

Co-Authored-By: Claude <noreply@anthropic.com>

docs/bundler/executables.mdx

@@ -228,16 +228,16 @@ To build for macOS x64:
 
 The order of the `--target` flag does not matter, as long as they're delimited by a `-`.
 
-| --target              | Operating System | Architecture | Modern | Baseline | Libc  |
-| --------------------- | ---------------- | ------------ | ------ | -------- | ----- |
-| bun-linux-x64         | Linux            | x64          | ✅     | ✅       | glibc |
-| bun-linux-arm64       | Linux            | arm64        | ✅     | N/A      | glibc |
-| bun-windows-x64       | Windows          | x64          | ✅     | ✅       | -     |
-| bun-windows-arm64     | Windows          | arm64        | ✅     | N/A      | -     |
-| bun-darwin-x64        | macOS            | x64          | ✅     | ✅       | -     |
-| bun-darwin-arm64      | macOS            | arm64        | ✅     | N/A      | -     |
-| bun-linux-x64-musl    | Linux            | x64          | ✅     | ✅       | musl  |
-| bun-linux-arm64-musl  | Linux            | arm64        | ✅     | N/A      | musl  |
+| --target             | Operating System | Architecture | Modern | Baseline | Libc  |
+| -------------------- | ---------------- | ------------ | ------ | -------- | ----- |
+| bun-linux-x64        | Linux            | x64          | ✅     | ✅       | glibc |
+| bun-linux-arm64      | Linux            | arm64        | ✅     | N/A      | glibc |
+| bun-windows-x64      | Windows          | x64          | ✅     | ✅       | -     |
+| bun-windows-arm64    | Windows          | arm64        | ✅     | N/A      | -     |
+| bun-darwin-x64       | macOS            | x64          | ✅     | ✅       | -     |
+| bun-darwin-arm64     | macOS            | arm64        | ✅     | N/A      | -     |
+| bun-linux-x64-musl   | Linux            | x64          | ✅     | ✅       | musl  |
+| bun-linux-arm64-musl | Linux            | arm64        | ✅     | N/A      | musl  |
 
 <Warning>
   On x64 platforms, Bun uses SIMD optimizations which require a modern CPU supporting AVX2 instructions. The `-baseline`

src/url.zig

@@ -976,7 +976,10 @@ pub const FormData = struct {
     }
 
     pub const Field = struct {
-        value: bun.Semver.String = .{},
+        /// Raw slice into the input buffer. Not using `bun.Semver.String` because
+        /// file bodies are binary data that can contain null bytes, which
+        /// Semver.String's inline storage treats as terminators.
+        value: []const u8 = "",
         filename: bun.Semver.String = .{},
         content_type: bun.Semver.String = .{},
         is_file: bool = false,
@@ -1088,7 +1091,7 @@ pub const FormData = struct {
             form: *jsc.DOMFormData,
 
             pub fn onEntry(wrap: *@This(), name: bun.Semver.String, field: Field, buf: []const u8) void {
-                const value_str = field.value.slice(buf);
+                const value_str = field.value;
                 var key = jsc.ZigString.initUTF8(name.slice(buf));
 
                 if (field.is_file) {
@@ -1278,7 +1281,7 @@ pub const FormData = struct {
             if (strings.endsWithComptime(body, "\r\n")) {
                 body = body[0 .. body.len - 2];
             }
-            field.value = subslicer.sub(body).value();
+            field.value = body;
             field.filename = filename orelse .{};
             field.is_file = is_file;
 

test/regression/issue/27478.test.ts

@@ -0,0 +1,120 @@
+import { expect, test } from "bun:test";
+
+// https://github.com/oven-sh/bun/issues/27478
+// Request.formData() truncates small binary files at first null byte
+test("multipart formdata preserves null bytes in small binary files", async () => {
+  const boundary = "----bun-null-byte-boundary";
+  const source = Buffer.from([0x1f, 0x8b, 0x08, 0x00]);
+  const payload = Buffer.concat([
+    Buffer.from(
+      `--${boundary}\r\n` +
+        `Content-Disposition: form-data; name="file"; filename="test.bin"\r\n` +
+        `Content-Type: application/octet-stream\r\n\r\n`,
+      "utf8",
+    ),
+    source,
+    Buffer.from(`\r\n--${boundary}--\r\n`, "utf8"),
+  ]);
+
+  const request = new Request("http://localhost/", {
+    method: "POST",
+    headers: { "content-type": `multipart/form-data; boundary=${boundary}` },
+    body: payload,
+  });
+
+  const form = await request.formData();
+  const file = form.get("file");
+  expect(file).toBeInstanceOf(File);
+
+  const parsed = new Uint8Array(await (file as File).arrayBuffer());
+  expect(Array.from(parsed)).toEqual(Array.from(source));
+  expect(parsed.byteLength).toBe(source.byteLength);
+});
+
+test("multipart formdata preserves files that are all null bytes", async () => {
+  const boundary = "----bun-test-boundary";
+  const source = Buffer.from([0x00, 0x00, 0x00, 0x00]);
+  const payload = Buffer.concat([
+    Buffer.from(
+      `--${boundary}\r\n` +
+        `Content-Disposition: form-data; name="file"; filename="zeros.bin"\r\n` +
+        `Content-Type: application/octet-stream\r\n\r\n`,
+      "utf8",
+    ),
+    source,
+    Buffer.from(`\r\n--${boundary}--\r\n`, "utf8"),
+  ]);
+
+  const request = new Request("http://localhost/", {
+    method: "POST",
+    headers: { "content-type": `multipart/form-data; boundary=${boundary}` },
+    body: payload,
+  });
+
+  const form = await request.formData();
+  const file = form.get("file");
+  expect(file).toBeInstanceOf(File);
+
+  const parsed = new Uint8Array(await (file as File).arrayBuffer());
+  expect(Array.from(parsed)).toEqual([0x00, 0x00, 0x00, 0x00]);
+  expect(parsed.byteLength).toBe(4);
+});
+
+test("multipart formdata preserves single null byte file", async () => {
+  const boundary = "----bun-test-boundary";
+  const source = Buffer.from([0x00]);
+  const payload = Buffer.concat([
+    Buffer.from(
+      `--${boundary}\r\n` +
+        `Content-Disposition: form-data; name="file"; filename="null.bin"\r\n` +
+        `Content-Type: application/octet-stream\r\n\r\n`,
+      "utf8",
+    ),
+    source,
+    Buffer.from(`\r\n--${boundary}--\r\n`, "utf8"),
+  ]);
+
+  const request = new Request("http://localhost/", {
+    method: "POST",
+    headers: { "content-type": `multipart/form-data; boundary=${boundary}` },
+    body: payload,
+  });
+
+  const form = await request.formData();
+  const file = form.get("file");
+  expect(file).toBeInstanceOf(File);
+
+  const parsed = new Uint8Array(await (file as File).arrayBuffer());
+  expect(Array.from(parsed)).toEqual([0x00]);
+  expect(parsed.byteLength).toBe(1);
+});
+
+test("multipart formdata preserves 8-byte binary with embedded nulls", async () => {
+  const boundary = "----bun-test-boundary";
+  // Exactly 8 bytes (max inline length of Semver.String) with nulls interspersed
+  const source = Buffer.from([0x01, 0x00, 0x02, 0x00, 0x03, 0x00, 0x04, 0x00]);
+  const payload = Buffer.concat([
+    Buffer.from(
+      `--${boundary}\r\n` +
+        `Content-Disposition: form-data; name="file"; filename="mixed.bin"\r\n` +
+        `Content-Type: application/octet-stream\r\n\r\n`,
+      "utf8",
+    ),
+    source,
+    Buffer.from(`\r\n--${boundary}--\r\n`, "utf8"),
+  ]);
+
+  const request = new Request("http://localhost/", {
+    method: "POST",
+    headers: { "content-type": `multipart/form-data; boundary=${boundary}` },
+    body: payload,
+  });
+
+  const form = await request.formData();
+  const file = form.get("file");
+  expect(file).toBeInstanceOf(File);
+
+  const parsed = new Uint8Array(await (file as File).arrayBuffer());
+  expect(Array.from(parsed)).toEqual([0x01, 0x00, 0x02, 0x00, 0x03, 0x00, 0x04, 0x00]);
+  expect(parsed.byteLength).toBe(8);
+});