bcquality/custom/knowledge/patterns/cmfrt-case-requires-else.md

bc-version	domain	keywords	technologies	countries	application-area
all	patterns	case else defensive-coding unhandled-case enum option silent-failure	al	w1	all

CMFRT CASE statement requires ELSE clause

Description

Every case statement in CMFRT AL code must include an else clause. The rule is unconditional: even when every currently known value of the matched expression is enumerated, the else clause guards against future values being added to an enum, option field, or integer range. Without else, a new value passes through the case block silently — no error, no action — and the resulting silent no-op or data corruption is difficult to trace because the case appears correct at the time it was written.

Best Practice

Always add an else clause to every case statement. When no meaningful action applies to unexpected values, the else clause should raise an error that identifies the unexpected value, log it, or call a dedicated handler procedure. The key outcome is that the unexpected case is detected at runtime rather than silently ignored.

See sample: cmfrt-case-requires-else.good.al.

Anti Pattern

Writing a case statement that enumerates all currently known values and omits else. The code appears complete but becomes a silent failure mode the moment a new enum value is added by a future developer or by a base application update, because the added value simply falls through the entire case block.

See sample: cmfrt-case-requires-else.bad.al.