Add broken NoReturn check (#5304)

ChangeLog

@@ -400,6 +400,12 @@ Release date: TBA
 
   Closes #5371
 
+* ``TypingChecker``
+
+  * Added new check ``broken-noreturn`` to detect broken uses of ``typing.NoReturn``
+    if ``py-version`` is set to Python ``3.7.1`` or below.
+    https://bugs.python.org/issue34921
+
 * The ``testutils`` for unittests now accept ``end_lineno`` and ``end_column``. Tests
   without these will trigger a ``DeprecationWarning``.
 
@@ -555,6 +561,7 @@ Release date: 2021-11-24
 * Properly identify parameters with no documentation and add new message called ``missing-any-param-doc``
 
   Closes #3799
+
 * Add checkers ``overridden-final-method`` & ``subclassed-final-class``
 
   Closes #3197

doc/whatsnew/2.13.rst

@@ -75,6 +75,12 @@ Extensions
 
 * Pyreverse - add output in mermaid-js format and html which is an mermaid js diagram with html boilerplate
 
+* ``TypingChecker``
+
+  * Added new check ``broken-noreturn`` to detect broken uses of ``typing.NoReturn``
+    if ``py-version`` is set to Python ``3.7.1`` or below.
+    https://bugs.python.org/issue34921
+
 * ``DocstringParameterChecker``
 
   * Fixed incorrect classification of Numpy-style docstring as Google-style docstring for

pylint/extensions/typing.py

@@ -7,9 +7,10 @@
 from pylint.checkers.utils import (
     check_messages,
     is_node_in_type_annotation_context,
+    is_postponed_evaluation_enabled,
     safe_infer,
 )
-from pylint.interfaces import IAstroidChecker
+from pylint.interfaces import INFERENCE, IAstroidChecker
 from pylint.utils.utils import get_global_option
 
 if TYPE_CHECKING:
@@ -68,6 +69,12 @@ class TypingAlias(NamedTuple):
 
 ALIAS_NAMES = frozenset(key.split(".")[1] for key in DEPRECATED_TYPING_ALIASES)
 UNION_NAMES = ("Optional", "Union")
+TYPING_NORETURN = frozenset(
+    (
+        "typing.NoReturn",
+        "typing_extensions.NoReturn",
+    )
+)
 
 
 class DeprecatedTypingAliasMsg(NamedTuple):
@@ -103,6 +110,14 @@ class TypingChecker(BaseChecker):
             "Emitted when 'typing.Union' or 'typing.Optional' is used "
             "instead of the alternative Union syntax 'int | None'.",
         ),
+        "E6004": (
+            "'NoReturn' inside compound types is broken in 3.7.0 / 3.7.1",
+            "broken-noreturn",
+            "``typing.NoReturn`` inside compound types is broken in "
+            "Python 3.7.0 and 3.7.1. If not dependent on runtime introspection, "
+            "use string annotation instead. E.g. "
+            "``Callable[..., 'NoReturn']``. https://bugs.python.org/issue34921",
+        ),
     }
     options = (
         (
@@ -153,6 +168,8 @@ def open(self) -> None:
             self._py37_plus and self.config.runtime_typing is False
         )
 
+        self._should_check_noreturn = py_version < (3, 7, 2)
+
     def _msg_postponed_eval_hint(self, node) -> str:
         """Message hint if postponed evaluation isn't enabled."""
         if self._py310_plus or "annotations" in node.root().future_imports:
@@ -163,23 +180,29 @@ def _msg_postponed_eval_hint(self, node) -> str:
         "deprecated-typing-alias",
         "consider-using-alias",
         "consider-alternative-union-syntax",
+        "broken-noreturn",
     )
     def visit_name(self, node: nodes.Name) -> None:
         if self._should_check_typing_alias and node.name in ALIAS_NAMES:
             self._check_for_typing_alias(node)
         if self._should_check_alternative_union_syntax and node.name in UNION_NAMES:
             self._check_for_alternative_union_syntax(node, node.name)
+        if self._should_check_noreturn and node.name == "NoReturn":
+            self._check_broken_noreturn(node)
 
     @check_messages(
         "deprecated-typing-alias",
         "consider-using-alias",
         "consider-alternative-union-syntax",
+        "broken-noreturn",
     )
     def visit_attribute(self, node: nodes.Attribute) -> None:
         if self._should_check_typing_alias and node.attrname in ALIAS_NAMES:
             self._check_for_typing_alias(node)
         if self._should_check_alternative_union_syntax and node.attrname in UNION_NAMES:
             self._check_for_alternative_union_syntax(node, node.attrname)
+        if self._should_check_noreturn and node.attrname == "NoReturn":
+            self._check_broken_noreturn(node)
 
     def _check_for_alternative_union_syntax(
         self,
@@ -279,6 +302,32 @@ def leave_module(self, node: nodes.Module) -> None:
         self._alias_name_collisions.clear()
         self._consider_using_alias_msgs.clear()
 
+    def _check_broken_noreturn(self, node: Union[nodes.Name, nodes.Attribute]) -> None:
+        """Check for 'NoReturn' inside compound types."""
+        if not isinstance(node.parent, nodes.BaseContainer):
+            # NoReturn not part of a Union or Callable type
+            return
+
+        if is_postponed_evaluation_enabled(node) and is_node_in_type_annotation_context(
+            node
+        ):
+            return
+
+        for inferred in node.infer():
+            # To deal with typing_extensions, don't use safe_infer
+            if (
+                isinstance(inferred, (nodes.FunctionDef, nodes.ClassDef))
+                and inferred.qname() in TYPING_NORETURN
+                # In Python 3.6, NoReturn is alias of '_NoReturn'
+                # In Python 3.7 - 3.8, NoReturn is alias of '_SpecialForm'
+                or isinstance(inferred, astroid.bases.BaseInstance)
+                and isinstance(inferred._proxied, nodes.ClassDef)
+                and inferred._proxied.qname()
+                in {"typing._NoReturn", "typing._SpecialForm"}
+            ):
+                self.add_message("broken-noreturn", node=node, confidence=INFERENCE)
+                break
+
 
 def register(linter: "PyLinter") -> None:
     linter.register_checker(TypingChecker(linter))

requirements_test_min.txt

@@ -1,5 +1,6 @@
 -e .[testutil]
 # astroid dependency is also defined in setup.cfg
 astroid==2.9.3  # Pinned to a specific version for tests
+typing-extensions~=4.0
 pytest~=7.0
 pytest-benchmark~=3.4

tests/functional/ext/typing/typing_broken_noreturn.py

@@ -0,0 +1,32 @@
+"""
+'typing.NoReturn' is broken inside compond types for Python 3.7.0
+https://bugs.python.org/issue34921
+
+If no runtime introspection is required, use string annotations instead.
+"""
+# pylint: disable=missing-docstring
+import typing
+from typing import Callable, NoReturn, Union
+
+import typing_extensions
+
+
+def func1() -> NoReturn:
+    raise Exception
+
+def func2() -> Union[None, NoReturn]:  # [broken-noreturn]
+    pass
+
+def func3() -> Union[None, "NoReturn"]:
+    pass
+
+def func4() -> Union[None, typing.NoReturn]:  # [broken-noreturn]
+    pass
+
+def func5() -> Union[None, typing_extensions.NoReturn]:  # [broken-noreturn]
+    pass
+
+
+Alias1 = NoReturn
+Alias2 = Callable[..., NoReturn]  # [broken-noreturn]
+Alias3 = Callable[..., "NoReturn"]

tests/functional/ext/typing/typing_broken_noreturn.rc

@@ -0,0 +1,3 @@
+[master]
+py-version=3.7
+load-plugins=pylint.extensions.typing

tests/functional/ext/typing/typing_broken_noreturn.txt

@@ -0,0 +1,4 @@
+broken-noreturn:17:27:17:35:func2:'NoReturn' inside compound types is broken in 3.7.0 / 3.7.1:INFERENCE
+broken-noreturn:23:27:23:42:func4:'NoReturn' inside compound types is broken in 3.7.0 / 3.7.1:INFERENCE
+broken-noreturn:26:27:26:53:func5:'NoReturn' inside compound types is broken in 3.7.0 / 3.7.1:INFERENCE
+broken-noreturn:31:23:31:31::'NoReturn' inside compound types is broken in 3.7.0 / 3.7.1:INFERENCE

tests/functional/ext/typing/typing_broken_noreturn_future_import.py

@@ -0,0 +1,37 @@
+"""
+'typing.NoReturn' is broken inside compond types for Python 3.7.0
+https://bugs.python.org/issue34921
+
+If no runtime introspection is required, use string annotations instead.
+
+With 'from __future__ import annotations', only emit errors for nodes
+not in a type annotation context.
+"""
+# pylint: disable=missing-docstring
+from __future__ import annotations
+
+import typing
+from typing import Callable, NoReturn, Union
+
+import typing_extensions
+
+
+def func1() -> NoReturn:
+    raise Exception
+
+def func2() -> Union[None, NoReturn]:
+    pass
+
+def func3() -> Union[None, "NoReturn"]:
+    pass
+
+def func4() -> Union[None, typing.NoReturn]:
+    pass
+
+def func5() -> Union[None, typing_extensions.NoReturn]:
+    pass
+
+
+Alias1 = NoReturn
+Alias2 = Callable[..., NoReturn]  # [broken-noreturn]
+Alias3 = Callable[..., "NoReturn"]

tests/functional/ext/typing/typing_broken_noreturn_future_import.rc

@@ -0,0 +1,6 @@
+[master]
+py-version=3.7
+load-plugins=pylint.extensions.typing
+
+[testoptions]
+min_pyver=3.7

tests/functional/ext/typing/typing_broken_noreturn_future_import.txt

@@ -0,0 +1 @@
+broken-noreturn:36:23:36:31::'NoReturn' inside compound types is broken in 3.7.0 / 3.7.1:INFERENCE

tests/functional/ext/typing/typing_broken_noreturn_py372.py

@@ -0,0 +1,34 @@
+"""
+'typing.NoReturn' is broken inside compond types for Python 3.7.0
+https://bugs.python.org/issue34921
+
+If no runtime introspection is required, use string annotations instead.
+
+Don't emit errors if py-version set to >= 3.7.2.
+"""
+# pylint: disable=missing-docstring
+import typing
+from typing import Callable, NoReturn, Union
+
+import typing_extensions
+
+
+def func1() -> NoReturn:
+    raise Exception
+
+def func2() -> Union[None, NoReturn]:
+    pass
+
+def func3() -> Union[None, "NoReturn"]:
+    pass
+
+def func4() -> Union[None, typing.NoReturn]:
+    pass
+
+def func5() -> Union[None, typing_extensions.NoReturn]:
+    pass
+
+
+Alias1 = NoReturn
+Alias2 = Callable[..., NoReturn]
+Alias3 = Callable[..., "NoReturn"]

tests/functional/ext/typing/typing_broken_noreturn_py372.rc

@@ -0,0 +1,3 @@
+[master]
+py-version=3.7.2
+load-plugins=pylint.extensions.typing