fix: Fix zombie process spawning from shell PATH resolution (#1435)

Author: charlesvien

apps/code/src/main/utils/fixPath.ts

@@ -3,13 +3,24 @@
  * (/usr/bin:/bin:/usr/sbin:/sbin) instead of the user's shell PATH which
  * includes /opt/homebrew/bin, ~/.local/bin, etc.
  *
- * This reads the PATH from the user's default shell (in interactive login mode)
- * and applies it to process.env.PATH so child processes have access to
+ * This reads the PATH from the user's default shell (in login mode) and
+ * applies it to process.env.PATH so child processes have access to
  * user-installed binaries.
+ *
+ * IMPORTANT: We use `-lc` (login, non-interactive) instead of `-ilc`
+ * (interactive login) to avoid loading the user's full .zshrc which may
+ * include heavy plugins (Oh My Zsh, NVM, thefuck, etc.) that spawn
+ * subprocesses and cause zombie process chains when the timeout kills
+ * only the parent shell.
+ *
+ * See: https://github.com/PostHog/code/issues/1399
  */
 
-import { execSync } from "node:child_process";
+import { spawnSync } from "node:child_process";
+import { existsSync, mkdirSync, readFileSync, writeFileSync } from "node:fs";
 import { userInfo } from "node:os";
+import { dirname, join } from "node:path";
+import { app } from "electron";
 
 const DELIMITER = "_SHELL_ENV_DELIMITER_";
 
@@ -25,6 +36,9 @@ const ANSI_REGEX =
   // biome-ignore lint/suspicious/noControlCharactersInRegex: intentional for ANSI stripping
   /[\u001B\u009B][[\]()#;?]*(?:(?:(?:[a-zA-Z\d]*(?:;[-a-zA-Z\d/#&.:=?%@~_]*)*)?\u0007)|(?:(?:\d{1,4}(?:;\d{0,4})*)?[\dA-PR-TZcf-ntqry=><~]))/g;
 
+/** Max age of cached PATH before re-resolving (1 hour) */
+const CACHE_MAX_AGE_MS = 60 * 60 * 1000;
+
 function stripAnsi(str: string): string {
   return str.replace(ANSI_REGEX, "");
 }
@@ -50,20 +64,75 @@ function detectDefaultShell(): string {
   return process.env.SHELL || "/bin/sh";
 }
 
+function getCachePath(): string {
+  return join(app.getPath("userData"), "shell-env-cache.json");
+}
+
+function readCachedPath(): string | undefined {
+  try {
+    const cachePath = getCachePath();
+    if (!existsSync(cachePath)) {
+      return undefined;
+    }
+
+    const raw = readFileSync(cachePath, "utf-8");
+    const cache = JSON.parse(raw) as { path: string; timestamp: number };
+
+    if (Date.now() - cache.timestamp > CACHE_MAX_AGE_MS) {
+      return undefined;
+    }
+
+    return cache.path;
+  } catch {
+    return undefined;
+  }
+}
+
+function writeCachedPath(resolvedPath: string): void {
+  try {
+    const cachePath = getCachePath();
+    const dir = dirname(cachePath);
+    if (!existsSync(dir)) {
+      mkdirSync(dir, { recursive: true });
+    }
+    writeFileSync(
+      cachePath,
+      JSON.stringify({ path: resolvedPath, timestamp: Date.now() }),
+      "utf-8",
+    );
+  } catch {
+    // Cache write failure is non-fatal
+  }
+}
+
 function executeShell(shell: string): string | undefined {
   const command = `echo -n "${DELIMITER}"; env; echo -n "${DELIMITER}"; exit`;
 
   try {
-    return execSync(`${shell} -ilc '${command}'`, {
+    const result = spawnSync(shell, ["-lc", command], {
       encoding: "utf-8",
       timeout: 5000,
       stdio: ["ignore", "pipe", "ignore"],
+      // Kill the entire process group on timeout, not just the parent shell.
+      // This prevents orphaned children (node -v, printf, tail, sed) from
+      // surviving as zombies.
+      killSignal: "SIGKILL",
       env: {
         ...process.env,
         // Disable Oh My Zsh auto-update which can block
         DISABLE_AUTO_UPDATE: "true",
+        // Signal to user's shell config that we're resolving the environment.
+        // Users with heavy configs can check this and fast-exit:
+        //   [[ -n "$POSTHOG_CODE_RESOLVING_ENVIRONMENT" ]] && return
+        POSTHOG_CODE_RESOLVING_ENVIRONMENT: "1",
       },
     });
+
+    if (result.status !== 0 && !result.stdout) {
+      return undefined;
+    }
+
+    return result.stdout || undefined;
   } catch {
     return undefined;
   }
@@ -110,11 +179,20 @@ export function fixPath(): void {
     return;
   }
 
+  // Try cached PATH first (instant, no shell spawn)
+  const cached = readCachedPath();
+  if (cached) {
+    process.env.PATH = cached;
+    return;
+  }
+
   const shell = detectDefaultShell();
   const shellPath = getShellPath(shell);
 
   if (shellPath) {
-    process.env.PATH = stripAnsi(shellPath);
+    const cleaned = stripAnsi(shellPath);
+    process.env.PATH = cleaned;
+    writeCachedPath(cleaned);
   } else {
     process.env.PATH = buildFallbackPath();
   }