name: astro-components
description: Guidance and best practices for Astro components in Starlight projects. Use when building or editing .astro components: presentational vs wrapper components, props and TypeScript interfaces, slots, reusing Section/Grid/Card and Starlight Icon, styling with cascade layers, and keeping data separate from presentation so content collections and MDX integration stay clean.
Astro Components — Guidance and Best Practices
Apply this skill when implementing or refactoring Astro components so that data-driven sections (e.g. example factories, feature grids) are built with clear separation of data and presentation and consistent use of existing layout and iconography.
Component anatomy
Every .astro file has two parts:
- Frontmatter (script) — Between the first
--- and second ---. Runs at build time. Use for:
- Imports (e.g.
Icon from @astrojs/starlight/components, or project components)
- Destructuring
Astro.props and defining defaults
- TypeScript
interface Props { ... } for clear, type-safe props
- Template — HTML-like markup below the second
---. Use {expression} for JS, <slot /> for children, and set:html only for trusted content.
Rule: Do not use a leading _ for “private” members (e.g. internal variables); follow project convention and use normal names.
Presentational vs wrapper components
Presentational component
- Receives all data via props. Does not call
getCollection, getEntry, or fetch.
- Renders one “unit” (e.g. one factory card, one feature column). Reusable anywhere the same shape of data is available.
- Example:
ExampleFactorySection.astro with factory: { title, technologies, applicationStyle, skills, commands, agents, workflows }.
Wrapper component
- Calls
getCollection('collectionName') (or getEntry) in the frontmatter. Handles sort/filter.
- Renders a section (e.g.
<Section>) and maps over entries, rendering the presentational component for each with entry.data.
- Example:
ExampleFactoriesList.astro that does getCollection('exampleFactories') and maps to <ExampleFactorySection factory={entry.data} />.
Why: MDX runs in a context where async getCollection in the template is awkward. Keeping data-fetch in an Astro wrapper and passing entry.data into a presentational component keeps MDX simple (import and render one wrapper) and makes the presentational component testable and reusable.
Props and TypeScript
- Define an
interface Props in the frontmatter. Destructure with defaults when appropriate: const { title, size = "large" } = Astro.props;
- For “one entry” components, accept a single object prop (e.g.
factory) whose shape matches the content collection schema so the wrapper can pass entry.data directly.
Reusing layout and iconography
Section: Use <Section title="…" description="…"> from ~/components/Section.astro for consistent section title and description. The title prop can include HTML (e.g. <span class="light-text">…</span>); use set:html in the component as in existing usage.
Grid: Use <Grid columns={4}> from ~/components/user-components/Grid.astro. Pass the desired column count; children are laid out in a responsive grid. Use for four-column layouts that mirror the “Key components” cards.
Icons (Starlight): Import Icon from @astrojs/starlight/components. Use <Icon name="…" color="…" size="…" />. For the Skills/Commands/Agents/Workflows four-column layout, use the same icon names and colors as the Key components section — see the astro-starlight skill for the canonical table.
Card-style blocks: For a column that shows an icon, heading, and list (e.g. Skills + list of skill ids), reuse the same icon and color as NewCard.astro. You can use a smaller or simplified card layout (e.g. icon + heading + <ul> of items) without the arrow. Keep visual consistency with the existing cards.
Slots
- Default slot:
<slot /> renders the component’s children. Use for a single block of content (e.g. card body, section body).
- Named slots:
<slot name="footer" /> in the component; at the call site use <Fragment slot="footer">…</Fragment>. Use when the component has two or more distinct content areas.
For list/card components that only need a single content area, the default slot is usually enough. For Section, the default slot is the section body.
Styling
- Cascade layers: Use
@layer starlight.components { ... } for component-specific overrides so styles integrate with Starlight’s theme and don’t fight the default cascade.
- Scoped styles: Styles in a
<style> block in an Astro component are scoped to that component by default. Use :global(...) only when you need to target child components or Starlight internals.
- Layout: Prefer the existing Grid and Section for spacing and structure; add minimal custom CSS for the new component’s internals (e.g. list spacing under each column heading).
Checklist for new presentational components
Checklist for wrapper components
Project references
For the full workflow (collection + data files + presentational component + wrapper + MDX), use the astro-starlight skill together with this one.
