web/.agents/skills/vercel-composition-patterns/rules/patterns-explicit-variants.md
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):
// What does this component actually render?
<Composer
isThread
isEditing={false}
channelId='abc'
showAttachments
showFormatting={false}
/>
Correct (explicit variants):
// 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:
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:
No boolean prop combinations to reason about. No impossible states.