Fix a crash for Enum class decorated with dataclass (#9104) (#9112)

* Fix a crash when an enum class which is also decorated with a ``dataclasses.dataclass`` decorator is defined.

Closes #9100

* Update test to mention the `astroid` issue that addresses the missing ``__members__`` object.

* Use an `if` instead of the `try/except` block.

* Update pylint/checkers/utils.py

Co-authored-by: Daniël van Noord <[email protected]>

---------

Co-authored-by: Daniël van Noord <[email protected]>
(cherry picked from commit 2c3425d)

Co-authored-by: Mark Byrne <[email protected]>
Co-authored-by: Pierre Sassoulas <[email protected]>

Author: 3 people

doc/whatsnew/fragments/9100.other

@@ -0,0 +1,3 @@
+Fix a crash when an enum class which is also decorated with a ``dataclasses.dataclass`` decorator is defined.
+
+Closes #9100

pylint/checkers/utils.py

@@ -2281,5 +2281,8 @@ def is_enum_member(node: nodes.AssignName) -> bool:
     ):
         return False
 
-    enum_member_objects = frame.locals.get("__members__")[0].items
-    return node.name in [name_obj.name for value, name_obj in enum_member_objects]
+    members = frame.locals.get("__members__")
+    # A dataclass is one known case for when `members` can be `None`
+    if members is None:
+        return False
+    return node.name in [name_obj.name for value, name_obj in members[0].items]

tests/functional/i/invalid/invalid_name/invalid_name_enum.py

@@ -2,6 +2,7 @@
 # pylint: disable=too-few-public-methods
 
 
+from dataclasses import dataclass
 from enum import Enum
 
 
@@ -28,3 +29,11 @@ def __init__(self, red: int, green: int, blue: int) -> None:
     def as_hex(self) -> str:
         """Get hex 'abcdef' representation for a color."""
         return f'{self.red:0{2}x}{self.green:0{2}x}{self.blue:0{2}x}'
+
+
+@dataclass
+class Something(str, Enum):
+    """ A false positive for ``invalid-name``
+    which should be fixed by https://github.com/pylint-dev/astroid/issues/2317
+    """
+    ASD: str = 1  # [invalid-name]

tests/functional/i/invalid/invalid_name/invalid_name_enum.txt

@@ -1 +1,2 @@
-invalid-name:16:4:16:14:Color:"Class constant name ""aquamarine"" doesn't conform to UPPER_CASE naming style":HIGH
+invalid-name:17:4:17:14:Color:"Class constant name ""aquamarine"" doesn't conform to UPPER_CASE naming style":HIGH
+invalid-name:39:4:None:None:Something:"Attribute name ""ASD"" doesn't conform to snake_case naming style":HIGH