Special Case

Also known as: Complex Conditional

Change Preventers Conditional Logic Code Smell Implementation Smell Within Class

The if-statement that handles "one weird edge case" before the real logic begins. It was a hotfix once. It was never properly refactored. Now every future reader has to hold that branch in their...

1 min read April 19, 2022 1 source

Overview

Wake addresses the complex conditional situation as a Special Case code smell with two symptoms - a complex if statement and/or value checking before doing the actual work [1].

There was a need for a special case to handle. A hotfix that was never adequately fixed could also be the reason for the smell.

Problems

📖

Comprehensibility

The method is doing a specific task, but there is "one special case" to consider.

🧩

Increased Test Complexity

Special case has to have an extra special test.

Example

def parse_foo(foo: Foo) -> Goo:
    if 'zoo' in foo.sample_attribute:
        ...
        ...
        ...

    ...
    ...
    ...
    ...

PYTHON

Recursive methods always have to have a base case to stop the recursion.

---

Refactoring

Consolidate Conditional Expression
Replace Conditional with Polymorphism
Introduce Null Object
Replace Exception with Test

Sources

ORIGIN
William C. Wake
Refactoring Workbook
2004 · ISBN 978-0321109293

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