test: Ensure pre-24.2 custom modules work (#6034)

tests/integration_tests/assets/dropins/cc_custom_module_24_1.py

@@ -0,0 +1,42 @@
+# This file is part of cloud-init. See LICENSE file for license information.
+"""This was the canonical example module from 24.1
+
+Ensure cloud-init still supports it."""
+
+import logging
+
+from cloudinit.cloud import Cloud
+from cloudinit.config import Config
+from cloudinit.config.schema import MetaSchema, get_meta_doc
+from cloudinit.distros import ALL_DISTROS
+from cloudinit.settings import PER_INSTANCE
+
+MODULE_DESCRIPTION = """\
+Description that will be used in module documentation.
+
+This will likely take multiple lines.
+"""
+
+LOG = logging.getLogger(__name__)
+
+meta: MetaSchema = {
+    "id": "cc_example",
+    "name": "Example Module",
+    "title": "Shows how to create a module",
+    "description": MODULE_DESCRIPTION,
+    "distros": [ALL_DISTROS],
+    "frequency": PER_INSTANCE,
+    "activate_by_schema_keys": ["example_key, example_other_key"],
+    "examples": [
+        "example_key: example_value",
+        "example_other_key: ['value', 2]",
+    ],
+}  # type: ignore
+
+__doc__ = get_meta_doc(meta)
+
+
+def handle(name: str, cfg: Config, cloud: Cloud, args: list) -> None:
+    LOG.debug(f"Hi from module {name}")  # noqa: G004
+    # Add one more line for easier testing
+    print("Hello from module")

tests/integration_tests/dropins/test_custom_modules.py

@@ -0,0 +1,28 @@
+# This file is part of cloud-init. See LICENSE file for license information.
+
+import pytest
+
+from tests.integration_tests import releases
+from tests.integration_tests.instances import IntegrationInstance
+from tests.integration_tests.releases import IS_UBUNTU
+from tests.integration_tests.util import ASSETS_DIR
+
+
+@pytest.mark.skipif(
+    not IS_UBUNTU, reason="module dir tested is ubuntu-specific"
+)
+def test_custom_module_24_1(client: IntegrationInstance):
+    """Ensure that modifications to cloud-init don't break old custom modules.
+
+    24.1 had documentation that differs from current best practices. We want
+    to ensure modules created from this documentation still work:
+    https://docs.cloud-init.io/en/24.1/development/module_creation.html
+    """
+    client.push_file(
+        ASSETS_DIR / "dropins/cc_custom_module_24_1.py",
+        "/usr/lib/python3/dist-packages/cloudinit/config/cc_custom_module_24_1.py",
+    )
+    output = client.execute("cloud-init single --name cc_custom_module_24_1")
+    if releases.CURRENT_RELEASE >= releases.PLUCKY:
+        assert "The 'get_meta_doc()' function is deprecated" in output
+    assert "Hello from module" in output