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Add 12 atomic knowledge articles under microsoft/knowledge/events covering general AL event-design best practices: IsHandled initialization and OnAfter preservation, appending new event parameters, position-based event naming, reusing/extending events, avoiding per-iteration publishing, Temp-prefixing temporary record parameters, unabbreviated parameter names, preferring the this keyword over IncludeSender, avoiding loosely typed parameters, not mutating existing event contracts, and not bypassing critical operations with IsHandled. Each article ships a .good.al and .bad.al demonstration sample (object IDs 50240-50296; not compiled by CI). Extend the al-events-review leaf Worklist with one targeted check per new rule. Additive only; no contract or wiring change (events leaf already wired). Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
26 lines
1.8 KiB
Markdown
26 lines
1.8 KiB
Markdown
---
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bc-version: [all]
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domain: events
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keywords: [ishandled, initialization, deterministic, onbefore, reset, integration-event, control-flow]
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technologies: [al]
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countries: [w1]
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application-area: [all]
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---
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# Initialize IsHandled to false before publishing
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## Description
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A routine that raises an `OnBefore…` integration event with a `var IsHandled: Boolean` parameter passes that variable in by reference, so its incoming value decides whether the default logic is skipped. A freshly declared Boolean starts as `false`, but the same variable is frequently reused to raise several events in one routine, and after the first raise it may already be `true`. Assigning `IsHandled := false;` on the line immediately before every raise makes the control flow deterministic and self-documenting, and prevents a stale `true` from silently suppressing logic the author never meant to make skippable. Generated code often reuses one `IsHandled` across several raises without resetting it.
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## Best Practice
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Set `IsHandled := false;` immediately before each `OnBeforeX(…, IsHandled)` raise, then guard the default logic with `if IsHandled then exit;` or `if not IsHandled then …`. Do this even when the variable was just declared: the explicit reset documents intent and stays correct if a second event raise is added to the routine later.
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See sample: `initialize-ishandled-to-false-before-publishing.good.al`.
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## Anti Pattern
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Raising `OnBeforeX(…, IsHandled)` with a variable whose value carries over from an earlier raise, so a subscriber that handled the first event unintentionally suppresses the second routine's default logic. Detection: an `IsHandled` variable passed to more than one event in a routine without an intervening `IsHandled := false;`, or any `OnBefore…` raise not preceded by an explicit reset.
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See sample: `initialize-ishandled-to-false-before-publishing.bad.al`.
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