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* Add P0 extensibility compatibility knowledge Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: 645349fd-1892-48f3-8a84-db77d6abd1c3 * Correct event compatibility guidance Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: 645349fd-1892-48f3-8a84-db77d6abd1c3 --------- Co-authored-by: Jesper Schulz-Wedde <jesper.schulzwedde@microsoft.com>
26 lines
2 KiB
Markdown
26 lines
2 KiB
Markdown
---
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bc-version: [all]
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domain: events
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keywords: [local-event, internal-event, event-subscriber, compatibility, access-modifier, integration-event, business-event, parameter-name, var-parameter, appsourcecop]
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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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# Treat local and internal events as subscriber contracts
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## Description
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The `local` and `internal` access modifiers on Business and Integration event publishers restrict who can raise the procedure; they do not prevent dependent extensions from subscribing. Once shipped, the event name and each existing parameter's name, type/subtype, and value-versus-`var` passing mode are compatibility contracts even when the publisher is not public. Parameter order is not a subscriber contract because subscribers bind the parameters they use by name. This differs from `[InternalEvent]`, which is module-only except for modules named by `internalsVisibleTo`.
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## Best Practice
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Preserve a shipped Business or Integration event's identity and every existing parameter's name, type/subtype, and passing mode regardless of the procedure access modifier. AS0025 protects names and types, while AS0063 and AS0077 protect removal and addition of `var`. New parameters may be added at any position on a `local` or `internal` event because subscribers can omit them; public event procedures follow the stricter caller contract described by `add-new-event-parameters-at-the-end`.
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See sample: `treat-local-and-internal-events-as-subscriber-contracts.good.al`.
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## Anti Pattern
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Renaming or removing an existing parameter, changing its type/subtype, or adding/removing its `var` modifier because the event publisher procedure is `local` or `internal`. AppSourceCop checks these subscriber-breaking changes because dependent event subscribers can still bind to the event. Reordering unchanged parameters, or inserting a new parameter among them, is not this anti-pattern.
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See sample: `treat-local-and-internal-events-as-subscriber-contracts.bad.al`.
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