Using Lightning Base Components

Lightning Base Components (LBC) are the lightning-* web components shipped by Salesforce. This skill routes an agent through the right decision sequence so the final component choice is as specific as possible and backed by real API docs — not a hand-rolled reimplementation of something that already exists.

When to Use This Skill

• User describes a UI need ("searchable dropdown", "record edit form", "modal with footer") and asks which lightning-* component fits.
• User is about to build a primitive (button group, combobox, toast) and should be using LBC instead.
• User asks you to review LWC markup for LBC-related issues — specifically overriding SLDS classes or restyling LBC internals.
• User needs the authoritative props/events/slots for a specific lightning-* tag.

Prerequisites

• Knowledge of which LBC namespace your org uses (lightning is the default public namespace; some platforms expose lightning-community or others — the user's meta files will clarify).
• The skill ships authoritative API docs for every Lightning Base Component in references/lightning-components.md. Each component is a # Component API Structure block; grep for **Name:** <camelCaseName> (e.g. **Name:** datatable) to jump to its Properties / Methods / Events / Slots. Read this rather than relying on cached knowledge — LBC evolves and the reference is the source of truth.

Workflow

Step 1 — Read the entire component index first

Open lightning-component-index.md and scan all entries before making any selection. This is non-negotiable: LBC's value comes from picking the most specialized component, and skipping the scan leads to reinventing compound widgets out of primitives.

As you scan, compile a candidate list — every component whose description touches any aspect of the use case. Do not filter or rank yet.

Step 2 — Narrow to the most specific fit per feature

Once the scan is complete:

• For each feature in the use case, select the most specific component that covers it. Prefer a specialized compound (lightning-record-form, lightning-tabset, lightning-datatable) over a generic primitive (lightning-input, lightning-button) when the specialized one covers the scenario end-to-end.
• Avoid duplication: if lightning-record-form already renders fields for a record, do not pair it with lightning-input-field unless you're explicitly overriding behavior.

Step 3 — Share the shortlist and confirm

Present the final shortlist to the developer with a one-line rationale per component. Wait for explicit confirmation before pulling full API docs. This prevents the agent from burning context on components the developer has already mentally ruled out.

Step 4 — Retrieve full API docs

Once confirmed, use the bundled helper to pull the exact API blocks — this avoids ad-hoc grepping across a large reference:

scripts/extract-component-docs.sh <camelCaseName> [<camelCaseName>...]

Convert lightning-<foo> tags to camelCase (no lightning- prefix):

• lightning-datatable → datatable
• lightning-record-edit-form → recordEditForm
• lightning-button-icon → buttonIcon

Each returned block has the same shape: Basic Information (tag, namespace, type), Properties (name, type, default, description), Methods, Events, Slots, and (where applicable) usage notes. This skill is about picking the components; the bundled reference is about wiring them.

Step 5 — Produce integration guidance

Using the per-component reference, walk the developer through:

• The exact <lightning-...> tag and required attributes.
• Which events to bind (onchange, oncommit, onsuccess, …) and what the event payload contains.
• Any slots to fill (headers, footers, custom content).
• Known constraints from the component docs (e.g. lightning-record-form requires object-api-name and record-id for edit/view modes).

Step 6 — Respect LBC styling rules

Do not override SLDS classes on LBC internals. See lbc-expert-guidance.md for specifics. Common issues:

• Targeting .slds-button or .slds-input in the host component's CSS to restyle an LBC — LBC ships inside a shadow root, so these selectors either leak into sibling components or get stripped entirely. Use the component's documented styling hooks (--sds-c-button-*, etc.) instead.
• Wrapping an LBC just to mutate its internal markup. You can't — the markup is hidden behind the shadow root. If the component doesn't expose the slot/prop you need, that's a platform-level gap, not a restyling job.

Examples

Example — "I need a multi-select combobox with typeahead"

1. Scan the component index end-to-end.
2. Candidate list includes: lightning-combobox, lightning-dual-listbox, lightning-record-picker.
3. Shortlist: lightning-dual-listbox (the documented multi-select base component). Rule out lightning-combobox — its documented API is single-select; it has no type="multi" and no multi-select mode. Flag that lightning-record-picker only fits if the values are record IDs.
4. Developer confirms lightning-dual-listbox.
5. Run scripts/extract-component-docs.sh dualListbox.
6. Return the options, value, onchange payload, and required label props from the block's Properties / Events sections.

Example — "I'm going to write my own modal"

1. Scan finds lightning-modal, lightning-modal-body, lightning-modal-footer, lightning-modal-header.
2. Shortlist is the 4 modal components.
3. Confirm.
4. Run scripts/extract-component-docs.sh modal modalHeader modalBody modalFooter → full modal API (how to extend LightningModal, the static .open() pattern, slotting the header/body/footer).
5. Steer the developer away from rolling their own dialog.

Verification Checklist

• The full component index was scanned before any selection (no keyword-search shortcutting).
• Candidate list included every component that touches the use case.
• Final shortlist selects the most specific component per feature.
• Developer confirmed the shortlist before the bundled component reference was opened.
• Integration guidance cites props / events / slots from the real API docs (not inferred).
• No suggestions to restyle LBC by overriding SLDS classes.

Troubleshooting

• Grep for **Name:** <name> returns no match — name is wrong, or the reference uses a different camelCase. Double-check against the component index (lightning-record-form → recordForm, lightning-record-view-form → recordViewForm, lightning-button-icon → buttonIcon).
• Proposed component doesn't have the prop you expected — trust the real API doc over memory. LBC evolves; cached knowledge lies.
• Developer resists the shortlist — don't skip Step 4. Still retrieve the docs for the developer's preferred choice so they see the actual trade-offs.
• Developer wants to restyle LBC internals — redirect to styling hooks (see the LBC Expert reference). Refusing shadow DOM penetration is the correct answer.