Bugfix - extend ``magic-value-comparison`` support for parsing numerical types and `\\` in rcfile configuration (#7880)

1 files changed, 34 insertions, 3 deletions

diff --git a/pylint/extensions/magic_value.py b/pylint/extensions/magic_value.py
index 161bb2c95..7cfb410ae 100644
--- a/pylint/extensions/magic_value.py
+++ b/pylint/extensions/magic_value.py
@@ -6,6 +6,7 @@
 
 from __future__ import annotations
 
+from re import match as regex_match
 from typing import TYPE_CHECKING
 
 from astroid import nodes
@@ -37,11 +38,31 @@ class MagicValueChecker(BaseChecker):
                 "default": (0, -1, 1, "", "__main__"),
                 "type": "csv",
                 "metavar": "<argument names>",
-                "help": " List of valid magic values that `magic-value-compare` will not detect.",
+                "help": "List of valid magic values that `magic-value-compare` will not detect. "
+                "Supports integers, floats, negative numbers, for empty string enter ``''``,"
+                " for backslash values just use one backslash e.g \\n.",
             },
         ),
     )
 
+    def __init__(self, linter: PyLinter) -> None:
+        """Initialize checker instance."""
+        super().__init__(linter=linter)
+        self.valid_magic_vals: tuple[float | str, ...] = ()
+
+    def open(self) -> None:
+        # Extra manipulation is needed in case of using external configuration like an rcfile
+        if self._magic_vals_ext_configured():
+            self.valid_magic_vals = tuple(
+                self._parse_rcfile_magic_numbers(value)
+                for value in self.linter.config.valid_magic_values
+            )
+        else:
+            self.valid_magic_vals = self.linter.config.valid_magic_values
+
+    def _magic_vals_ext_configured(self) -> bool:
+        return not isinstance(self.linter.config.valid_magic_values, tuple)
+
     def _check_constants_comparison(self, node: nodes.Compare) -> None:
         """
         Magic values in any side of the comparison should be avoided,
@@ -74,11 +95,21 @@ class MagicValueChecker(BaseChecker):
                 confidence=HIGH,
             )
 
-    def _is_magic_value(self, node: nodes.NodeNG) -> bool:
+    def _is_magic_value(self, node: nodes.Const) -> bool:
         return (not utils.is_singleton_const(node)) and (
-            node.value not in self.linter.config.valid_magic_values
+            node.value not in (self.valid_magic_vals)
         )
 
+    @staticmethod
+    def _parse_rcfile_magic_numbers(parsed_val: str) -> float | str:
+        parsed_val = parsed_val.encode().decode("unicode_escape")
+
+        if parsed_val.startswith("'") and parsed_val.endswith("'"):
+            return parsed_val[1:-1]
+
+        is_number = regex_match(r"[-+]?\d+(\.0*)?$", parsed_val)
+        return float(parsed_val) if is_number else parsed_val
+
     @utils.only_required_for_messages("magic-comparison")
     def visit_compare(self, node: nodes.Compare) -> None:
         self._check_constants_comparison(node)