[Adjust Rule] SIM401 False positive, rule too greedy

[joaoe]

Desired change

• Rule(s): SIM401
• Adjustment: The rule is too greedy and will happily trigger in code that has nothing to do with the supposed suggested simplification in the documentation

Example

This testcase shows the false posivie

container_1 = unrelated_container, expensive_side_effect = None
key = "value"
if key in container_1 :
    retval = unrelated_container[key]
else:
    retval  = expensive_side_effect()

Output

sim401_bug.py:3:1: SIM401 Use 'retval = container_1.get(key, expensive_side_effect())' instead of an if-block

Issues with the rule

1. container_1 is not a dict, could be any generic container
2. the variable accessed inside the if block is not the same one in the condition
3. the else block is non-trival code with side-effects

Suggestion

The rule should only trigger in the very strict case

if key in container:
    retval = container[key]
else:
    retval  = "value"

Where

1. container must be accessed in both the condition with the form key in container and then the if block container[key]
2. key must be reused both in the condition and if block
3. "value" must be a literal or simple variable name e.g. "value" or value. Else, stuff like value.property or value() can have side-effects which change the state of the application.