bcquality/microsoft/skills/review/al-error-handling-review.md

---
kind: action-skill
id: al-error-handling-review
version: 1
title: AL error handling review
description: Reviews AL source changes against error-handling guidance from BCQuality.
inputs: [pr-diff, file-path, folder-path]
outputs: [findings-report]
bc-version: [all]
technologies: [al]
countries: [w1]
application-area: [all]
---

# AL error handling review

Reviews AL source changes against the `error-handling` knowledge domain in BCQuality and emits a findings report. This is a leaf action skill: it invokes no sub-skills. It is one of the skills composed by `al-code-review`.

An orchestrator invokes this skill with a `pr-diff`, `file-path`, or `folder-path`. The skill produces a single JSON document conforming to the DO output contract.

## Source

Use READ's **Bounded retrieval for review skills** workflow with `-Domain error-handling`. Consume every catalog page across enabled layers before applying this leaf's Relevance and Worklist; preserve each exact catalog path and open complete bodies only for exact paths selected by the Worklist. If the helper or prepared index is unavailable or invalid, use READ's explicit path-discovery and bounded native-read fallback.

## Relevance

Apply the frontmatter matching rules defined in READ (*Frontmatter matching semantics*) against the task context:

- `bc-version` — the target BC version from the PR branch's `app.json` or the orchestrator-supplied version. If unavailable, the dimension is `unknown`.
- `technologies` — `[al]`.
- `countries` — the countries declared in the consuming app's `app.json`. Default to the orchestrator's configured context; if absent, `unknown`.
- `application-area` — the union of application areas declared by the changed objects. Pass the actual set; do not substitute `[all]`. If the area cannot be determined from the changes, the dimension is `unknown`.

Discard files that are not applicable. Retain conditionally applicable files (any dimension `unknown`) only when the orchestrator's configuration permits them; findings derived from those files MUST have `confidence` no higher than `medium`, AND the finding's `message` MUST name the dimension or dimensions that were unknown.

## Worklist

Narrow the relevant files to the subset that applies to the changes under review. For each relevant file, compute overlap against:

- The changed AL object names and types — especially codeunits that post or validate, tables and table extensions with `OnValidate` triggers, and any procedure that raises errors or orchestrates a batch over records.
- The changed procedures and triggers, weighted toward `OnValidate`/`OnInsert`/`OnModify` triggers, posting and validation routines, and procedures attributed with `[ErrorBehavior(...)]` or `[TryFunction]`.
- Tokens extracted from the diff that relate to error surfacing and diagnostics (`Error`, `ErrorInfo`, `FieldError`, `TestField`, `Title`, `Message`, `DetailedMessage`, `AddAction`, `AddNavigationAction`, `RecordId`, `PageNo`, `ErrorBehavior`, `Collect`, `HasCollectedErrors`, `GetCollectedErrors`, `ClearCollectedErrors`, `ErrorType`, `Internal`, `Client`, `TryFunction`, `GetLastErrorText`, Boolean assignment).
- Resolve changed standalone call targets; when the target declaration has `[TryFunction]`, worklist the ignored-return rule even if the declaration itself is unchanged. Only assignment and conditional use activate try semantics.

A file enters the candidate worklist when its `keywords` intersect the extracted tokens or its topic (derived from the index entry's `path`, `title`, and `description`) matches a changed object type. Read an article's full file — its `## Best Practice` / `## Anti Pattern` bodies — only after it makes the worklist; candidate selection uses the index alone.

The following targeted checks cover every current `error-handling` article:

- `[ErrorBehavior(ErrorBehavior::Collect)]`, `ErrorInfo.Collectible`, `HasCollectedErrors`, `GetCollectedErrors`, or `ClearCollectedErrors` is added or changed, especially when errors are collected without later surfacing/clearing them — `collect-validation-errors-with-errorbehavior`.
- Developer-only invariant text is raised with default client visibility, or a user-actionable validation is hidden as `ErrorType::Internal` — `errortype-internal-vs-client-for-diagnostics`.
- `FieldError` receives a complete capitalized sentence, repeats the field caption/value, or ends the predicate with punctuation — `fielderror-default-message-logic`.
- An unguarded `FieldError` is used as though it performed a comparison, or `TestField` is forced onto a complex rule needing a tailored predicate — `fielderror-vs-testfield`.
- A resolved call target is marked `[TryFunction]` but the call is a standalone statement whose Boolean result is ignored — `ignored-tryfunction-return-disables-try-semantics`. This call-site rule supersedes the performance TryFunction article unless writes and rollback expectations are also visible.
- A plain `Error` represents a known actionable correction that can be expressed through `ErrorInfo` actions/navigation, or an `ErrorInfo` omits the context needed for that action — `prefer-errorinfo-for-actionable-errors`.

Once the candidate worklist is known, resolve layer-precedence conflicts per READ. Drop lower-precedence files whose normative guidance (`## Best Practice` or `## Anti Pattern`) directly contradicts a higher-precedence candidate, and record each dropped file in `suppressed` with `reason: "layer-precedence"`. Files that would have been candidates but are hidden because their layer is disabled in consumer configuration are recorded with `reason: "configuration"`. Files that never became candidates are NOT recorded in `suppressed`.

When the post-conflict worklist is empty because no applicable error-handling knowledge exists, or because configuration suppressed every candidate, emit `outcome: "no-knowledge"`. When the worklist is empty because no applicable error-handling knowledge matched the changes, emit `outcome: "completed"` with an empty `findings` array.

## Action

For each worklist entry, evaluate the diff against the file's `## Best Practice` and `## Anti Pattern` sections. Emit findings as follows:

- When the diff contains a clear match for an Anti Pattern, emit a finding with severity `major` or `blocker`, a message summarizing the anti-pattern, `location` pointing to the offending line or range, and a `references` entry pointing to the knowledge file. Use `blocker` only when the knowledge file states the anti-pattern violates a platform-level guarantee. When the file does not make such a claim, the ceiling is `major`.
- When the diff contains code that contradicts a Best Practice without being a full anti-pattern, emit `minor` with the same reference shape.
- Applicability alone is not a finding. Emit `info` only for a concrete, non-actionable observation the article explicitly defines; otherwise emit nothing when no violation is present.

Set `confidence` to:

- `high` when the detection is based on an unambiguous pattern match (identifier, syntax, object type).
- `medium` when detection relies on heuristics or when any frontmatter dimension was `unknown`.
- `low` when the finding is an advisory derived only from applicability.

After evaluating each worklist entry, also consider whether the diff exhibits an error-handling defect the agent recognises from its general AL knowledge that no knowledge file in the worklist covers. Such candidates are agent findings within this skill's domain — emit them with `references: []`, an `id` slug prefixed with `agent:`, `confidence` capped at `medium`, `severity` capped at `minor` (agent findings are advisory and non-gating), and a `message` that is self-contained (describing both the issue and a concrete recommendation, since there is no knowledge-file footer for the consumer to fall back on). Hold every candidate to the precision bar in `skills/do.md` (*Agent findings*): emit only a concrete, material error-handling defect a knowledgeable BC reviewer would agree is wrong — steelman it first and drop anything stylistic, speculative, dependent on code outside the diff, or merely a valid alternative; when in doubt, omit. The scope is strictly error handling; defects outside this domain belong to other leaves and MUST NOT be emitted here. Before emitting, check the worklist for a knowledge file that matches the candidate — if one exists, upgrade the candidate to a knowledge-backed finding instead. See `skills/do.md` for the full contract.

For every emitted finding, decide whether the fix is mechanical. A fix is mechanical when it is small, local, and unambiguous from the diff context (for example: replace a string-concatenated `Error` with a Label-backed call; mark an internal-only failure `ErrorType::Internal`; add a missing `DetailedMessage`). For mechanical findings, emit `findings[].suggested-code` with the literal replacement for the source lines indicated by `location`. The payload must be a verbatim replacement — no diff markers, no fences, no commentary — that the consumer can render as a one-click suggestion. When a `.good.al` companion exists and the diff context matches the `.bad.al` shape, adapt the `.good.al` replacement into `suggested-code`.

Omit `suggested-code` only when the appropriate fix depends on context the skill cannot determine, when multiple defensible replacements exist, or when the fix spans non-contiguous code. If a finding is mechanical-looking but you omit `suggested-code`, set `findings[].suggested-code-omission-reason` to a short explanation. See `skills/do.md` for the full contract.

Outcome selection:

- `completed` — the skill evaluated every worklist item; default when the skill finishes normally, including when the resulting `findings` array is empty.
- `no-knowledge` — no applicable error-handling knowledge survived Source, Relevance, configuration filtering, and conflict resolution. `findings` is empty.
- `not-applicable` — the task context lacks an AL dimension (no AL changes in the diff, or `technologies` filter rejected the task).
- `partial` — a time or token budget was hit before the worklist was exhausted. `summary.coverage` reflects the evaluated subset; `outcome-reason` explains the cause.
- `failed` — an unrecoverable error occurred. `outcome-reason` is required.

## Output

Output conforms to the DO output contract. Every finding this skill emits MUST set `findings[].domain` to `"Error Handling"`. A populated example:

```json
{
  "skill": { "id": "al-error-handling-review", "version": 1 },
  "outcome": "completed",
  "summary": {
    "counts": { "blocker": 0, "major": 1, "minor": 1, "info": 0 },
    "coverage": { "worklist-size": 2, "items-evaluated": 2 }
  },
  "findings": [
    {
      "id": "microsoft/knowledge/error-handling/prefer-errorinfo-for-actionable-errors.md",
      "severity": "major",
      "message": "A validation error names the maximum allowed quantity but raises a plain Error with no recommended action. Use an ErrorInfo with a Fix-it AddAction so the user can apply the known value.",
      "location": {
        "file": "src/Sales/SalesLine.TableExt.al",
        "line": 88,
        "range": { "start-line": 86, "end-line": 89 }
      },
      "references": [
        { "path": "microsoft/knowledge/error-handling/prefer-errorinfo-for-actionable-errors.md" }
      ],
      "confidence": "high",
      "domain": "Error Handling"
    },
    {
      "id": "microsoft/knowledge/error-handling/errortype-internal-vs-client-for-diagnostics.md",
      "severity": "minor",
      "message": "This 'unexpected state' failure is developer-facing but is raised with default Client visibility. Mark it ErrorType::Internal so the detail goes to telemetry and the user sees a generic message.",
      "location": {
        "file": "src/Ledger/PostingEngine.Codeunit.al",
        "line": 211
      },
      "references": [
        { "path": "microsoft/knowledge/error-handling/errortype-internal-vs-client-for-diagnostics.md" }
      ],
      "confidence": "medium",
      "domain": "Error Handling"
    }
  ],
  "suppressed": []
}
```

When no applicable error-handling knowledge is available, the report is:

```json
{
  "skill": { "id": "al-error-handling-review", "version": 1 },
  "outcome": "no-knowledge",
  "summary": {
    "counts": { "blocker": 0, "major": 0, "minor": 0, "info": 0 },
    "coverage": { "worklist-size": 0, "items-evaluated": 0 }
  },
  "findings": [],
  "suppressed": []
}
```