opencode-agent-kit/template/.opencode/skills/vercel-composition-patterns/rules/patterns-explicit-variants.md

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---
title: Create Explicit Component Variants
impact: MEDIUM
impactDescription: self-documenting code, no hidden conditionals
tags: composition, variants, architecture
---

## Create Explicit Component Variants

Instead of one component with many boolean props, create explicit variant
components. Each variant composes the pieces it needs. The code documents
itself.

**Incorrect (one component, many modes):**

```tsx
// What does this component actually render?
<Composer
  isThread
  isEditing={false}
  channelId='abc'
  showAttachments
  showFormatting={false}
/>
```

**Correct (explicit variants):**

```tsx
// Immediately clear what this renders
<ThreadComposer channelId="abc" />

// Or
<EditMessageComposer messageId="xyz" />

// Or
<ForwardMessageComposer messageId="123" />
```

Each implementation is unique, explicit and self-contained. Yet they can each
use shared parts.

**Implementation:**

```tsx
function ThreadComposer({ channelId }: { channelId: string }) {
  return (
    <ThreadProvider channelId={channelId}>
      <Composer.Frame>
        <Composer.Input />
        <AlsoSendToChannelField channelId={channelId} />
        <Composer.Footer>
          <Composer.Formatting />
          <Composer.Emojis />
          <Composer.Submit />
        </Composer.Footer>
      </Composer.Frame>
    </ThreadProvider>
  )
}

function EditMessageComposer({ messageId }: { messageId: string }) {
  return (
    <EditMessageProvider messageId={messageId}>
      <Composer.Frame>
        <Composer.Input />
        <Composer.Footer>
          <Composer.Formatting />
          <Composer.Emojis />
          <Composer.CancelEdit />
          <Composer.SaveEdit />
        </Composer.Footer>
      </Composer.Frame>
    </EditMessageProvider>
  )
}

function ForwardMessageComposer({ messageId }: { messageId: string }) {
  return (
    <ForwardMessageProvider messageId={messageId}>
      <Composer.Frame>
        <Composer.Input placeholder="Add a message, if you'd like." />
        <Composer.Footer>
          <Composer.Formatting />
          <Composer.Emojis />
          <Composer.Mentions />
        </Composer.Footer>
      </Composer.Frame>
    </ForwardMessageProvider>
  )
}
```

Each variant is explicit about:

- What provider/state it uses
- What UI elements it includes
- What actions are available

No boolean prop combinations to reason about. No impossible states.