Status Variable

Status Variables are mutable primitives that are initialized before an operation to store some information based on the process and are later used as a switch for some action.

The Status Variables can be identified as a distinct code smell, although they are just a signal for five other code smells:

• Clever Code,
• Imperative Loops,
• Afraid To Fail,
• Mutable Data,
• Special Case.

They come in different types and forms, but common examples are the success: bool = False-s before performing an operation block or i: int = 0 before a loop statement. The code that has them increases in complexity by a lot, and usually for no particular reason because there most likely exists a proper solution using first-class functions. Sometimes, they clutter the code, demanding other methods or classes to make additional checks before execution resulting in Required Setup/Teardown Code.

Causation

The developer might have special cases that could be handled only inside a loop and could not figure out a better solution.

Problems

Comprehensibility

It is more difficult to understand the inner workings of a method than the declarative solution.

Examples

def find_foo_index(names: list[str]):
    found = False
    i = 0
    while not found:
        if names[i] == 'foo':
            found = True
        else:
            i += 1
    return i

def find_foo_index(names: list[str]):
    for index, value in enumerate(names):
        if value == 'foo':
            return index

def find_foo_index(names: list[str]):
    return names.index('foo')

Refactoring:

• Replace with Built-In
• Extract Method
• Remove Status Variables

Sources

• [Origin] - Marcel Jerzyk, "Code Smells: A Comprehensive Online Catalog and Taxonomy" (2022)