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 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 AND a < 10.
doFirst.
doTheThing.
ELSEIF a >= 10 AND a < 20.
doTheOtherThing.
ELSEIF a >= 20 AND a < 50.
doFirst. // Noncompliant; duplicates first condition
doTheThing.
ENDIF.
CASE i.
WHEN 1.
doFirst.
doSomething.
WHEN 2.
doSomethingDifferent.
WHEN 3. // Noncompliant; duplicates case 1's implementation
doFirst.
doSomething.
WHEN OTHERS.
doTheRest.
ENDCASE.
If the same logic is needed for both instances the conditions should be combined.
IF (a >= 0 AND a < 10) OR (a >= 20 AND a < 50).
doFirst.
doTheThing.
ELSEIF a >= 10 AND a < 20.
doTheOtherThing.
ENDIF.
CASE i.
WHEN 1 OR 3.
doFirst.
doSomething.
WHEN 2.
doSomethingDifferent.
WHEN OTHERS.
doTheRest.
ENDCASE.
Exceptions
Blocks in an IF chain or in CASE statement that contain a single line of code are ignored.
IF a >= 0 AND a < 10.
doTheThing.
ELSEIF a >= 10 AND a < 20.
doTheOtherThing.
ELSEIF a >= 20 AND a < 50.
doTheThing. // no issue, usually this is done on purpose to increase the readability
ENDIF.
But this exception does not apply to IF chains without final ELSE-s, or to CASE-s without WHEN
OTHERS clauses when all branches have the same single line of code. In case of IF chains with ELSE-s, or of
CASE-s with WHEN OTHERS clauses, rule S3923 raises a bug.
IF a >= 0 AND a < 10. //Noncompliant, this might have been done on purpose but probably not
doTheThing.
ELSEIF a >= 10 AND a < 20.
doTheThing.
ENDIF.
