16f6c0aecf
Inline adoc files when they are included exactly once. Also fix language tags because this inlining gives us better information on what language the code is written in.
72 lines
2.4 KiB
Plaintext
72 lines
2.4 KiB
Plaintext
== Why is this an issue?
|
||
|
||
https://docs.python.org/3/library/exceptions.html#SystemExit[``++SystemExit++``] is raised when https://docs.python.org/3/library/sys.html#sys.exit[``++sys.exit()++``] is called. https://docs.python.org/3/library/exceptions.html#KeyboardInterrupt[``++KeyboardInterrupt++``] is raised when the user asks the program to stop by pressing interrupt keys. Both exceptions are expected to propagate up until the application stops.
|
||
|
||
|
||
In order to avoid catching ``++SystemExit++`` and ``++KeyboardInterrupt++`` by mistake https://www.python.org/dev/peps/pep-0352/#exception-hierarchy[PEP-352] created the root class ``++BaseException++`` from which ``++SystemExit++``, ``++KeyboardInterrupt++`` and ``++Exception++`` derive. Thus developers can use ``++except Exception:++`` without preventing the software from stopping.
|
||
|
||
|
||
The ``++GeneratorExit++`` class also derives from ``++BaseException++`` as it is not really an error and is not supposed to be caught by user code.
|
||
|
||
|
||
As said in https://docs.python.org/3/library/exceptions.html#BaseException[Python's documentation], user-defined exceptions are not supposed to inherit directly from ``++BaseException++``. They should instead inherit from ``++Exception++`` or one of its subclasses.
|
||
|
||
|
||
This rule raises an issue when a class derives from one of the following exception classes: ``++BaseException++``, ``++KeyboardInterrupt++``, ``++SystemExit++`` or ``++GeneratorExit++``.
|
||
|
||
|
||
=== Noncompliant code example
|
||
|
||
[source,python]
|
||
----
|
||
class MyException(BaseException): # Noncompliant
|
||
pass
|
||
|
||
class MyException(GeneratorExit): # Noncompliant
|
||
pass
|
||
|
||
class MyException(KeyboardInterrupt): # Noncompliant
|
||
pass
|
||
|
||
class MyException(SystemExit): # Noncompliant
|
||
pass
|
||
----
|
||
|
||
|
||
=== Compliant solution
|
||
|
||
[source,python]
|
||
----
|
||
class MyException(Exception):
|
||
pass
|
||
----
|
||
|
||
|
||
== Resources
|
||
|
||
* PEP 352 – https://www.python.org/dev/peps/pep-0352/#exception-hierarchy-changes[Required Superclass for Exceptions]
|
||
* Python Documentation - https://docs.python.org/3/library/exceptions.html#BaseException[BaseException class]
|
||
|
||
ifdef::env-github,rspecator-view[]
|
||
|
||
'''
|
||
== Implementation Specification
|
||
(visible only on this page)
|
||
|
||
=== Message
|
||
|
||
Derive this class from "Exception" instead of BaseException/GeneratorExit/KeyboardInterrupt/SystemExit
|
||
|
||
|
||
=== Highlighting
|
||
|
||
The forbidden parent class reference.
|
||
|
||
|
||
class Foo(BaseException)
|
||
|
||
^^^^^^^^^^^^^^^
|
||
|
||
|
||
endif::env-github,rspecator-view[]
|