Fix reconstruction of nodes for FormattedValue. Close pylint-dev/pylint#1582

Author: PCManticore

astroid/brain/brain_fstrings.py

@@ -27,7 +27,7 @@ def _clone_node_with_lineno(node, parent, lineno):
             for param in other_fields
         })
     new_node = cls(**init_params)
-    if hasattr(node, 'postinit'):
+    if hasattr(node, 'postinit') and _astroid_fields:
         new_node.postinit(**postinit_params)
     return new_node
 
@@ -58,4 +58,3 @@ def _transform_formatted_value(node):
     astroid.MANAGER.register_transform(
         astroid.FormattedValue,
         _transform_formatted_value)
-

astroid/tests/unittest_brain.py

@@ -768,5 +768,21 @@ def test_regex_flags(self):
             self.assertEqual(next(re_ast[name].infer()).value, getattr(re, name))
 
 
+class BrainFStrings(unittest.TestCase):
+
+    def test_no_crash_on_const_reconstruction(self):
+        node = builder.extract_node('''
+        max_width = 10
+
+        test1 = f'{" ":{max_width+4}}'
+        print(f'"{test1}"')
+
+        test2 = f'[{"7":>{max_width}}:0]'
+        test2
+        ''')
+        inferred = next(node.infer())
+        self.assertIs(inferred, util.Uninferable)
+
+
 if __name__ == '__main__':
     unittest.main()