`SlackListsItem FieldMessage.message` type does not match API response shape

Package

@slack/types

SDK Version

@slack/types 2.21.1

Node.js Version

v24.12.0

Operating System

No response

Steps to Reproduce

SlackListsItemFieldMessage in packages/web-api/src/types/request/slackLists.ts defines:

export interface SlackListsItemFieldMessage {
  column_id: string;
  message: string[];
}

The Slack API can return the message field as either:

• A single message object: "message": {"text":"hello", "ts": "123.456"}
• An array of message objects: "message":[{"text": "a"}, {"text":"b"}]

The current typing is inaccurate in two ways:

1. It assumes message is always an array, but the API may return a single object
2. It types elements as string when they areactually message objects

See java-slack-sdk#1587 for the same API inconsistency on the Java side.

Suggested fix

interface SlackListsItemMessage {
    text?: string;
    ts?: string;
    user?: string;
    team?: string;
    type?: string;
}

export interface SlackListsItemFieldMessage {
    column_id: string;
    message: SlackListsItemMessage | SlackListsItemMessage[];
  }


export interface SlackListsItemFieldMessage {
    column_id: string;
    message: SlackListsItemMessage | SlackListsItemMessage[];
}

This types it as a union so consumers handle both shapes.

Impact

No runtime crash (JavaScript is untyped at runtime), but developers relying on the type will write incorrect code, like calling .map() on a non-array or treating objects as strings.

References

• slackapi/java-slack-sdk#1587
• https://docs.slack.dev/reference/methods/slackLists.items.create#field-types

Expected Result

N/A

Actual Result

N/A

Start in packages/web-api/src/types/request/slackLists.ts and compare SlackListsItemFieldMessage with the response shapes described in the issue and the Slack API field-types documentation. Done means the TypeScript definition accurately represents message as either a message object or an array of message objects, including the fields shown.