Fix astroid error for custom next method (#7622)

* short-circuit if next method doesnt have args
* check for builtins.next qname
* add inference confidence level

Author: clavedeluna

doc/whatsnew/fragments/7610.bugfix

@@ -0,0 +1,3 @@
+Fixes edge case of custom method named ``next`` raised an astroid error.
+
+Closes #7610

pylint/checkers/refactoring/refactoring_checker.py

@@ -979,7 +979,7 @@ def _check_stop_iteration_inside_generator(self, node: nodes.Raise) -> None:
         if not exc or not isinstance(exc, (bases.Instance, nodes.ClassDef)):
             return
         if self._check_exception_inherit_from_stopiteration(exc):
-            self.add_message("stop-iteration-return", node=node)
+            self.add_message("stop-iteration-return", node=node, confidence=INFERENCE)
 
     @staticmethod
     def _check_exception_inherit_from_stopiteration(
@@ -1135,7 +1135,11 @@ def _looks_like_infinite_iterator(param: nodes.NodeNG) -> bool:
             return
 
         inferred = utils.safe_infer(node.func)
-        if getattr(inferred, "name", "") == "next":
+
+        if (
+            isinstance(inferred, nodes.FunctionDef)
+            and inferred.qname() == "builtins.next"
+        ):
             frame = node.frame(future=True)
             # The next builtin can only have up to two
             # positional arguments and no keyword arguments
@@ -1147,7 +1151,9 @@ def _looks_like_infinite_iterator(param: nodes.NodeNG) -> bool:
                 and not utils.node_ignores_exception(node, StopIteration)
                 and not _looks_like_infinite_iterator(node.args[0])
             ):
-                self.add_message("stop-iteration-return", node=node)
+                self.add_message(
+                    "stop-iteration-return", node=node, confidence=INFERENCE
+                )
 
     def _check_nested_blocks(
         self,

tests/functional/s/stop_iteration_inside_generator.py

@@ -4,17 +4,20 @@
 # pylint: disable=missing-docstring,invalid-name,import-error, try-except-raise, wrong-import-position,not-callable,raise-missing-from
 import asyncio
 
+
 class RebornStopIteration(StopIteration):
     """
     A class inheriting from StopIteration exception
     """
 
+
 # This one is ok
 def gen_ok():
     yield 1
     yield 2
     yield 3
 
+
 # pylint should warn about this one
 # because of a direct raising of StopIteration inside generator
 def gen_stopiter():
@@ -23,6 +26,7 @@ def gen_stopiter():
     yield 3
     raise StopIteration  # [stop-iteration-return]
 
+
 # pylint should warn about this one
 # because of a direct raising of an exception inheriting from StopIteration inside generator
 def gen_stopiterchild():
@@ -31,13 +35,15 @@ def gen_stopiterchild():
     yield 3
     raise RebornStopIteration  # [stop-iteration-return]
 
+
 # pylint should warn here
 # because of the possibility that next raises a StopIteration exception
 def gen_next_raises_stopiter():
     g = gen_ok()
     while True:
         yield next(g)  # [stop-iteration-return]
 
+
 # This one is the same as gen_next_raises_stopiter
 # but is ok because the next function is inside
 # a try/except block handling StopIteration
@@ -49,6 +55,7 @@ def gen_next_inside_try_except():
         except StopIteration:
             return
 
+
 # This one is the same as gen_next_inside_try_except
 # but is not ok because the next function is inside
 # a try/except block that don't handle StopIteration
@@ -60,6 +67,7 @@ def gen_next_inside_wrong_try_except():
         except ValueError:
             return
 
+
 # This one is the same as gen_next_inside_try_except
 # but is not ok because the next function is inside
 # a try/except block that handle StopIteration but reraise it
@@ -71,11 +79,13 @@ def gen_next_inside_wrong_try_except2():
         except StopIteration:
             raise StopIteration  # [stop-iteration-return]
 
+
 # Those two last are ok
 def gen_in_for():
     for el in gen_ok():
         yield el
 
+
 def gen_yield_from():
     yield from gen_ok()
 
@@ -84,7 +94,7 @@ def gen_dont_crash_on_no_exception():
     g = gen_ok()
     while True:
         try:
-            yield next(g) # [stop-iteration-return]
+            yield next(g)  # [stop-iteration-return]
         except ValueError:
             raise
 
@@ -97,7 +107,7 @@ def gen_dont_crash_on_uninferable():
 
 # https://github.com/PyCQA/pylint/issues/1830
 def gen_next_with_sentinel():
-    yield next([], 42) # No bad return
+    yield next([], 42)  # No bad return
 
 
 from itertools import count
@@ -113,6 +123,7 @@ def generator_using_next():
 class SomeClassWithNext:
     def next(self):
         return iter([1, 2, 3])
+
     def some_gen(self):
         for value in self.next():
             yield value
@@ -122,8 +133,39 @@ def some_gen(self):
 
 
 def something_invalid():
-    raise Exception('cannot iterate this')
+    raise Exception("cannot iterate this")
 
 
 def invalid_object_passed_to_next():
-    yield next(something_invalid()) # [stop-iteration-return]
+    yield next(something_invalid())  # [stop-iteration-return]
+
+
+# pylint: disable=redefined-builtin,too-many-function-args
+def safeiter(it):
+    """Regression test for issue #7610 when ``next`` builtin is redefined"""
+
+    def next():
+        while True:
+            try:
+                return next(it)
+            except StopIteration:
+                raise
+
+    it = iter(it)
+    while True:
+        yield next()
+
+def other_safeiter(it):
+    """Regression test for issue #7610 when ``next`` builtin is redefined"""
+
+    def next(*things):
+        print(*things)
+        while True:
+            try:
+                return next(it)
+            except StopIteration:
+                raise
+
+    it = iter(it)
+    while True:
+        yield next(1, 2)

tests/functional/s/stop_iteration_inside_generator.txt

@@ -1,7 +1,7 @@
-stop-iteration-return:24:4:24:23:gen_stopiter:Do not raise StopIteration in generator, use return statement instead:UNDEFINED
-stop-iteration-return:32:4:32:29:gen_stopiterchild:Do not raise StopIteration in generator, use return statement instead:UNDEFINED
-stop-iteration-return:39:14:39:21:gen_next_raises_stopiter:Do not raise StopIteration in generator, use return statement instead:UNDEFINED
-stop-iteration-return:59:18:59:25:gen_next_inside_wrong_try_except:Do not raise StopIteration in generator, use return statement instead:UNDEFINED
-stop-iteration-return:72:12:72:31:gen_next_inside_wrong_try_except2:Do not raise StopIteration in generator, use return statement instead:UNDEFINED
-stop-iteration-return:87:18:87:25:gen_dont_crash_on_no_exception:Do not raise StopIteration in generator, use return statement instead:UNDEFINED
-stop-iteration-return:129:10:129:35:invalid_object_passed_to_next:Do not raise StopIteration in generator, use return statement instead:UNDEFINED
+stop-iteration-return:27:4:27:23:gen_stopiter:Do not raise StopIteration in generator, use return statement instead:INFERENCE
+stop-iteration-return:36:4:36:29:gen_stopiterchild:Do not raise StopIteration in generator, use return statement instead:INFERENCE
+stop-iteration-return:44:14:44:21:gen_next_raises_stopiter:Do not raise StopIteration in generator, use return statement instead:INFERENCE
+stop-iteration-return:66:18:66:25:gen_next_inside_wrong_try_except:Do not raise StopIteration in generator, use return statement instead:INFERENCE
+stop-iteration-return:80:12:80:31:gen_next_inside_wrong_try_except2:Do not raise StopIteration in generator, use return statement instead:INFERENCE
+stop-iteration-return:97:18:97:25:gen_dont_crash_on_no_exception:Do not raise StopIteration in generator, use return statement instead:INFERENCE
+stop-iteration-return:140:10:140:35:invalid_object_passed_to_next:Do not raise StopIteration in generator, use return statement instead:INFERENCE