pylint runtime error (StopIteration) due to _inference_tip_cached KeyError

[cj-matti-niemenmaa]

Steps to reproduce

Run pylint on a file containing the following (I called it asdf.py but I doubt it matters):

def get_list():
    return [1] if True else [2]

def find_int():
    return int(get_list()[0])

def foo():
    if True:
        return find_int()
    else:
        return find_int()

x = foo()
assert x / x > 0

(This is obviously a heavily reduced case based on the actual code...)

Current behavior

************* Module asdf
/asdf.py:1:0: C0111: Missing module docstring (missing-docstring)
/asdf.py:1:0: C0111: Missing function docstring (missing-docstring)
/asdf.py:2:11: W0125: Using a conditional statement with a constant value (using-constant-test)
/asdf.py:4:0: C0111: Missing function docstring (missing-docstring)
/asdf.py:7:0: C0102: Black listed name "foo" (blacklisted-name)
/asdf.py:7:0: C0111: Missing function docstring (missing-docstring)
/asdf.py:8:4: R1705: Unnecessary "else" after "return" (no-else-return)
/asdf.py:8:4: W0125: Using a conditional statement with a constant value (using-constant-test)
Traceback (most recent call last):
  File "/usr/local/lib/python3.7/site-packages/astroid/__init__.py", line 91, in _inference_tip_cached
    return iter(_cache[func, node])
KeyError: (<function register_builtin_transform.<locals>._transform_wrapper at 0x7f672229eae8>, <Call l.5 at 0x7f67218e5d68>)

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/local/lib/python3.7/site-packages/astroid/scoped_nodes.py", line 1666, in infer_call_result
    yield from returnnode.value.infer(context)
  File "/usr/local/lib/python3.7/site-packages/astroid/node_classes.py", line 352, in infer
    return self._explicit_inference(self, context, **kwargs)
  File "/usr/local/lib/python3.7/site-packages/astroid/__init__.py", line 93, in _inference_tip_cached
    result = func(*args, **kwargs)
  File "/usr/local/lib/python3.7/site-packages/astroid/brain/brain_builtin_inference.py", line 129, in _transform_wrapper
    result = transform(node, context=context)
  File "/usr/local/lib/python3.7/site-packages/astroid/brain/brain_builtin_inference.py", line 716, in infer_int
    first_value = next(call.positional_arguments[0].infer(context=context))
StopIteration

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/usr/local/bin/pylint", line 11, in <module>
    sys.exit(run_pylint())
  File "/usr/local/lib/python3.7/site-packages/pylint/__init__.py", line 20, in run_pylint
    Run(sys.argv[1:])
  File "/usr/local/lib/python3.7/site-packages/pylint/lint.py", line 1696, in __init__
    linter.check(args)
  File "/usr/local/lib/python3.7/site-packages/pylint/lint.py", line 983, in check
    self._do_check(files_or_modules)
  File "/usr/local/lib/python3.7/site-packages/pylint/lint.py", line 1143, in _do_check
    self.check_astroid_module(ast_node, walker, rawcheckers, tokencheckers)
  File "/usr/local/lib/python3.7/site-packages/pylint/lint.py", line 1227, in check_astroid_module
    walker.walk(ast_node)
  File "/usr/local/lib/python3.7/site-packages/pylint/utils/ast_walker.py", line 77, in walk
    self.walk(child)
  File "/usr/local/lib/python3.7/site-packages/pylint/utils/ast_walker.py", line 77, in walk
    self.walk(child)
  File "/usr/local/lib/python3.7/site-packages/pylint/utils/ast_walker.py", line 74, in walk
    callback(astroid)
  File "/usr/local/lib/python3.7/site-packages/pylint/checkers/base.py", line 1779, in visit_assignname
    if isinstance(utils.safe_infer(assign_type.value), astroid.ClassDef):
  File "/usr/local/lib/python3.7/site-packages/pylint/checkers/utils.py", line 1087, in safe_infer
    next(inferit)
  File "/usr/local/lib/python3.7/site-packages/astroid/decorators.py", line 141, in raise_if_nothing_inferred
    yield from generator
  File "/usr/local/lib/python3.7/site-packages/astroid/decorators.py", line 95, in wrapped
    res = next(generator)
  File "/usr/local/lib/python3.7/site-packages/astroid/inference.py", line 219, in infer_call
    yield from callee.infer_call_result(caller=self, context=callcontext)
  File "/usr/local/lib/python3.7/site-packages/astroid/scoped_nodes.py", line 1666, in infer_call_result
    yield from returnnode.value.infer(context)
  File "/usr/local/lib/python3.7/site-packages/astroid/util.py", line 160, in limit_inference
    yield from islice(iterator, size)
  File "/usr/local/lib/python3.7/site-packages/astroid/context.py", line 113, in cache_generator
    for result in generator:
  File "/usr/local/lib/python3.7/site-packages/astroid/decorators.py", line 131, in raise_if_nothing_inferred
    yield next(generator)
  File "/usr/local/lib/python3.7/site-packages/astroid/decorators.py", line 95, in wrapped
    res = next(generator)
  File "/usr/local/lib/python3.7/site-packages/astroid/inference.py", line 219, in infer_call
    yield from callee.infer_call_result(caller=self, context=callcontext)
RuntimeError: generator raised StopIteration

Expected behavior

All the lints, but no exception.

pylint --version output

Reproduces on the latest pylint and astroid:

pylint 2.4.0-dev0
astroid 2.3.0
Python 3.7.1 (default, Nov 16 2018, 22:26:09)
[GCC 6.3.0 20170516]

Originally spotted on the current release versions:

pylint 2.3.1
astroid 2.2.5
Python 3.7.3 (default, Mar 26 2019, 21:43:19)
[GCC 8.2.1 20181127]

[UncleanlyCleric]

I'm getting a similar error on one of my machines:

`Traceback (most recent call last):
File "/usr/local/lib/python3.7/site-packages/astroid/protocols.py", line 492, in _infer_context_manager
enter = next(inferred.igetattr("enter", context=context))
StopIteration

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
File "/usr/local/bin/pylint", line 10, in
sys.exit(run_pylint())
File "/usr/local/lib/python3.7/site-packages/pylint/init.py", line 20, in run_pylint
Run(sys.argv[1:])
File "/usr/local/lib/python3.7/site-packages/pylint/lint.py", line 1628, in init
linter.check(args)
File "/usr/local/lib/python3.7/site-packages/pylint/lint.py", line 943, in check
self._do_check(files_or_modules)
File "/usr/local/lib/python3.7/site-packages/pylint/lint.py", line 1075, in _do_check
self.check_astroid_module(ast_node, walker, rawcheckers, tokencheckers)
File "/usr/local/lib/python3.7/site-packages/pylint/lint.py", line 1158, in check_astroid_module
walker.walk(ast_node)
File "/usr/local/lib/python3.7/site-packages/pylint/utils.py", line 1303, in walk
self.walk(child)
File "/usr/local/lib/python3.7/site-packages/pylint/utils.py", line 1303, in walk
self.walk(child)
File "/usr/local/lib/python3.7/site-packages/pylint/utils.py", line 1303, in walk
self.walk(child)
[Previous line repeated 2 more times]
File "/usr/local/lib/python3.7/site-packages/pylint/utils.py", line 1300, in walk
cb(astroid)
File "/usr/local/lib/python3.7/site-packages/pylint/checkers/logging.py", line 215, in visit_call
result, name = is_logger_class()
File "/usr/local/lib/python3.7/site-packages/pylint/checkers/logging.py", line 197, in is_logger_class
for inferred in node.func.infer():
File "/usr/local/lib/python3.7/site-packages/astroid/decorators.py", line 141, in raise_if_nothing_inferred
yield from generator
File "/usr/local/lib/python3.7/site-packages/astroid/decorators.py", line 95, in wrapped
res = next(generator)
File "/usr/local/lib/python3.7/site-packages/astroid/inference.py", line 279, in infer_attribute
for owner in self.expr.infer(context):
File "/usr/local/lib/python3.7/site-packages/astroid/util.py", line 160, in limit_inference
yield from islice(iterator, size)
File "/usr/local/lib/python3.7/site-packages/astroid/context.py", line 113, in cache_generator
for result in generator:
File "/usr/local/lib/python3.7/site-packages/astroid/decorators.py", line 141, in raise_if_nothing_inferred
yield from generator
File "/usr/local/lib/python3.7/site-packages/astroid/decorators.py", line 95, in wrapped
res = next(generator)
File "/usr/local/lib/python3.7/site-packages/astroid/bases.py", line 137, in _infer_stmts
for inferred in stmt.infer(context=context):
File "/usr/local/lib/python3.7/site-packages/astroid/util.py", line 160, in limit_inference
yield from islice(iterator, size)
File "/usr/local/lib/python3.7/site-packages/astroid/context.py", line 113, in cache_generator
for result in generator:
File "/usr/local/lib/python3.7/site-packages/astroid/decorators.py", line 131, in raise_if_nothing_inferred
yield next(generator)
File "/usr/local/lib/python3.7/site-packages/astroid/decorators.py", line 92, in wrapped
generator = _func(node, context, **kwargs)
File "/usr/local/lib/python3.7/site-packages/astroid/inference.py", line 832, in infer_assign
stmts = list(self.assigned_stmts(context=context))
File "/usr/local/lib/python3.7/site-packages/astroid/decorators.py", line 131, in raise_if_nothing_inferred
yield next(generator)
File "/usr/local/lib/python3.7/site-packages/astroid/protocols.py", line 537, in with_assigned_stmts
yield from _infer_context_manager(self, mgr, context)
RuntimeError: generator raised StopIteration`

This only started this morning. I've tried upgrading pylint and astroid however that hasn't seemed to help.

pylint 2.3.1 astroid 2.2.5 Python 3.7.2 (default, Feb 12 2019, 08:16:38) [Clang 10.0.0 (clang-1000.11.45.5)]

[PCManticore]

Thank you for reporting this issue, I can reproduce the bug.

[nickdrozd]

Slightly simpler reproducing example:

def find_int():
    return int(([1] if True else [1])[0])

def foo():
    return find_int()
    return find_int()

x = foo()
assert True

[PCManticore]

Thanks for the report @matti-cujo This is fixed now in astroid's master.

[danihodovic]

@PCManticore when will a new astroid release be published containing this fix?

[PCManticore]

Hopefully this month @danihodovic