Add new check: unguarded-typing-import

Author: nickdrozd

pylint/checkers/variables.py

@@ -24,6 +24,7 @@
 from pylint.checkers.utils import (
     in_type_checking_block,
     is_module_ignored,
+    is_node_in_type_annotation_context,
     is_postponed_evaluation_enabled,
     is_sys_guard,
     overridden_method,
@@ -434,6 +435,14 @@ def _has_locals_call_after_node(stmt: nodes.NodeNG, scope: nodes.FunctionDef) ->
         "Used when an imported module or variable is not used from a "
         "`'from X import *'` style import.",
     ),
+    "R0615": (
+        "`%s` used only for typechecking but imported outside of a typechecking block",
+        "unguarded-typing-import",
+        "Used when an import is used only for typechecking but imported outside of a typechecking block.",
+        {
+            "default_enabled": False,
+        },
+    ),
     "W0621": (
         "Redefining name %r from outer scope (line %s)",
         "redefined-outer-name",
@@ -507,6 +516,7 @@ class NamesConsumer:
 
     to_consume: Consumption
     consumed: Consumption
+    consumed_as_type: Consumption
     consumed_uncertain: Consumption
     """Retrieves nodes filtered out by get_next_to_consume() that may not
     have executed.
@@ -523,6 +533,7 @@ def __init__(self, node: nodes.NodeNG, scope_type: str):
 
         self.to_consume = copy.copy(node.locals)
         self.consumed = {}
+        self.consumed_as_type = {}
         self.consumed_uncertain = defaultdict(list)
 
         self.names_under_always_false_test: set[str] = set()
@@ -531,30 +542,46 @@ def __init__(self, node: nodes.NodeNG, scope_type: str):
     def __repr__(self) -> str:
         _to_consumes = [f"{k}->{v}" for k, v in self.to_consume.items()]
         _consumed = [f"{k}->{v}" for k, v in self.consumed.items()]
+        _consumed_as_type = [f"{k}->{v}" for k, v in self.consumed_as_type.items()]
         _consumed_uncertain = [f"{k}->{v}" for k, v in self.consumed_uncertain.items()]
         to_consumes = ", ".join(_to_consumes)
         consumed = ", ".join(_consumed)
+        consumed_as_type = ", ".join(_consumed_as_type)
         consumed_uncertain = ", ".join(_consumed_uncertain)
         return f"""
 to_consume : {to_consumes}
 consumed : {consumed}
+consumed_as_type : {consumed_as_type}
 consumed_uncertain: {consumed_uncertain}
 scope_type : {self.scope_type}
 """
 
-    def mark_as_consumed(self, name: str, consumed_nodes: list[nodes.NodeNG]) -> None:
+    def mark_as_consumed(
+        self,
+        name: str,
+        consumed_nodes: list[nodes.NodeNG],
+        consumed_as_type: bool = False,
+    ) -> None:
         """Mark the given nodes as consumed for the name.
 
         If all of the nodes for the name were consumed, delete the name from
         the to_consume dictionary
         """
-        unconsumed = [n for n in self.to_consume[name] if n not in set(consumed_nodes)]
-        self.consumed[name] = consumed_nodes
+        consumed = self.consumed_as_type if consumed_as_type else self.consumed
+        consumed[name] = consumed_nodes
 
-        if unconsumed:
-            self.to_consume[name] = unconsumed
-        else:
-            del self.to_consume[name]
+        if name in self.to_consume:
+            unconsumed = [
+                n for n in self.to_consume[name] if n not in set(consumed_nodes)
+            ]
+
+            if unconsumed:
+                self.to_consume[name] = unconsumed
+            else:
+                del self.to_consume[name]
+
+        if not consumed_as_type and name in self.consumed_as_type:
+            del self.consumed_as_type[name]
 
     def get_next_to_consume(self, node: nodes.Name) -> list[nodes.NodeNG] | None:
         """Return a list of the nodes that define `node` from this scope.
@@ -594,6 +621,9 @@ def get_next_to_consume(self, node: nodes.Name) -> list[nodes.NodeNG] | None:
         if VariablesChecker._comprehension_between_frame_and_node(node):
             return found_nodes
 
+        if found_nodes is None:
+            found_nodes = self.consumed_as_type.get(name)
+
         # Filter out assignments in ExceptHandlers that node is not contained in
         if found_nodes:
             found_nodes = [
@@ -1386,7 +1416,8 @@ def leave_module(self, node: nodes.Module) -> None:
         assert len(self._to_consume) == 1
 
         self._check_metaclasses(node)
-        not_consumed = self._to_consume.pop().to_consume
+        consumer = self._to_consume.pop()
+        not_consumed = consumer.to_consume
         # attempt to check for __all__ if defined
         if "__all__" in node.locals:
             self._check_all(node, not_consumed)
@@ -1398,7 +1429,7 @@ def leave_module(self, node: nodes.Module) -> None:
         if not self.linter.config.init_import and node.package:
             return
 
-        self._check_imports(not_consumed)
+        self._check_imports(not_consumed, consumer.consumed_as_type)
         self._type_annotation_names = []
 
     def visit_classdef(self, node: nodes.ClassDef) -> None:
@@ -1702,7 +1733,11 @@ def _undefined_and_used_before_checker(
                 # They will have already had a chance to emit used-before-assignment.
                 # We check here instead of before every single return in _check_consumer()
                 nodes_to_consume += current_consumer.consumed_uncertain[node.name]
-                current_consumer.mark_as_consumed(node.name, nodes_to_consume)
+                current_consumer.mark_as_consumed(
+                    node.name,
+                    nodes_to_consume,
+                    consumed_as_type=is_node_in_type_annotation_context(node),
+                )
             if action is VariableVisitConsumerAction.CONTINUE:
                 continue
             if action is VariableVisitConsumerAction.RETURN:
@@ -3236,7 +3271,11 @@ def _check_globals(self, not_consumed: Consumption) -> None:
                 self.add_message("unused-variable", args=(name,), node=node)
 
     # pylint: disable = too-many-branches
-    def _check_imports(self, not_consumed: Consumption) -> None:
+    def _check_imports(
+        self,
+        not_consumed: Consumption,
+        consumed_as_type: Consumption,
+    ) -> None:
         local_names = _fix_dot_imports(not_consumed)
         checked = set()
         unused_wildcard_imports: defaultdict[
@@ -3324,8 +3363,26 @@ def _check_imports(self, not_consumed: Consumption) -> None:
             self.add_message(
                 "unused-wildcard-import", args=(arg_string, module[0]), node=module[1]
             )
+
+        self._check_type_imports(consumed_as_type)
+
         del self._to_consume
 
+    def _check_type_imports(
+        self,
+        consumed_as_type: dict[str, list[nodes.NodeNG]],
+    ) -> None:
+        for name, import_node in _fix_dot_imports(consumed_as_type):
+            if import_node.names[0][0] == "*":
+                continue
+
+            if not in_type_checking_block(import_node):
+                self.add_message(
+                    "unguarded-typing-import",
+                    args=name,
+                    node=import_node,
+                )
+
     def _check_metaclasses(self, node: nodes.Module | nodes.FunctionDef) -> None:
         """Update consumption analysis for metaclasses."""
         consumed: list[tuple[Consumption, str]] = []

tests/functional/u/unguarded_typing_import.py

@@ -0,0 +1,21 @@
+# pylint: disable = import-error, missing-module-docstring, missing-function-docstring, missing-class-docstring, too-few-public-methods,
+
+from mod import A  # [unguarded-typing-import]
+from mod import B
+
+def f(_: A):
+    pass
+
+def g(x: B):
+    assert isinstance(x, B)
+
+class C:
+    pass
+
+class D:
+    c: C
+
+    def h(self):
+        # --> BUG <--
+        # pylint: disable = undefined-variable
+        return [C() for _ in self.c]

tests/functional/u/unguarded_typing_import.rc

@@ -0,0 +1,2 @@
+[MESSAGES CONTROL]
+enable = unguarded-typing-import

tests/functional/u/unguarded_typing_import.txt

@@ -0,0 +1 @@
+unguarded-typing-import:3:0:3:17::`A` used only for typechecking but imported outside of a typechecking block:UNDEFINED