bcquality/microsoft/knowledge/upgrade/enum-values-additive-at-end.md
Jesper Schulz-Wedde a9f3c50863 Regenerate microsoft/knowledge from upstream BCApps instructions
The previous LLM-generated knowledge files contained factual
hallucinations. The most visible was the claim that `FindFirst` /
`FindLast` "forces a full-table scan" on an unfiltered record - it does
not; those APIs return a single row via the current key.

Other inaccuracies the audit found and fixed:

* `FindSet(true)` was described as "taking a LockTable". The correct
  upstream phrasing is that `FindSet(true)` sets
  `ReadIsolation::UpdLock` on the read. UpdLock and LockTable are
  related but distinct mechanisms.
* The list of production-scale tables had been invented beyond the
  upstream source (e.g. "Detailed Cust. Ledg. Entry") without a
  citation. The regenerated list matches the ten tables upstream lists
  with their P95 row counts.
* `SetLoadFields` guidance had been augmented with an extra mechanism
  claim ("the database resolves the filter using the index without
  hydrating the value") not present in upstream.

Approach: full regeneration of `microsoft/knowledge/` from the six
upstream BCApps Code Review instruction files, with Microsoft Learn /
the AL language reference as a secondary source. Every claim in every
regenerated file is anchored to a verbatim upstream quote (or a Learn
URL); the audit trail lives in artifacts/trace-<domain>.json on the
session workspace.

The PR #11 transaction/error-handling cluster is preserved verbatim:

* performance/understand-implicit-transaction-boundary.md
* performance/codeunit-run-as-atomic-sub-operation.{md,good.al,bad.al}
* performance/codeunit-run-requires-prior-commit-inside-transaction.{md,good.al,bad.al}
* performance/use-tryfunction-for-error-catching-not-rollback.{md,good.al,bad.al}
* performance/avoid-commit-inside-loops.{md,good.al,bad.al}
* security/commitbehavior-attribute-scopes-explicit-commits.{md,good.al,bad.al}
* testing/transactionmodel-attribute-governs-test-transactions.{md,good.al,bad.al}

These articles already cite Microsoft Learn and were carefully
cross-referenced; the regeneration skips their topics rather than
duplicating them.

File counts after regeneration:

  performance   35 .md  (5 preserved + 30 new)
  privacy       17 .md
  security      18 .md  (1 preserved + 17 new)
  style         33 .md
  testing        1 .md  (preserved)
  ui            19 .md
  upgrade       18 .md

Total 141 atomic knowledge files, each strictly one rule. All pass
.github/scripts/validate_frontmatter.py with 0 errors and 0 warnings.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
2026-05-21 09:53:09 +02:00

31 lines
1.7 KiB
Markdown

---
bc-version: [all]
domain: upgrade
keywords: [enum, ordinal, additive, append, backward-compatible, breaking-change]
technologies: [al]
countries: [w1]
application-area: [all]
---
# Add new enum values only at the end
## Description
An AL `enum` is a fixed list of ordinal-named values. Persisted rows reference enum members by ordinal, not by name. The only enum mutation that preserves the meaning of every existing row is **appending a new value at the end** — every previously valid ordinal still maps to the same member. Inserting a new value in the middle, renumbering existing values, or removing a value without obsoletion all shift ordinals: rows written with the old layout silently take on the new member at their saved ordinal.
## Best Practice
When adding an enum value, place it after the last existing `value(N; ...)` entry, with an ordinal strictly greater than every existing one. Never renumber existing entries. To retire a value, do not delete it: mark it `ObsoleteState = Pending` (and later `Removed`) with `ObsoleteReason` and `ObsoleteTag` so the ordinal remains taken.
See sample: `enum-values-additive-at-end.good.al`.
## Anti Pattern
Inserting a value between existing entries ("just put `NewMiddleValue` between `First` and `Second`"), or removing a value from the enum without first going through `ObsoleteState = Pending``Removed`. Every row whose persisted ordinal matched the removed or shifted value now reads as a different member.
See sample: `enum-values-additive-at-end.bad.al`.
## See also
- `obsoletion-requires-reason-and-tag.md` — how to retire an enum member correctly.
- `obsolete-pending-to-removed-staging.md` — the `Pending → Removed` lifecycle.