Load plugins from entry points

Enables the loading of plugins via entry points. This should enable libraries to install and advertise their own plugins without requiring as much user configuration.

Closes #69

Author: abkfenris

docs/index.md

@@ -32,5 +32,6 @@ The following plugins provide XRLint's [inbuilt rules](rule-ref.md):
 - `xcube`: implementing the rules for 
   [xcube datasets](https://xcube.readthedocs.io/en/latest/cubespec.html).
   Note, this plugin is fully optional. You must manually configure 
-  it to apply its rules. It may be moved into a separate GitHub repo later. 
+  it to apply its rules. It may be moved into a separate GitHub repo later.
+- `acdd`: implements rules for [Attribute Convention for Data Discovery](https://wiki.esipfed.org/Attribute_Convention_for_Data_Discovery_1-3).
 

docs/start.md

@@ -66,6 +66,12 @@ rule configurations:
 
 You can add rules from plugins as well:
 
+!!! note inline end "Built in and auto-loading plugins"
+
+    The included plugins (such as `xcube` in the example configs here) and those from external libraries that are findable via [entry points](https://setuptools.pypa.io/en/latest/userguide/entry_point.html) do not need to be explicitly loaded.
+
+    Run `xrlint --print-config <dataset>` to view the loaded plugins and configured rules.
+
 ```yaml
 - recommended
 - plugins:

pyproject.toml

@@ -40,6 +40,11 @@ classifiers = [
   "Operating System :: MacOS",
 ]
 
+[project.entry-points."xrlint.rules"]
+core = "xrlint.plugins.core"
+xcube = "xrlint.plugins.xcube"
+acdd = "xrlint.plugins.acdd"
+
 [tool.setuptools.dynamic]
 version = {attr = "xrlint.__version__"}
 readme = {file = "README.md", content-type = "text/markdown"}

tests/cli/test_main.py

@@ -230,7 +230,9 @@ def test_print_config_option(self):
                 (
                     "{\n"
                     '  "plugins": {\n'
-                    '    "__core__": "xrlint.plugins.core:export_plugin"\n'
+                    '    "acdd": "xrlint.plugins.acdd:export_plugin",\n'
+                    '    "__core__": "xrlint.plugins.core:export_plugin",\n'
+                    '    "xcube": "xrlint.plugins.xcube:export_plugin"\n'
                     "  },\n"
                     '  "rules": {\n'
                     '    "var-units": 2\n'

tests/test_config.py

@@ -8,7 +8,7 @@
 import pytest
 import xarray as xr
 
-from xrlint.config import Config, ConfigObject, get_core_config_object
+from xrlint.config import Config, ConfigObject, get_entry_point_plugins
 from xrlint.constants import CORE_PLUGIN_NAME
 from xrlint.plugin import Plugin, new_plugin
 from xrlint.processor import ProcessorOp, define_processor
@@ -35,15 +35,15 @@ def test_defaults(self):
         self.assertEqual(None, config_obj.rules)
 
     def test_get_plugin(self):
-        config_obj = get_core_config_object()
+        config_obj = get_entry_point_plugins()
         plugin = config_obj.get_plugin(CORE_PLUGIN_NAME)
         self.assertIsInstance(plugin, Plugin)
 
-        with pytest.raises(ValueError, match="unknown plugin 'xcube'"):
-            config_obj.get_plugin("xcube")
+        with pytest.raises(ValueError, match="unknown plugin 'does-not-exist'"):
+            config_obj.get_plugin("does-not-exist")
 
     def test_get_rule(self):
-        config_obj = get_core_config_object()
+        config_obj = get_entry_point_plugins()
         rule = config_obj.get_rule("var-flags")
         self.assertIsInstance(rule, Rule)
 
@@ -195,7 +195,7 @@ def test_from_config_ok(self):
 
         config = Config.from_config(
             {"ignores": ["**/*.levels"]},
-            get_core_config_object(),
+            get_entry_point_plugins(),
             "recommended",
             {"rules": {"no-empty-chunks": 2}},
         )

tests/test_linter.py

@@ -28,7 +28,7 @@ def test_new_linter(self):
         self.assertEqual(1, len(linter.config.objects))
         config_obj = linter.config.objects[0]
         self.assertIsInstance(config_obj.plugins, dict)
-        self.assertEqual({CORE_PLUGIN_NAME}, set(config_obj.plugins.keys()))
+        self.assertIn(CORE_PLUGIN_NAME, config_obj.plugins)
         self.assertEqual(None, config_obj.rules)
 
     def test_new_linter_recommended(self):
@@ -38,7 +38,7 @@ def test_new_linter_recommended(self):
         config_obj_0 = linter.config.objects[0]
         config_obj_1 = linter.config.objects[1]
         self.assertIsInstance(config_obj_0.plugins, dict)
-        self.assertEqual({CORE_PLUGIN_NAME}, set(config_obj_0.plugins.keys()))
+        self.assertIn(CORE_PLUGIN_NAME, config_obj_0.plugins)
         self.assertIsInstance(config_obj_1.rules, dict)
         self.assertIn("coords-for-dims", config_obj_1.rules)
 
@@ -49,7 +49,7 @@ def test_new_linter_all(self):
         config_obj_0 = linter.config.objects[0]
         config_obj_1 = linter.config.objects[1]
         self.assertIsInstance(config_obj_0.plugins, dict)
-        self.assertEqual({CORE_PLUGIN_NAME}, set(config_obj_0.plugins.keys()))
+        self.assertIn(CORE_PLUGIN_NAME, config_obj_0.plugins)
         self.assertIsInstance(config_obj_1.rules, dict)
         self.assertIn("coords-for-dims", config_obj_1.rules)
 

xrlint/cli/engine.py

@@ -22,7 +22,7 @@
     DEFAULT_OUTPUT_FORMAT,
     INIT_CONFIG_YAML,
 )
-from xrlint.config import Config, ConfigLike, ConfigObject, get_core_config_object
+from xrlint.config import Config, ConfigLike, ConfigObject, get_entry_point_plugins
 from xrlint.formatter import FormatterContext
 from xrlint.formatters import export_formatters
 from xrlint.linter import Linter
@@ -117,7 +117,7 @@ def init_config(self, *extra_configs: ConfigLike) -> None:
             if file_config is None:
                 click.echo("Warning: no configuration file found.")
 
-        core_config_obj = get_core_config_object()
+        core_config_obj = get_entry_point_plugins()
         core_config_obj.plugins.update(plugins)
 
         base_configs = []

xrlint/config.py

@@ -51,13 +51,37 @@ def get_core_plugin() -> "Plugin":
     return export_plugin()
 
 
-def get_core_config_object() -> "ConfigObject":
-    """Create a configuration object that includes the core plugin.
+def plugins_from_entry_points() -> dict[str, "Plugin"]:
+    """Load plugins from entry points.
+
+    Returns:
+        A dictionary mapping plugin names to plugin instances.
+    """
+    from importlib.metadata import entry_points
+
+    plugins = {}
+
+    for ep in entry_points(group="xrlint.rules"):
+        try:
+            plugin_module = ep.load()
+            plugin = plugin_module.export_plugin()
+            plugins[plugin.meta.name] = plugin
+        except Exception as e:
+            breakpoint()
+            raise ValueError(
+                f"failed to load xrlint plugin from entry point {ep.name!r}: {e}"
+            ) from e
+
+    return plugins
+
+
+def get_entry_point_plugins() -> "ConfigObject":
+    """Create a configuration object that includes the plugins loaded from entry points.
 
     Returns:
         A new `Config` object
     """
-    return ConfigObject(plugins={CORE_PLUGIN_NAME: get_core_plugin()})
+    return ConfigObject(plugins=plugins_from_entry_points())
 
 
 def split_config_spec(config_spec: str) -> tuple[str, str]:
@@ -379,7 +403,7 @@ def from_config(
             new_objects = None
             if isinstance(config_like, str):
                 if CORE_PLUGIN_NAME not in plugins:
-                    plugins.update({CORE_PLUGIN_NAME: get_core_plugin()})
+                    plugins.update(plugins_from_entry_points())
                 new_objects = cls._get_named_config(config_like, plugins).objects
             elif isinstance(config_like, Config):
                 new_objects = config_like.objects

xrlint/linter.py

@@ -8,7 +8,7 @@
 
 import xarray as xr
 
-from xrlint.config import Config, ConfigLike, get_core_config_object
+from xrlint.config import Config, ConfigLike, get_entry_point_plugins
 from xrlint.result import Result
 
 from ._linter.validate import new_fatal_message, validate_dataset
@@ -30,7 +30,7 @@ def new_linter(*configs: ConfigLike, **config_props: Any) -> "Linter":
     Returns:
         A new linter instance
     """
-    return Linter(get_core_config_object(), *configs, **config_props)
+    return Linter(get_entry_point_plugins(), *configs, **config_props)
 
 
 class Linter: