Add __main__ as inferred value for __name__ (#2345)

ChangeLog

@@ -12,6 +12,11 @@ Release date: TBA
 
   Refs pylint-dev/pylint#9193
 
+* Add ``__main__`` as a possible inferred value for ``__name__`` to improve
+  control flow inference around ``if __name__ == "__main__":`` guards.
+
+  Closes #2071
+
 
 What's New in astroid 3.0.3?
 ============================

astroid/nodes/scoped_nodes/scoped_nodes.py

@@ -41,7 +41,15 @@
 from astroid.interpreter.dunder_lookup import lookup
 from astroid.interpreter.objectmodel import ClassModel, FunctionModel, ModuleModel
 from astroid.manager import AstroidManager
-from astroid.nodes import Arguments, Const, NodeNG, Unknown, _base_nodes, node_classes
+from astroid.nodes import (
+    Arguments,
+    Const,
+    NodeNG,
+    Unknown,
+    _base_nodes,
+    const_factory,
+    node_classes,
+)
 from astroid.nodes.scoped_nodes.mixin import ComprehensionScope, LocalsDictNodeNG
 from astroid.nodes.scoped_nodes.utils import builtin_lookup
 from astroid.nodes.utils import Position
@@ -346,6 +354,8 @@ def getattr(
 
         if name in self.special_attributes and not ignore_locals and not name_in_locals:
             result = [self.special_attributes.lookup(name)]
+            if name == "__name__":
+                result.append(const_factory("__main__"))
         elif not ignore_locals and name_in_locals:
             result = self.locals[name]
         elif self.package:

tests/test_scoped_nodes.py

@@ -79,9 +79,11 @@ def setUp(self) -> None:
 
 class ModuleNodeTest(ModuleLoader, unittest.TestCase):
     def test_special_attributes(self) -> None:
-        self.assertEqual(len(self.module.getattr("__name__")), 1)
+        self.assertEqual(len(self.module.getattr("__name__")), 2)
         self.assertIsInstance(self.module.getattr("__name__")[0], nodes.Const)
         self.assertEqual(self.module.getattr("__name__")[0].value, "data.module")
+        self.assertIsInstance(self.module.getattr("__name__")[1], nodes.Const)
+        self.assertEqual(self.module.getattr("__name__")[1].value, "__main__")
         self.assertEqual(len(self.module.getattr("__doc__")), 1)
         self.assertIsInstance(self.module.getattr("__doc__")[0], nodes.Const)
         self.assertEqual(