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 when clauses in a case 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()
elsif a >= 10 && a < 20
doTheOtherThing()
elsif a >= 20 && a < 50
doFirstThing()
doTheThing() # Noncompliant; duplicates first condition
else
doTheRest()
end
case i
when 1
doFirstThing()
doSomething()
when 2
doSomethingDifferent()
when 3 # Noncompliant; duplicates case 1's implementation
doFirstThing()
doSomething()
else
doTheRest()
end
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()
elsif a >= 10 && a < 20
doTheOtherThing()
else
doTheRest()
end
- for a
case, the values should be put in the when expression list.
case i
when 1, 3
doFirstThing()
doSomething()
when 2
doSomethingDifferent()
else
doTheRest()
end
Exceptions
Blocks in an if chain that contain a single line of code are ignored, as are blocks in a case statement that contain a
single line of code.
if a ==
doSomething() # no issue, usually this is done on purpose to increase the readability
elsif a == 2
doSomethingElse()
else
doSomething()
end
But this exception does not apply to if chains without else-s, or to case-es without else
clauses when all branches have the same single line of code. In the case of if chains with else-s, or of
case-es with else clauses, rule S3923 raises a bug.
if a == 1
doSomething() # Noncompliant, this might have been done on purpose but probably not
elsif a == 2
doSomething()
end
