test: stabilize stale-pid ancestor override

(cherry picked from commit 4e25479cb2)

src/infra/restart-stale-pids.test.ts

@@ -185,24 +185,19 @@ describe.skipIf(isWindows)("restart-stale-pids", () => {
   afterEach(() => {
     __testing.setSleepSyncOverride(null);
     __testing.setDateNowOverride(null);
+    __testing.setParentPidOverride(null);
     vi.restoreAllMocks();
   });
 
-  // Temporarily rewrites `process.ppid` for a block of test code. Used by the
+  // Temporarily overrides the parent PID for a block of test code. Used by the
   // ancestor-exclusion tests to drive the real `getSelfAndAncestorPidsSync`
-  // walk without installing a runtime-reachable override on the module. Node
-  // always exposes `process.ppid` as an own property so the captured
-  // descriptor is non-null in practice; the `if (orig)` guard is defensive
-  // against a broken environment, not a reachable branch.
+  // walk without depending on runtime-specific `process.ppid` descriptors.
   function withStubbedPpid<T>(ppid: number, fn: () => T): T {
-    const orig = Object.getOwnPropertyDescriptor(process, "ppid");
-    Object.defineProperty(process, "ppid", { value: ppid, configurable: true });
+    __testing.setParentPidOverride(() => ppid);
     try {
       return fn();
     } finally {
-      if (orig) {
-        Object.defineProperty(process, "ppid", orig);
-      }
+      __testing.setParentPidOverride(null);
     }
   }
 

src/infra/restart-stale-pids.ts

@@ -45,6 +45,7 @@ const MAX_ANCESTOR_WALK_DEPTH = 32;
 const restartLog = createSubsystemLogger("restart");
 let sleepSyncOverride: ((ms: number) => void) | null = null;
 let dateNowOverride: (() => number) | null = null;
+let parentPidOverride: (() => number) | null = null;
 
 function getTimeMs(): number {
   return dateNowOverride ? dateNowOverride() : Date.now();
@@ -70,6 +71,10 @@ function sleepSync(ms: number): void {
   }
 }
 
+function getParentPid(): number {
+  return parentPidOverride ? parentPidOverride() : process.ppid;
+}
+
 /**
  * Read a single ancestor PID from `/proc/<pid>/status` on Linux.
  * Returns null on any failure (non-Linux platform, restricted /proc, race
@@ -135,7 +140,7 @@ function readParentPidFromProc(pid: number): number | null {
  */
 function getSelfAndAncestorPidsSync(): Set<number> {
   const pids = new Set<number>([process.pid]);
-  const immediateParent = process.ppid;
+  const immediateParent = getParentPid();
   if (!Number.isFinite(immediateParent) || immediateParent <= 0) {
     return pids;
   }
@@ -553,6 +558,9 @@ export const __testing = {
   setDateNowOverride(fn: (() => number) | null) {
     dateNowOverride = fn;
   },
+  setParentPidOverride(fn: (() => number) | null) {
+    parentPidOverride = fn;
+  },
   /** Invoke sleepSync directly (bypasses the override) for unit-testing the real Atomics path. */
   callSleepSyncRaw: sleepSync,
 };