[New Rule] Don't check list length is > 0 before iterating over it

[rpdelaney]

Explanation

Looking at one's own old, bad code can be a source of great cringe.

• I remember prepending if incidents is not None because if incidents is None, then a TypeError is raised on the second condition. This line can be reduced to if incidents: without any change in behavior.

• Checking the list length before iterating over it is a no-op.

Example

# Bad
incidents = get_ticket_ids(cell.value)
if incidents is not None and len(incidents) > 0:
    for incident in incidents:
        print(incident)

# Good
incidents = get_ticket_ids(cell.value)
if incidents:
    for incident in incidents:
        print(incident)

# Good
if incidents := get_ticket_ids(cell.value):
    for incident in incidents:
        print(incident)

[rpdelaney]

Prior art:

• PIE787