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AL gives no short-circuit (lazy) evaluation guarantee for and/or/xor — neither the AL operators nor the boolean operators documentation defines a lazy evaluation order. LLMs trained on C#, JavaScript, or SQL assume the left operand guards the right, which produces conditions where a guard does not protect an unsafe subscript or a field read after a failed Get, and where an expensive operand is paid on every path. Adds community/knowledge/performance/boolean-operators-do-not-short-circuit.md with good/bad AL companions. The guidance prefers nested if when one operand depends on another, while keeping and/or legitimate for operands that are independently safe and cheap, so a reviewer does not flag harmless bound checks. This is the first article in a community performance domain; the Microsoft performance review leaf skill already sources candidates by domain across every enabled layer, so no skill change is needed to reach it. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
18 lines
850 B
AL
18 lines
850 B
AL
codeunit 50541 "Perf Sample NoShortCircuit Bad"
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{
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procedure ExceedsThreshold(var Thresholds: array[10] of Decimal; Index: Integer; Amount: Decimal): Boolean
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begin
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// Thresholds[Index] is evaluated even when Index is 0, so the leading range
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// check does not prevent the subscript from being read out of range.
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exit((Index >= 1) and (Index <= ArrayLen(Thresholds)) and (Amount > Thresholds[Index]));
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end;
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procedure IsBlockedCustomer(CustomerNo: Code[20]): Boolean
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var
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Customer: Record Customer;
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begin
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// The Get runs even for an empty CustomerNo, and Blocked is read even when the
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// Get failed, so the result is taken from a record that was never loaded.
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exit((CustomerNo <> '') and Customer.Get(CustomerNo) and (Customer.Blocked <> Customer.Blocked::" "));
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end;
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}
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