Responses

A handler answers by returning a value:

Return	Discord shows
a string	a message with that text
JSX (<Container>..</Container>)	a Components V2 message, checked against Discord's limits
c.ephemeral(x) / Ephemeral(x)	x, visible only to the user who invoked it
a <Modal>	the modal, opened
c.defer(..)	a loading state, then the result (Deferring)
from a click: markup	the clicked message, updated (Handlers)
from a click: c.reply(x)	a new message instead
a raw InteractionResponse	exactly that, as an escape hatch

export const secret = command({
  name: "secret",
  description: "Only you can see this",
  handler: (c) =>
    c.ephemeral(
      <Container accentColor={0x5865f2}>
        <Text>## The answer is {6 * 7}</Text>
      </Container>,
    ),
})

Message settings

A View is the whole message. Wrap it in <Message> for message-level settings:

export const announce = command({
  name: "announce",
  description: "Announce quietly",
  handler: (c) => (
    <Message suppressNotifications allowedMentions={{ parse: [] }}>
      <Text>Release notes are out, {`<@${c.user.id}>`}</Text>
    </Message>
  ),
})

Files

upload(name, data) attaches a file. Pass it as the src of <File>, <Thumbnail> or <Item>, and it is sent with the message and referenced as attachment://<name>:

export const report = command({
  name: "export",
  description: "Export as CSV",
  handler: () => (
    <>
      <Text>Your export</Text>
      <File src={upload("export.csv", "name,score\nAda,7", { contentType: "text/csv" })} />
    </>
  ),
})

Answers with files go through Discord's callback endpoint and the HTTP request is answered with 202; composurejs does this for you.

Errors

throw new UserError("..") shows that message to the user, ephemeral. Any other error is logged, with its cause chain, and the user sees "Something went wrong.". To customize what users see, set an Error Renderer. It also handles failures in deferred work:

export const app = new App().onError((error, c) =>
  error instanceof UserError ? <Text>⚠️ {error.message}</Text> : <Text>Something broke. We've been told.</Text>,
)

Its output is always ephemeral. At most one App in a tree may set onError.