bcquality/microsoft/knowledge/events/publish-thin-onbefore-onafter-integration-events.md
Jesper Schulz-Wedde f19f0618fb
Add events knowledge domain and review leaf skill (#43)
* Add events knowledge domain and review leaf skill

Add a new `events` knowledge domain covering AL events & subscribers,
wired into the AL review pipeline.

- 3 atomic articles (+ .good.al/.bad.al samples) under
  microsoft/knowledge/events/: the IsHandled override pattern, thin
  OnBefore/OnAfter integration-event publishers, and static vs manual
  subscribers.
- New leaf skill microsoft/skills/review/al-events-review.md sourcing the
  events domain.
- Wired into microsoft/skills/review/al-code-review.md (sub-skills + Source
  + description) and README.md (leaf-skill count + domain list).

AL event syntax verified against Microsoft Learn. Samples are
demonstration-only (not compiled by CI). Additive change; no contract change.

Part of #34.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Add 12 general AL event-design articles to events domain

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>

* Refine events articles after review feedback

Correct wording in five events articles to reflect that AL event
subscribers bind by parameter name, not position:

- add-new-event-parameters-at-the-end: drop the inaccurate claim that
  appending a parameter forces subscribers to be updated or causes wrong
  values; keep the append-at-end best practice.
- do-not-add-ishandled-to-an-existing-event: reframe from "breaking
  change" to the semantic/purpose shift that leaves existing subscribers
  pointless; rename the breaking-change keyword to semantic-change.
- name-events-by-publisher-position: extend the good sample with
  position-named publishers raised from table and report trigger
  contexts.
- initialize-ishandled-to-false-before-publishing: scope the detection
  and best practice to events that actually carry a var IsHandled, so an
  OnBefore with no IsHandled is not flagged.
- do-not-bypass-critical-operations-with-ishandled: add a litmus-test
  definition of a critical operation (code that cannot stand as an
  independent, self-contained unit).

Knowledge-only; no contract or wiring change.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Soften Anti Pattern wording in add-new-event-parameters article

Remove the last name-vs-position misconception from the Anti Pattern so it
is consistent with the corrected Description: mid-list insertion is framed
as noisy and harder to review rather than as forcing subscriber re-mapping.
Detection sentence unchanged.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Add events domain reviewers to CODEOWNERS

Add @AleksandricMarko and @pchriste-microsoft-com as required reviewers
for the events knowledge domain, matching the existing per-domain expert
ownership convention. Inserted in alphabetical order ahead of the
performance line.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

---------

Co-authored-by: Jesper Schulz-Wedde <jesper.schulzwedde@microsoft.com>
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
2026-06-25 12:24:25 +02:00

2.2 KiB

bc-version domain keywords technologies countries application-area
all
events
integration-event
onbefore
onafter
extension-point
thin-publisher
publisher-body
extensibility
al
w1
all

Publish thin OnBefore/OnAfter integration events to expose extension points

Description

A key operation — a posting, release, or validation routine — becomes a hard wall for partners when it ships no integration events: the only way to change it is to overwrite or duplicate the base code. The Business Central remedy is to raise thin OnBeforeX/OnAfterX integration events at the operation's boundaries, passing var Rec and the relevant parameters so subscribers have what they need. An equally common defect is the inverse: putting business logic inside the publisher method body. An event publisher is a hook, not a procedure — its body must be empty, and the platform even forbids variables, return values, and code other than comments in it. LLMs both omit the extension points and, when they do add an event, wrongly fill its body with logic.

Best Practice

Wrap the operation's core with events: raise OnBeforeX(var Rec, var IsHandled) before the default work and OnAfterX(var Rec) once it succeeds, at the natural boundaries of the routine. Declare each publisher [IntegrationEvent(false, false)] local procedure with an empty body and let the calling routine — never the publisher — own the logic. Pass records by var so subscribers can read and adjust them, and include the parameters a subscriber would need to act. This gives partners a stable seam without touching base code.

See sample: publish-thin-onbefore-onafter-integration-events.good.al.

Anti Pattern

Business logic placed inside an [IntegrationEvent] publisher method, so the "event" actually mutates state every time it is raised — defeating the hook and surprising every reader — or a core operation that exposes no extension points at all, forcing partners to overwrite or duplicate it. Detection: an [IntegrationEvent]/[BusinessEvent] method whose body contains statements rather than being empty, or a posting/validation routine with no surrounding OnBefore/OnAfter publishers.

See sample: publish-thin-onbefore-onafter-integration-events.bad.al.