fix(windows spawn): use Job Object to manage subprocesses of subprocesses

src/bun.js/api/bun/process.zig

@@ -1671,7 +1671,7 @@ pub fn spawnProcessWindows(
     uv_process_options.stdio_count = @intCast(stdio_containers.items.len);
 
     uv_process_options.exit_cb = &Process.onExitUV;
-    var process = Process.new(.{
+    const process = Process.new(.{
         .event_loop = options.windows.loop,
         .pid = 0,
     });
@@ -1716,6 +1716,13 @@ pub fn spawnProcessWindows(
         .extra_pipes = try std.ArrayList(WindowsSpawnResult.StdioResult).initCapacity(bun.default_allocator, options.extra_fds.len),
     };
 
+    // By putting this process in a Job Object, any child process will be caught
+    // so that killing this process will kill all children processes.
+    //
+    // It seems that just associating the process does the work neccecary.
+    if (bun.windows.CreateJobObjectA(null, null)) |job|
+        _ = bun.windows.AssignProcessToJobObject(job, process.poller.uv.process_handle);
+
     const result_stdios = .{ &result.stdin, &result.stdout, &result.stderr };
     inline for (0..3) |i| {
         const stdio = stdio_containers.items[i];

test/js/bun/spawn/empty.js

@@ -0,0 +1 @@
+// empty file

test/js/bun/spawn/job-object-bug.test.ts

@@ -0,0 +1,14 @@
+import { spawn } from "bun";
+import { it, expect } from "bun:test";
+import { bunEnv, bunExe } from "harness";
+import { join } from "node:path";
+
+it("does not hang", async () => {
+  const subprocess = spawn({
+    cmd: [bunExe(), "test", join(import.meta.dirname, "job-object-bug.ts")],
+    env: bunEnv,
+    stdio: ["ignore", "pipe", "pipe"],
+  });
+  await Bun.readableStreamToText(subprocess.stdout);
+  expect(await subprocess.exited).toBe(0);
+});

test/js/bun/spawn/job-object-bug.ts

@@ -0,0 +1,16 @@
+import { spawn } from "bun";
+import { bunEnv, bunExe } from "harness";
+import { join } from "node:path";
+
+// prior, this would hang on Windows if you ran this with a pipe
+
+const run = spawn({
+  cmd: [bunExe(), "--watch", join(import.meta.dirname, "empty.js")],
+  stdout: "inherit",
+  stderr: "inherit",
+  stdin: "ignore",
+  env: bunEnv,
+});
+await Bun.sleep(250);
+run.kill(9);
+await run.exited;