d3cfe19d7e
Co-authored-by: Marco Borgeaud <89914223+marco-antognini-sonarsource@users.noreply.github.com>
135 lines
3.3 KiB
Plaintext
135 lines
3.3 KiB
Plaintext
This rule raises an issue when the object of a ``++with++`` statement is not a valid a context manager.
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== Why is this an issue?
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The https://docs.python.org/3/reference/compound_stmts.html#the-with-statement[``++with++`` statement] is used to wrap the execution of a block with methods defined by a context manager. The https://docs.python.org/3/reference/datamodel.html#context-managers[context manager] handles the entry into, and the exit from, the desired runtime context for the execution of the block of code. To do so, a context manager should have an ``++__enter__++`` and an ``++__exit__++`` method.
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Executing the following block of code:
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[source,python]
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----
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class MyContextManager:
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def __enter__(self):
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print("Entering")
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def __exit__(self, exc_type, exc_val, exc_tb):
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print("Exiting")
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with MyContextManager():
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print("Executing body")
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----
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will output:
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[source,text]
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----
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Entering
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Executing body
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Exiting
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----
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If either the ``++__enter__++`` or the ``++__exit__++`` method is missing, an ``AttributeError`` will be raised instead.
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=== Note
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When working with https://docs.python.org/3/reference/datamodel.html#async-context-managers[asynchronous context managers], the ``with`` statement should be replaced by ``++async with++``.
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== How to fix it
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To fix this issue, make sure that the object of the `with` statement is a valid context manager (implementing both ``++__enter__++`` and ``++__exit__++`` methods).
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If the object of the `with` statement is an asynchronous context manager, make sure to use an `async with` statement.
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== Code examples
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=== Noncompliant code example
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[source,python,diff-id=1,diff-type=noncompliant]
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----
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class MyContextManager:
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...
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with MyContextManager(): # Noncompliant: not a valid contex manager
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...
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def simple_contextmanager():
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...
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with simple_contextmanager() as e: # Noncompliant: not a valid contex manager
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...
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@asynccontextmanager
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async def async_context_manager():
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yield 42
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def call_async_context_manager():
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with async_context_manager() as context: # Noncompliant: missing "async"
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...
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----
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=== Compliant solution
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[source,python,diff-id=1,diff-type=compliant]
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----
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class MyContextManager:
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def __enter__(self):
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print("Entering")
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def __exit__(self, exc_type, exc_val, exc_tb):
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print("Exiting")
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with MyContextManager():
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...
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from contextlib import contextmanager, asynccontextmanager
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@contextmanager
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def simple_contextmanager():
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print("enter")
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yield
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print("exit")
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with simple_contextmanager() as e:
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...
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@asynccontextmanager
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async def async_context_manager():
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yield 42
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async def call_async_context_manager():
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async with async_context_manager() as context:
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...
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----
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== Resources
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=== Documentation
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* Python Documentation - https://docs.python.org/3/reference/compound_stmts.html#the-with-statement[``++with++`` statement]
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* Python Documentation - https://docs.python.org/3/reference/datamodel.html#context-managers[context managers]
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ifdef::env-github,rspecator-view[]
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'''
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== Implementation Specification
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(visible only on this page)
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=== Message
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* Replace this expression with a context manager.
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* Add "async" before "with"; Expression is an async context manager.
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=== Highlighting
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Primary: the expression used as a context manager
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Secondary: the "with" keyword
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endif::env-github,rspecator-view[]
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