Fix false positive unused-variable for globals matching dummy-variables-rgx

When `allow-global-unused-variables` is disabled, global variables whose
names match `dummy-variables-rgx` were still reported as unused (W0612).
This adds a check for the dummy variable regex in `_check_globals`,
consistent with how local variables are already handled.

Closes #10890

Co-Authored-By: Claude Opus 4.6 <[email protected]>

Author: 2 people

doc/whatsnew/fragments/10890.false_positive

@@ -0,0 +1,5 @@
+Fix a false positive for ``unused-variable`` where global variables matching
+``dummy-variables-rgx`` were still reported as unused when
+``allow-global-unused-variables`` was disabled.
+
+Closes #10890

pylint/checkers/variables.py

@@ -3286,6 +3286,8 @@ def _check_globals(self, not_consumed: Consumption) -> None:
                     and node.modname == "__future__"
                 ):
                     continue
+                if self._is_name_ignored(node, name):
+                    continue
                 self.add_message("unused-variable", args=(name,), node=node)
 
     # pylint: disable = too-many-branches

tests/functional/u/unused/unused_global_variable5.py

@@ -0,0 +1,9 @@
+# pylint: disable=missing-docstring,invalid-name
+
+# Test that global variables matching dummy-variables-rgx are not
+# reported as unused (issue #10890).
+
+_ = []  # This should NOT trigger unused-variable
+__ = {}  # This should NOT trigger unused-variable
+
+var = "pylint"  # [unused-variable]

tests/functional/u/unused/unused_global_variable5.rc

@@ -0,0 +1,3 @@
+[variables]
+allow-global-unused-variables=no
+dummy-variables-rgx=_+$

tests/functional/u/unused/unused_global_variable5.txt

@@ -0,0 +1 @@
+unused-variable:9:0:9:3::Unused variable 'var':UNDEFINED