rspec/rules/S5747/python/rule.adoc

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

== 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:

[source,python]
----
def foo():
    try:
        ...
    except ValueError as e:
        raise # this will re-raise "e"
----

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` block, the exception caught by the `except` will be re-raised. However, this behavior is not reliable as nothing prevents a developer from calling the function from a different context. 

Overall, having bare `raise` statements outside of `except` blocks is discouraged as it is hard to understand and maintain.

=== Notes

In a `finally` block, an exception is still active only when it hasn't been caught in a previous `except` clause or if it has been raised in an `except` block. In both cases, it is better to let the exception propagate automatically than to re-raise it. This pattern is covered by rule S5704.


== How to fix it

To fix this issue, make sure to specify which exception needs to be raised when outside of an `except` block.

=== Code examples

==== Noncompliant code example

[source,python,diff-id=1,diff-type=noncompliant]
----
raise  # Noncompliant: no active exception

def foo():
    raise  # Noncompliant: no active exception
    try:
        raise  # Noncompliant: no active exception
    except ValueError:
        handle_error()

def handle_error():
    raise  # Noncompliant: this is not reliable
----


==== Compliant solution

[source,python,diff-id=1,diff-type=compliant]
----
raise ValueError()

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

== Resources

=== Documentation

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


ifdef::env-github,rspecator-view[]

'''
== Implementation Specification
(visible only on this page)

=== Message

Remove this "raise" statement or move it inside an "except" block.


=== Highlighting

The raise statement


'''
== Comments And Links
(visible only on this page)

=== relates to: S5704

=== relates to: S5706

=== is related to: S1039

endif::env-github,rspecator-view[]