mirror of
https://github.com/microsoft/BCQuality.git
synced 2026-08-06 17:36:53 +01:00
6140a52b03
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: Jesper Schulz-Wedde <jesper.schulzwedde@microsoft.com> Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
26 lines
2 KiB
Markdown
26 lines
2 KiB
Markdown
---
|
|
bc-version: [all]
|
|
domain: breaking-changes
|
|
keywords: [signature, public-procedure, parameter, return-value, overload, contract]
|
|
technologies: [al]
|
|
countries: [w1]
|
|
application-area: [all]
|
|
---
|
|
|
|
# Do not change the signature of a published procedure
|
|
|
|
## Description
|
|
|
|
A procedure that is reachable from outside its object — any procedure not marked `local` (and, for on-prem-scoped code, anything a dependent app can still bind to) — is a contract. Once another extension compiles against it, changing its shape breaks that extension at build time. Signature changes include adding, removing, or reordering parameters, changing a parameter or return type, and toggling a parameter between by-value and `var` (by-reference). The platform treats the procedure's identity as its full signature, so even a "compatible-looking" tweak is a new method to dependents. There is exactly one safe edit: naming a previously unnamed return value, which adds no caller obligation. LLMs routinely "improve" a public procedure in place by adding a parameter, not realizing every consumer must be recompiled.
|
|
|
|
## Best Practice
|
|
|
|
Treat a published signature as frozen. When new behavior needs more inputs, add a new procedure or overload alongside the original — for example a `CalculateDiscountWithRate(Amount; Rate)` next to the unchanged `CalculateDiscount(Amount)` — and let the old one delegate to the new one. Existing callers keep compiling; new callers opt into the richer entry point. Naming an unnamed return value is the one in-place change that is always safe.
|
|
|
|
See sample: `do-not-change-published-procedure-signatures.good.al`.
|
|
|
|
## Anti Pattern
|
|
|
|
Editing the existing public procedure's parameter list — here, adding a `Rate` parameter to `CalculateDiscount` — so every dependent extension that called the old form fails to compile. Detection: a parameter added, removed, reordered, retyped, or flipped to/from `var`, or a changed return type, on any non-`local` procedure that already shipped. Add a new overload instead.
|
|
|
|
See sample: `do-not-change-published-procedure-signatures.bad.al`.
|