fix(scripts): kill managed child trees on windows

scripts/lib/managed-child-process.mjs

@@ -1,5 +1,5 @@
 // Runs child commands with process-group signal forwarding and Windows shell normalization.
-import { spawn } from "node:child_process";
+import { spawn, spawnSync } from "node:child_process";
 import { constants as osConstants } from "node:os";
 import { buildCmdExeCommandLine } from "../windows-cmd-helpers.mjs";
 
@@ -22,14 +22,19 @@ export function signalExitCode(signal) {
 /**
  * @param {import("node:child_process").ChildProcess} child
  * @param {NodeJS.Signals} [signal]
+ * @param {{ platform?: NodeJS.Platform; runTaskkill?: typeof spawnSync }} [options]
  */
-function terminateManagedChild(child, signal = "SIGTERM") {
+export function terminateManagedChild(
+  child,
+  signal = "SIGTERM",
+  { platform = process.platform, runTaskkill = spawnSync } = {},
+) {
   if (!child.pid) {
     return;
   }
 
   try {
-    if (process.platform !== "win32") {
+    if (platform !== "win32") {
       process.kill(-child.pid, signal);
       return;
     }
@@ -44,6 +49,17 @@ function terminateManagedChild(child, signal = "SIGTERM") {
     return;
   }
 
+  if (platform === "win32") {
+    const args = ["/PID", String(child.pid), "/T"];
+    if (signal === "SIGKILL") {
+      args.push("/F");
+    }
+    const result = runTaskkill("taskkill", args, { stdio: "ignore" });
+    if (!result?.error && result?.status === 0) {
+      return;
+    }
+  }
+
   child.kill(signal);
 }
 

test/scripts/managed-child-process.test.ts

@@ -4,11 +4,12 @@ import fs from "node:fs";
 import path from "node:path";
 import { setTimeout as delay } from "node:timers/promises";
 import { pathToFileURL } from "node:url";
-import { describe, expect, it } from "vitest";
+import { describe, expect, it, vi } from "vitest";
 import {
   createManagedCommandSpawnSpec,
   runManagedCommand,
   signalExitCode,
+  terminateManagedChild,
 } from "../../scripts/lib/managed-child-process.mjs";
 import { createScriptTestHarness } from "./test-helpers.js";
 
@@ -110,6 +111,31 @@ describe("managed-child-process", () => {
     ).toThrow("unsafe Windows cmd.exe argument detected");
   });
 
+  it("signals Windows managed process trees with taskkill", () => {
+    const child = {
+      kill: vi.fn(),
+      pid: 12345,
+    };
+    const runTaskkill = vi.fn(() => ({ error: undefined, status: 0 }));
+
+    terminateManagedChild(child, "SIGTERM", {
+      platform: "win32",
+      runTaskkill,
+    });
+    expect(runTaskkill).toHaveBeenNthCalledWith(1, "taskkill", ["/PID", "12345", "/T"], {
+      stdio: "ignore",
+    });
+
+    terminateManagedChild(child, "SIGKILL", {
+      platform: "win32",
+      runTaskkill,
+    });
+    expect(runTaskkill).toHaveBeenNthCalledWith(2, "taskkill", ["/PID", "12345", "/T", "/F"], {
+      stdio: "ignore",
+    });
+    expect(child.kill).not.toHaveBeenCalled();
+  });
+
   it("shares process signal listeners across parallel managed commands", async () => {
     const signals = ["SIGHUP", "SIGINT", "SIGTERM"] as const;
     const baseline = new Map(signals.map((signal) => [signal, process.listenerCount(signal)]));