ci: install zsh for shell documentation checks

Author: EvanProgramming

.github/workflows/ci.yml

@@ -23,6 +23,8 @@ jobs:
 
     - name: Install dependencies
       run: |
+        sudo apt-get update
+        sudo apt-get install --no-install-recommends -y zsh
         python -m pip install --upgrade pip
         pip install -r requirements.txt
         pip install fastapi uvicorn

scripts/check_zsh_extras.py

@@ -4,6 +4,7 @@
 from __future__ import annotations
 
 import re
+import shutil
 import subprocess
 import sys
 from pathlib import Path
@@ -67,6 +68,8 @@ def _run_zsh(args: list[str], script: str) -> subprocess.CompletedProcess[str]:
 
 
 def _check_zsh() -> list[str]:
+    if shutil.which("zsh") is None:
+        return ["zsh executable not found; install zsh before running this check"]
     syntax = "pip install '.[web]'\npip install '.[all]'\n"
     parsed = _run_zsh(["-n"], syntax)
     if parsed.returncode: