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Seed a new breaking-changes (AL API stability) knowledge domain with six articles plus good/bad AL samples, a new al-breaking-changes-review leaf skill, and minimal wiring into al-code-review and the README. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
26 lines
2 KiB
Markdown
26 lines
2 KiB
Markdown
---
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bc-version: [all]
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domain: breaking-changes
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keywords: [access-modifier, internal, local, public, protected, scope, encapsulation]
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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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# Choose access modifiers deliberately
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## Description
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Access is a decision about what you are willing to support forever. The moment a procedure or object is reachable from another extension — no `local`, or a removed `[Scope('OnPrem')]` — it becomes a contract: callers bind to it, and changing or removing it later is a breaking change. The safe default is the narrowest access that works. Use `local` for implementation detail confined to one object, `internal` for code shared within the app but not exposed to consumers, and `protected var` for state intended as an inheritance point for extension objects. Reserve `public` for the deliberate, supported entry points you intend to maintain as a stable API. LLMs tend to make everything public "to be safe," which inverts the rule and turns every helper into an accidental contract.
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## Best Practice
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Start everything `local` or `internal` and promote a member to `public` only when you have decided to support it as a stable contract. Expose a small, intentional surface — the supported entry point — and keep validation, posting, and helper routines `internal` for in-app reuse or `local` when single-object. Do not drop `[Scope('OnPrem')]` without intent, since that too widens the contract. Every public member is a maintenance commitment; spend them deliberately.
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See sample: `choose-access-modifiers-deliberately.good.al`.
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## Anti Pattern
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Declaring every procedure `public` by default, so internal helpers like `ValidateOrder` and `PostOrder` become a de-facto API that consumers bind to and that can no longer be changed freely. Detection: an object where implementation-detail procedures carry no access modifier or are `public` without a reason to support them externally. Default them to `internal`/`local` and make only the intended entry point public.
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See sample: `choose-access-modifiers-deliberately.bad.al`.
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