Make config parsing more resilient

src/nomadic/util/cli.py

@@ -11,7 +11,12 @@
     find_workspace_root,
     check_if_workspace_root,
 )
-from nomadic.util.config import load_config, default_config_path
+from nomadic.util.config import (
+    InvalidConfigError,
+    get_command_defaults,
+    load_config,
+    default_config_path,
+)
 
 WORKSPACE_OPTION_KEY = "workspace"
 
@@ -122,8 +127,24 @@ def load_defaults_from_config(ctx: click.Context, command: Optional[str] = None)
     config_path = os.path.join(workspace.path, default_config_path)
     if os.path.isfile(config_path):
         config = load_config(config_path)
-        defaults = config.get("defaults", {})
-        defaults = defaults | config.get(command, {}).get("defaults", {})
+        if not config:
+            # When empty dict or non, the config is empty
+            return
+        if not isinstance(config, dict):
+            if not ctx.resilient_parsing:
+                raise click.UsageError(
+                    f"Invalid config at {config_path}: config is not a dict."
+                )
+            else:
+                return
+        try:
+            defaults = get_command_defaults(config, command)
+        except InvalidConfigError as e:
+            if not ctx.resilient_parsing:
+                raise click.UsageError(f"Invalid config at {config_path}: {e}")
+            else:
+                return
+
         if defaults:
             if not ctx.resilient_parsing:
                 # Don't print defaults if parsing is resilient, as this is used for shell completion

src/nomadic/util/config.py

@@ -1,4 +1,5 @@
 from functools import reduce
+from typing import Optional
 
 from yaml import dump, load
 
@@ -11,6 +12,12 @@
 default_config_path = ".config.yaml"
 
 
+class InvalidConfigError(Exception):
+    """Raised when the config is invalid"""
+
+    pass
+
+
 def load_config(config_path: str) -> dict:
     """
     Load configuration from a YAML file.
@@ -62,3 +69,25 @@ def get_config_value(d: dict, keys: list, default=None):
         reduce(lambda acc, k: acc.get(k, {}) if isinstance(acc, dict) else {}, keys, d)
         or default
     )
+
+
+def get_command_defaults(config: dict, command: Optional[str]) -> dict:
+    defaults = must_get_dict(config, "defaults", "defaults should be a dict")
+    if command is not None:
+        command_config = must_get_dict(
+            config, command, f"{command} config should be a dict"
+        )
+        command_defaults = must_get_dict(
+            command_config, "defaults", f"{command} defaults should be a dict"
+        )
+        defaults = defaults | command_defaults
+    return defaults
+
+
+def must_get_dict(d: dict, key: str, message: str) -> dict:
+    value = d.get(key, {})
+    if value is None:
+        value = {}
+    if not isinstance(value, dict):
+        raise InvalidConfigError(message)
+    return value

src/nomadic/util/config_test.py

@@ -1,6 +1,11 @@
 import pytest
 
-from nomadic.util.config import get_config_value, set_config_value
+from nomadic.util.config import (
+    InvalidConfigError,
+    get_command_defaults,
+    get_config_value,
+    set_config_value,
+)
 
 
 @pytest.mark.parametrize(
@@ -28,3 +33,33 @@ def test_set_config_value_table(keys, value, expected):
     set_config_value(d, keys, value)
     assert get_config_value(d, keys) == value
     assert d == expected
+
+
+@pytest.mark.parametrize(
+    "config, command, expected",
+    [
+        ({}, None, {}),
+        ({}, "test", {}),
+        ({"defaults": None}, "test", {}),
+        ({"defaults": {"foo": "bar"}}, "test", {"foo": "bar"}),
+        (
+            {"defaults": {"foo": "bar"}, "test": {"defaults": {"this": "that"}}},
+            "test",
+            {"foo": "bar", "this": "that"},
+        ),
+    ],
+)
+def test_get_command_defaults(config, command, expected):
+    assert get_command_defaults(config, command) == expected
+
+
+@pytest.mark.parametrize(
+    "config, command",
+    [
+        ({"defaults": 5}, None),
+        ({"defaults": {}, "test": 5}, "test"),
+    ],
+)
+def test_get_command_defaults_invalid_configs(config, command):
+    with pytest.raises(InvalidConfigError):
+        get_command_defaults(config, command)