TernaryCouldBeElvis.md

Pattern: Use of ternary instead of Elvis expression

Issue: -

Description

Checks for ternary expressions where the boolean and true expressions are the same. These can be simplified to an Elvis expression.

Example of violations:

x ? x : false               // violation; can simplify to x ?: false

foo() ? foo() : bar()       // violation; can simplify to foo() ?: bar()
foo(1) ? foo(1) : 123       // violation; can simplify to foo(1) ?: 123

(x == y) ? same : diff      // OK
x ? y : z                   // OK
x ? x + 1 : x + 2           // OK
x ? 1 : 0                   // OK
x ? !x : x                  // OK
!x ? x : null               // OK

foo() ? bar() : 123         // OK
foo() ? foo(99) : 123       // OK
foo(x) ? foo() : 123        // OK
foo(1) ? foo(2) : 123       // OK

NOTE: If the boolean and true expressions are the same method call, and that method call has side-effects, then converting it to a Elvis expression may produce different behavior. The method will only be called once, rather than twice. But relying on those side-effects as part of a ternary expression behavior is confusing, error-prone and just a bad idea. In any case, that code should be refactored to move the reliance on the side-effects out of the ternary expression.

Further Reading

• CodeNarc - TernaryCouldBeElvis