When the same code is duplicated in two or more separate branches of a conditional, it can make the code harder to understand, maintain, and can
potentially introduce bugs if one instance of the code is changed but others are not.
Having two cases in a switch statement or two branches in an if chain with the same implementation is at
best duplicate code, and at worst a coding error.
if (a >= 0 && a < 10) {
doFirstThing
doTheThing
}
else if (a >= 10 && a < 20) {
doTheOtherThing
}
else if (a >= 20 && a < 50) {
doFirstThing
doTheThing // Noncompliant; duplicates first condition
}
else {
doTheRest
}
value match {
case 1 =>
doFirstThing
doSomething
case 2 =>
doSomethingDifferent
case 3 => // Noncompliant; duplicates case 1's implementation
doFirstThing
doSomething
case _ =>
doTheRest
}
If the same logic is needed for both instances, then:
- in an
if structure they should be combined
if ((a >= 0 && a < 10) || (a >= 20 && a < 50)) {
doFirstThing
doTheThing
}
else if (a >= 10 && a < 20) {
doTheOtherThing
}
else {
doTheRest
}
- for a
match, the values should be put in the case expression list.
value match {
case 1 | 3 =>
doFirstThing
doSomething
case 2 =>
doSomethingDifferent
case _ =>
doTheRest
}
Exceptions
Blocks in an if chain that contain a single line of code are ignored, as are blocks in a match statement that contain a
single line of code.
if(a == 1) {
doSomething //no issue, usually this is done on purpose to increase the readability
} else if (a == 2) {
doSomethingElse
} else {
doSomething
}
But this exception does not apply to if chains without else-s, or to match-es without default clauses when
all branches have the same single line of code. In case of if chains with else-s, or of match-es with default
clauses, rule S3923 raises a bug.
if(a == 1) {
doSomething //Noncompliant, this might have been done on purpose but probably not
} else if (a == 2) {
doSomething
}
