Add simple validation check for decorator

Author: ArBridgeman

exasol/toolbox/config.py

@@ -1,3 +1,4 @@
+import inspect
 from typing import (
     Annotated,
 )
@@ -10,14 +11,30 @@
     computed_field,
 )
 
+from exasol.toolbox.nox.plugin import PLUGIN_ATTR_NAME
 from exasol.toolbox.util.version import Version
 
 
+def validate_plugin_hook(plugin_class: object):
+    """
+    Checks all methods in a class for at least one specific pluggy hookimpl marker.
+    Raises ValueError if no methods are found with the marker.
+    """
+    for name, method in inspect.getmembers(plugin_class, inspect.isroutine):
+        if hasattr(method, PLUGIN_ATTR_NAME):
+            return True
+    raise ValueError(
+        f"No methods in {plugin_class.__name__} were found to be decorated"
+        "with `@hookimpl`"
+    )
+
+
 def valid_version_string(version_string: str) -> str:
     Version.from_string(version_string)
     return version_string
 
 
+ValidPluginHook = Annotated[type[object], AfterValidator(validate_plugin_hook)]
 ValidVersionStr = Annotated[str, AfterValidator(valid_version_string)]
 
 DEFAULT_EXCLUDED_PATHS = {
@@ -68,7 +85,7 @@ class BaseConfig(BaseModel):
         `exasol.toolbox.config.DEFAULT_EXCLUDED_PATHS`.
         """,
     )
-    plugins: tuple[object, ...] = Field(
+    plugins: tuple[ValidPluginHook, ...] = Field(
         default=(),
         description="""
         This is used to provide hooks to extend one or more of the Nox tasks provided

exasol/toolbox/nox/plugin.py

@@ -1,6 +1,7 @@
 import pluggy
 
 _PLUGIN_MARKER = "python-toolbox-nox"
+PLUGIN_ATTR_NAME = f"{_PLUGIN_MARKER}_impl"
 hookspec = pluggy.HookspecMarker("python-toolbox-nox")
 hookimpl = pluggy.HookimplMarker("python-toolbox-nox")
 

test/unit/config_test.py

@@ -6,6 +6,8 @@
     BaseConfig,
     valid_version_string,
 )
+from exasol.toolbox.nox.plugin import hookimpl
+from exasol.toolbox.util.version import Version
 
 
 class TestBaseConfig:
@@ -86,3 +88,29 @@ def test_pyupgrade_argument(minimum_python_version):
 def test_excluded_python_paths(add_to_excluded_python_paths, expected):
     conf = BaseConfig(add_to_excluded_python_paths=add_to_excluded_python_paths)
     assert sorted(conf.excluded_python_paths) == sorted(expected)
+
+
+class WithHook:
+    @hookimpl
+    def prepare_release_update_version(self, session, config, version: Version) -> None:
+        print("This is a simple, silly hook.")
+
+
+class WithoutHook:
+    def prepare_release_update_version(self, session, config, version: Version) -> None:
+        print("This is not a properly prepared hook.")
+
+
+class TestPlugins:
+    @staticmethod
+    def test_works_when_empty():
+        BaseConfig(plugins=())
+
+    @staticmethod
+    def test_works_for_hook(capsys):
+        BaseConfig(plugins=(WithHook,))
+
+    @staticmethod
+    def test_raises_exception_without_hook():
+        with pytest.raises(ValueError, match="with `@hookimpl`"):
+            BaseConfig(plugins=(WithoutHook,))