rspec/rules/S5747/python/rule.adoc

== Why is this an issue?

A bare ``++raise++`` statement, i.e. a ``++raise++`` with no exception provided, will re-raise the last active exception in the current scope. If the "raise" statement is not in an ``++except++`` or ``++finally++`` block, no exception is active and a ``++RuntimeError++`` is raised instead.


If the bare ``++raise++`` statement is in a function called in an ``++except++`` statement, the exception caught by the ``++except++`` will be raised. This works but is hard to understand and maintain. Nothing indicates in the parent ``++except++`` that the exception will be reraised, and nothing prevents a developer from calling the function in another context.


Note also that using a bare ``++raise++`` in a ``++finally++`` block only works when an exception is active, i.e. when an exception from the ``++try++`` block is not caught or when an exception is raised by an ``++except++`` block. It will fail in any other case and should not be relied upon. This code smell is handled by rule S5704.


This rule raises an exception when a bare ``++raise++`` statement is not in an ``++except++`` or ``++finally++`` block.


=== Noncompliant code example

[source,python]
----
raise  # Noncompliant

def foo():
    raise  # Noncompliant
    try:
        raise  # Noncompliant
    except ValueError as e:
        handle_error()
    except:
        raise
    else:
        raise  # Noncompliant
    finally:
        raise

def handle_error():
    raise  # Noncompliant. This works but is hard to understand.
----


=== Compliant solution

[source,python]
----
raise ValueError()

def foo():
    raise ValueError()
    try:
        raise ValueError()
    except:
        raise
    else:
        raise ValueError()
    finally:
        raise
----


== Resources

* Python Documentation - https://docs.python.org/3/reference/simple_stmts.html#raise[The ``++raise++`` statement]


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