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Review feedback: the five value sets sharing exit(false) should be comma separated. Applied to the three that are pure field reads with no order dependency. The Get and the Blocked read keep their own value sets. The documentation guarantees that the first matching value set executes, which orders matching across separate value sets; it says nothing about evaluation within one comma-separated set, and the natural lowering of that is an equality-or chain — where AL's or does not short-circuit. Grouping the Get with the checks that must precede it would rest the sample's correctness on undocumented behaviour, which is the defect these two articles exist to prevent. Encodes the boundary in the Best Practice section so the grouping is applied where it is safe and not where it is not, and scopes the repeated-exit detection signal explicitly to nested chains so the case sample does not read as its own anti-pattern. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
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Use case true of for long chains of dependent conditions
Description
Because AL gives no short-circuit guarantee for and and or, a chain of conditions that must be evaluated in order has to be sequenced with nested if statements — and past three conditions the nesting itself becomes the problem: the body drifts right, the order of evaluation is carried by indentation alone, and any shared failure path is repeated at every level. AL's case statement is the flat alternative. Its value sets "must be an expression or a range", so case true of and case false of accept arbitrary boolean expressions, and the statement "is evaluated, and the first matching value set executes the associated statement" — evaluation stops at the first match, which is exactly the laziness the boolean operators do not provide.
Best Practice
Sequence two or three dependent conditions with nested if. Beyond that, switch to case: use case false of for a chain of guards where every condition must hold, listing the failure action per condition and letting control fall past end when all pass; use case true of for first-match dispatch, where each later probe runs only if the earlier ones did not match. Value sets that share an action may be comma-separated into one value set, but only when each is a pure, order-independent test — a field comparison or an enum check. A condition with a side effect, or one that is only safe after an earlier condition passed, keeps its own value set even when its action repeats, because ordered matching is guaranteed across value sets, not within one. This keeps every condition at one indentation level, makes evaluation order explicit rather than implied by nesting, and preserves the stop-at-first-match behaviour. It also aligns with the AL programming convention that more than two alternatives belong in a case statement rather than an if-then-else.
See sample: case-true-of-for-long-condition-chains.good.al.
Anti Pattern
An if ladder four or more levels deep whose only purpose is sequencing guards. Detection: a chain of nested if statements with no else, each condition guarding the one below it, terminating in a single action or exit; or the same exit/error duplicated at every level of such a nested chain, purely to escape it. The second, worse form is collapsing that ladder into one and chain to escape the nesting — that trades indentation for a real defect, because the operands are still all evaluated. Reach for case instead of either.
See sample: case-true-of-for-long-condition-chains.bad.al.
See also
boolean-operators-do-not-short-circuit.md covers the underlying evaluation rule that makes the sequencing necessary in the first place.