Add check to make sure only strings are assigned to __name__ (#3271)

Close #583

CONTRIBUTORS.txt

@@ -356,3 +356,5 @@ contributors:
 * Craig Henriques: contributor
 
 * Matthijs Blom: contributor
+
+* Andy Palmer: contributor

ChangeLog

@@ -7,6 +7,10 @@ What's New in Pylint 2.5.0?
 
 Release date: TBA
 
+* Add a check for non string assignment to __name__ attribute.
+
+  Close #583
+
 * `__pow__`, `__imatmul__`, `__trunc__`, `__floor__`, and `__ceil__` are recognized as special method names.
 
   Close #3281

doc/whatsnew/2.5.rst

@@ -66,3 +66,5 @@ separated list of regexes, that if a name matches will be always marked as a bla
 * Mutable ``collections.*`` are now flagged as dangerous defaults.
 
 * Add new --fail-under flag for setting the threshold for the score to fail overall tests. If the score is over the fail-under threshold, pylint will complete SystemExit with value 0 to indicate no errors.
+
+* Add a new check (non-str-assignment-to-dunder-name) to ensure that only strings are assigned to ``__name__`` attributes

pylint/checkers/typecheck.py

@@ -27,6 +27,7 @@
 # Copyright (c) 2018 Konstantin <Github@pheanex.de>
 # Copyright (c) 2018 Justin Li <justinnhli@users.noreply.github.com>
 # Copyright (c) 2018 Bryce Guinta <bryce.paul.guinta@gmail.com>
+# Copyright (c) 2019 Andy Palmer <contactninezerozeronine@gmail.com>
 
 # Licensed under the GPL: https://www.gnu.org/licenses/old-licenses/gpl-2.0.html
 # For details: https://github.com/PyCQA/pylint/blob/master/COPYING
@@ -389,6 +390,11 @@ def _missing_member_hint(owner, attrname, distance_threshold, max_choices):
         "Emitted  when the caller's argument names fully match the parameter "
         "names in the function signature but do not have the same order.",
     ),
+    "W1115": (
+        "Non-string value assigned to __name__",
+        "non-str-assignment-to-dunder-name",
+        "Emitted when a non-string vaue is assigned to __name__",
+    ),
 }
 
 # builtin sequence types in Python 2 and 3.
@@ -986,8 +992,20 @@ def _get_nomember_msgid_hint(self, node, owner):
                 hint = ""
         return msg, hint
 
-    @check_messages("assignment-from-no-return", "assignment-from-none")
+    @check_messages(
+        "assignment-from-no-return",
+        "assignment-from-none",
+        "non-str-assignment-to-dunder-name",
+    )
     def visit_assign(self, node):
+        """
+        Process assignments in the AST.
+        """
+
+        self._check_assignment_from_function_call(node)
+        self._check_dundername_is_string(node)
+
+    def _check_assignment_from_function_call(self, node):
         """check that if assigning to a function call, the function is
         possibly returning something valuable
         """
@@ -1035,6 +1053,31 @@ def visit_assign(self, node):
             else:
                 self.add_message("assignment-from-none", node=node)
 
+    def _check_dundername_is_string(self, node):
+        """
+        Check a string is assigned to self.__name__
+        """
+
+        # Check the left hand side of the assignment is <something>.__name__
+        lhs = node.targets[0]
+        if not isinstance(lhs, astroid.node_classes.AssignAttr):
+            return
+        if not lhs.attrname == "__name__":
+            return
+
+        # If the right hand side is not a string
+        rhs = node.value
+        if isinstance(rhs, astroid.Const) and isinstance(rhs.value, str):
+            return
+        inferred = utils.safe_infer(rhs)
+        if not inferred:
+            return
+        if not (
+            isinstance(inferred, astroid.Const) and isinstance(inferred.value, str)
+        ):
+            # Add the message
+            self.add_message("non-str-assignment-to-dunder-name", node=node)
+
     def _check_uninferable_call(self, node):
         """
         Check that the given uninferable Call node does not

tests/functional/n/non_str_assignment_to_dunder_name.py

@@ -0,0 +1,53 @@
+# pylint: disable=missing-module-docstring, missing-class-docstring
+# pylint: disable=too-few-public-methods, missing-function-docstring
+# pylint: disable=import-error
+
+import random
+
+from unknown import Unknown
+
+
+class ExampleClass():
+    pass
+
+
+def example_function():
+    pass
+
+
+def returns_str():
+    return "abcd"
+
+
+def returns_int():
+    return 0
+
+
+def returns_tuple():
+    return 0, "abc"
+
+
+# Might not be thorough if same hash seed is used in testing...
+def returns_random_type():
+    if random.randint(0, 1) > 0:
+        return 0
+
+    return "abc"
+
+ExampleClass.__name__ = 1  # [non-str-assignment-to-dunder-name]
+ExampleClass.__name__ = True  # [non-str-assignment-to-dunder-name]
+ExampleClass.__name__ = returns_tuple() # [non-str-assignment-to-dunder-name]
+ExampleClass.__name__ = returns_int() # [non-str-assignment-to-dunder-name]
+ExampleClass.__name__ = "foo"
+ExampleClass.__name__ = returns_str()
+ExampleClass.__name__ = returns_random_type()
+ExampleClass.__name__ = Unknown
+
+example_function.__name__ = 1  # [non-str-assignment-to-dunder-name]
+example_function.__name__ = True  # [non-str-assignment-to-dunder-name]
+example_function.__name__ = returns_tuple() # [non-str-assignment-to-dunder-name]
+example_function.__name__ = returns_int() # [non-str-assignment-to-dunder-name]
+example_function.__name__ = "foo"
+example_function.__name__ = returns_str()
+example_function.__name__ = returns_random_type()
+example_function.__name__ = Unknown

tests/functional/n/non_str_assignment_to_dunder_name.txt

@@ -0,0 +1,8 @@
+non-str-assignment-to-dunder-name:37::Non-string value assigned to __name__
+non-str-assignment-to-dunder-name:38::Non-string value assigned to __name__
+non-str-assignment-to-dunder-name:39::Non-string value assigned to __name__
+non-str-assignment-to-dunder-name:40::Non-string value assigned to __name__
+non-str-assignment-to-dunder-name:46::Non-string value assigned to __name__
+non-str-assignment-to-dunder-name:47::Non-string value assigned to __name__
+non-str-assignment-to-dunder-name:48::Non-string value assigned to __name__
+non-str-assignment-to-dunder-name:49::Non-string value assigned to __name__