fix: make JujuConfig validation accept empty options (#1424)

fixes #1398

charmcraft/metafiles/config.py

@@ -53,6 +53,14 @@ def parse_config_yaml(charm_dir: pathlib.Path, allow_broken=False) -> Optional[J
     except OSError as exc:
         raise CraftError(f"Cannot read the {JUJU_CONFIG_FILENAME} file: {exc!r}") from exc
 
+    if allow_broken and (not isinstance(config, dict) or not config.get("options")):
+        emit.progress(
+            "'config.yaml' is not a valid config file.",
+            permanent=True,
+        )
+        emit.debug(f"Ignoring {JUJU_CONFIG_FILENAME}")
+        return None
+
     emit.debug(f"Validating {JUJU_CONFIG_FILENAME}")
     try:
         return JujuConfig.parse_obj(config)

charmcraft/models/config.py

@@ -16,7 +16,7 @@
 
 """Charmcraft Juju Config pydantic model."""
 
-from typing import Dict, Optional
+from typing import Any, Dict, Optional
 
 import pydantic
 
@@ -29,11 +29,15 @@ class JujuConfig(ModelConfigDefaults):
     See also: https://juju.is/docs/sdk/config
     """
 
-    options: Optional[Dict[str, Dict]]
+    options: Optional[Dict[str, Dict[str, Any]]]
 
     @pydantic.validator("options", pre=True)
     def validate_actions(cls, options):
         """Verify options section."""
+        if options is None:
+            return None
+        if not isinstance(options, dict):
+            raise ValueError("'options' is not a dictionary")
         for name, option in options.items():
             if not isinstance(option, dict):
                 raise ValueError(f"'{name}' is not a dictionary")

tests/test_models.py

@@ -1194,7 +1194,18 @@ def test_load_config_in_config_yaml(tmp_path, prepare_charmcraft_yaml, prepare_c
     }
 
 
-def test_load_bad_config_in_config_yaml(tmp_path, prepare_charmcraft_yaml, prepare_config_yaml):
+@pytest.mark.parametrize(
+    "config_yaml",
+    [
+        "",
+        "options:",
+        "options:\n  test-int:",
+        "options: not a dict",
+    ],
+)
+def test_load_bad_config_in_config_yaml(
+    tmp_path, prepare_charmcraft_yaml, prepare_config_yaml, config_yaml
+):
     """Load a bad config in config.yaml. Should not raise an error since check unenforced."""
     prepare_charmcraft_yaml(
         dedent(
@@ -1206,14 +1217,7 @@ def test_load_bad_config_in_config_yaml(tmp_path, prepare_charmcraft_yaml, prepa
             """
         ),
     )
-    prepare_config_yaml(
-        dedent(
-            """
-            options:
-              test-int:
-            """
-        ),
-    )
+    prepare_config_yaml(config_yaml)
     config = load(tmp_path)
 
     assert config.config is None