Microsoft/bcquality
1
0
Fork 0
mirror of https://github.com/microsoft/BCQuality.git synced 2026-08-06 09:26:52 +01:00
Code Issues Projects Releases Packages Wiki Activity Actions
bcquality/microsoft/knowledge/breaking-changes/do-not-change-published-procedure-signatures.md
Jesper Schulz-Wedde 4ca6452ccf Add breaking-changes knowledge domain and review leaf skill 
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>
2026-06-25 12:29:44 +02:00

2 KiB
Raw Blame History

bc-version domain keywords technologies countries application-area
all
breaking-changes
signature
public-procedure
parameter
return-value
overload
contract
al
w1
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.