Function probeLoginShellPath

packages/kaos/src/login-shell-path.ts:47–79

(deps: LoginShellPathDeps)

 * error, timeout, no PATH in the output).
 */
export async function probeLoginShellPath(deps: LoginShellPathDeps): Promise<string | undefined> {
  if (deps.platform === 'win32') return undefined;
  // A set-but-blank $SHELL (some daemon/launchd envs) must also fall back.
  const envShell = deps.env['SHELL']?.trim();
  const shell = envShell === undefined || envShell.length === 0 ? deps.userShell() : envShell;
  if (shell === undefined || shell.length === 0) return undefined;

  // `env` prints the resolved environment in every shell dialect, unlike
  // `echo $PATH`, which fish would join with spaces. Invoke it by absolute
  // path: a bare `env` resolves through the inherited PATH — which may
  // carry cwd-dependent components — from the workspace cwd, so a
  // repo-planted `env` binary could run at session startup and feed us an
  // arbitrary PATH. The absolute path also bypasses profile function
  // shadowing, and /usr/bin/env is guaranteed on every mainstream POSIX
  // system (it is the canonical shebang interpreter path).
  const stdout = await deps.execFileText(
    shell,
    ['-l', '-c', '/usr/bin/env'],
    LOGIN_SHELL_ENV_TIMEOUT_MS,
  );
  if (stdout === undefined) return undefined;

  // Profile output lands on stdout before `env` runs, so keep the last
  // PATH= line.
  let path: string | undefined;
  for (const line of stdout.split('\n')) {
    if (line.startsWith('PATH=')) {
      path = line.slice('PATH='.length).trim();
    }
  }
  if (path === undefined || path.length === 0) return undefined;
  return path;
}

/**
 * Union of the current PATH and the login-shell PATH: the current PATH