rspec/rules/S5650/python/rule.adoc

== Why is this an issue?

The https://docs.python.org/3/reference/compound_stmts.html#the-with-statement[``++with++`` statement] should only be used with https://docs.python.org/3/reference/datamodel.html#context-managers[context managers]. A context manager should have an ``++__enter__++`` and an ``++__exit__++`` method.


Note that only ``++async with++`` statements should be used on https://docs.python.org/3/reference/datamodel.html#async-context-managers[asynchronous context managers].


This rule raises an issue when a ``++with++`` statement is used on something else than a context manager.


=== Noncompliant code example

[source,python]
----
from contextlib import contextmanager, asynccontextmanager

def generator():
    yield 42

with generator() as e:  # Noncompliant
    print(e)

class Empty:
    pass

with Empty():  # Noncompliant
    pass

@asynccontextmanager
async def async_context_manager():
    yield 42

with async_context_manager() as context:  # Noncompliant Missing "async"
    print(context)

----


=== Compliant solution

[source,python]
----
from contextlib import contextmanager, asynccontextmanager

@contextmanager
def simple_contextmanager():
    print("enter")
    yield
    print("exit")

with simple_contextmanager() as e:
    print(e)

class SimpleContextManager:
    def __enter__(self):
        print("enter")
    def __exit__(self, type_, value, traceback):
        print("exit")

with SimpleContextManager():
    pass

@asynccontextmanager
async def async_context_manager():
    yield 42

async def call_async_context_manager():
    async with async_context_manager() as context:
        print(context)

asyncio.run(call_async_context_manager())
----

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== Implementation Specification
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