al-coding-standards

AL Coding Standards

Use this skill when implementing or reviewing AL code.

This skill is a quick reference. The canonical rules source for AL files in the workspace overlay is templates/vscode-workspace/.github/instructions/al.instructions.md.

Naming rules

• Use PascalCase identifiers and avoid underscores, hyphens, and prefix-style affixes.
• Use spaces as word separators in AL object and field names; do not use underscores or camelCase for display names.
• Keep all object and field names to a maximum of 30 characters.
• Let the namespace carry the project affix; do not duplicate it in object names.
• Keep internal suffixes out of captions, labels, tooltips, and translated user-facing text.

Affix rules

• In table extensions, use suffix affixes on added fields; in custom tables, avoid unnecessary affixes.
• Never use prefix affixes.

Extension patterns

• Use Rec.FieldName bindings in page extensions.
• Use addlast or addfirst only; do not use addafter or addbefore.
• Use appropriate ApplicationArea for new fields in page extensions, typically All.
• Use modify("Field Name") to add triggers to existing fields in table extensions.

Method and data rules

• Use PascalCase method calls such as Insert, Modify, and Delete.
• Use DataClassification = CustomerContent for customer data fields unless a more specific classification is required.
• Use clear error messages with meaningful field or business context.
• Extract repeated business logic into shared procedures or codeunits.

Event subscribers

• Place subscribers in a dedicated codeunit named "[SourceObjectName] EH [PROJECTSUFFIX]".
• Set SingleInstance = true on event subscriber codeunits.
• Write EventName without quotes in subscriber attributes.

Permission sets

• Use AL permissionset objects, not XML.
• Convention: *_E* (Edit/IMD), *_R* (Read), *_X* (Execute).

Labels and enums

• Add a Comment to labels with placeholders explaining each placeholder.
• Use CopyStr only when lengths differ; use MaxStrLen(destination) for truncation.
• For enum type mismatches, use Enum::TargetEnum.FromInteger(SourceEnum.AsInteger()).

File organization

• Add new objects to the appropriate folder based on object type.

When to apply

• AL implementation
• AL code review
• design review when object naming and placement decisions matter