fix: allow non-Compose commits on Docker-free hosts [skip ci]

actions/utils/lint-docker-compose.py

@@ -12,8 +12,6 @@ def run(ctx, args):
     log, s = ctx.log, ctx.sys
     repo = ctx.paths.repo_root
     rc_ip = _validate_anchor_ips(ctx)
-    if not shutil.which("docker"):
-        log.error("docker is not installed or not in PATH."); return rc_ip or 1
 
     files_string, targets = "", ["."]
     if args.hook:
@@ -25,6 +23,9 @@ def run(ctx, args):
             log.info("No staged docker-compose files to lint."); return rc_ip
         targets = [f"/workdir/{f}" for f in files_string.splitlines()]
 
+    if not shutil.which("docker"):
+        log.error("docker is not installed or not in PATH."); return rc_ip or 1
+
     log.info("Running dclint --fix (via docker)...")
     env_args = []
     for k in ("HTTP_PROXY", "HTTPS_PROXY", "http_proxy", "https_proxy", "NO_PROXY", "no_proxy"):

tests/test_compose_hook.py

@@ -0,0 +1,37 @@
+import importlib.util
+from pathlib import Path
+import subprocess
+import tempfile
+from types import SimpleNamespace
+import unittest
+from unittest.mock import Mock, patch
+from engine.lib.sys import Sys
+
+spec = importlib.util.spec_from_file_location('compose_lint', Path(__file__).resolve().parents[1] / 'actions/utils/lint-docker-compose.py')
+lint = importlib.util.module_from_spec(spec)
+spec.loader.exec_module(lint)
+
+
+class HookTests(unittest.TestCase):
+    def setUp(self):
+        self.tmp = tempfile.TemporaryDirectory()
+        self.addCleanup(self.tmp.cleanup)
+        self.repo = Path(self.tmp.name)
+        subprocess.run(['git', 'init', '-q', str(self.repo)], check=True)
+        self.log = Mock()
+        self.ctx = SimpleNamespace(log=self.log, sys=Sys(self.log), node=None,
+                                   paths=SimpleNamespace(repo_root=str(self.repo), compositions=str(self.repo / 'compositions')))
+
+    def stage(self, name, content):
+        (self.repo / name).write_text(content)
+        subprocess.run(['git', '-C', str(self.repo), 'add', name], check=True)
+
+    def test_documentation_commit_does_not_require_docker(self):
+        self.stage('README.md', 'Documentation\n')
+        with patch.object(lint.shutil, 'which', return_value=None):
+            self.assertEqual(lint.run(self.ctx, SimpleNamespace(hook=True)), 0)
+
+    def test_compose_change_still_requires_docker(self):
+        self.stage('docker-compose.yml', 'services: {}\n')
+        with patch.object(lint.shutil, 'which', return_value=None):
+            self.assertNotEqual(lint.run(self.ctx, SimpleNamespace(hook=True)), 0)