Use transformers instead of validators for Argument

Author: DanielNoord

pylint/config/argument.py

@@ -8,24 +8,30 @@
 """
 
 
-from typing import Any, Callable, Dict, List, Optional, Union
+from typing import Callable, Dict, List, Optional, Union
 
 from pylint import utils as pylint_utils
 
 _ArgumentTypes = Union[str, List[str]]
 """List of possible argument types."""
 
 
-def _csv_validator(value: Union[str, List[str]]) -> List[str]:
-    """Validates a comma separated string."""
+def _csv_transformer(value: str) -> List[str]:
+    """Transforms a comma separated string."""
     return pylint_utils._check_csv(value)
 
 
-_ASSIGNMENT_VALIDATORS: Dict[str, Callable[[Any], _ArgumentTypes]] = {
+_TYPE_TRANSFORMERS: Dict[str, Callable[[str], _ArgumentTypes]] = {
     "choice": str,
-    "csv": _csv_validator,
+    "csv": _csv_transformer,
 }
-"""Validators for all assignment types."""
+"""Type transformers for all argument types.
+
+A transformer should accept a string and return one of the supported
+Argument types. It will only be called when parsing 1) command-line,
+2) configuration files and 3) a string default value.
+Non-string default values are assumed to be of the correct type.
+"""
 
 
 class _Argument:
@@ -52,10 +58,10 @@ def __init__(
         self.action = action
         """The action to perform with the argument."""
 
-        self.type = _ASSIGNMENT_VALIDATORS[arg_type]
-        """A validator function that returns and checks the type of the argument."""
+        self.type = _TYPE_TRANSFORMERS[arg_type]
+        """A transformer function that returns a transformed type of the argument."""
 
-        self.default = self.type(default)
+        self.default = default
         """The default value of the argument."""
 
         self.choices = choices