`subteam_members_changed` Message Results In A `EventTypeErrorBadMessage` Event

Apr 22, 2025 by ADMIN 80 views

**Resolving the `subteam_members_changed` Message Issue in Socketmode**

What happened

When receiving a message in socketmode for subteam_members_changed, it results in a EventTypeErrorBadMessage EventType with an empty cause field. This unexpected behavior occurs due to an issue unmarshalling the inner event.

Expected behavior

The expected behavior is to receive a SubteamMembersChangedEvent event. However, the current implementation fails to achieve this, leading to a EventTypeErrorBadMessage event.

Steps to reproduce

To reproduce this issue, follow these steps:

Create a socketmode client.
Attempt to process a EventTypeEventsAPI message in response to subteam_members_changed.

The underlying error

The underlying error lies in the unmarshalling of the inner event. Specifically, the error message cannot unmarshal number into Go struct field SubteamMembersChangedEvent.added_users_count of type string indicates that the added_users_count field is being unmarshalled as a string instead of an integer.

Reproducible code

The following code snippet demonstrates the issue:

func (e *EventHandler) Run(ctx context.Context) error {
	log := logger.Sugar()

	errg, ctx := errgroup.WithContext(ctx)
	errg.Go(func() error {
		for evt := range e.socket.Events {
			// log.Debugw("event", "event", evt)
			switch evt.Type {
			case socketmode.EventTypeEventsAPI:
				e.handleEventsAPIEvent(ctx, &evt, e.socket)
			case socketmode.EventTypeErrorBadMessage:
				// THIS WILL CATCH THE MESSAGE
				log.Debugw("bad message", "event", evt)
			default:
				log.Debugw("unsupported event type", "event", evt)
			}
		}
		return nil
	})
	errg.Go(func() error {
		err := e.socket.RunContext(ctx)
		if err != nil {
			log.Errorw("socket run failed", "error", err)
		}
		return err
	})
	return errg.Wait()
}

Manifest.yaml

The following versions are affected by this issue:

Go: 1.24
slack-go/slack: 0.15.0, 0.16.0, 0.17.0-rc2 (and likely more)

Proposed fix

To resolve this issue, update the SubteamMembersChangedEvent struct to utilize an int instead of a string type for the added_users_count and removed_users_count fields. The updated struct should resemble the following:

type SubteamMembersChangedEvent struct {
	Type               string   `json:"type"`
	SubteamID          string   `json:"subteam_id"`
	TeamID             string   `json:"team_id"`
	DatePreviousUpdate int      `json:"date_previous_update"`
	DateUpdate         int64    `json:"date_update"`
	AddedUsers         []string `json:"added_users"`
	AddedUsersCount    int   `json:"added_users_count"`
	RemovedUsers       []string `json:"removed_users"`
	RemovedUsersCount  int   `json:"removed_users_count"`
}

Q: What is the `subteam_members_changed` message in Socketmode?

A: The subteam_members_changed message is an event sent by Slack to indicate that the membership of a subteam has changed. This event is part of the Socketmode API, which allows developers to receive real-time updates from Slack.

Q: What is the expected behavior when receiving the `subteam_members_changed` message?

A: The expected behavior is to receive a SubteamMembersChangedEvent event, which contains information about the subteam membership change, such as the added and removed users.

Q: What is the issue with the current implementation?

A: The current implementation fails to correctly unmarshal the SubteamMembersChangedEvent event, resulting in a EventTypeErrorBadMessage event with an empty cause field. This is due to the added_users_count and removed_users_count fields being unmarshalled as strings instead of integers.

Q: How can I reproduce the issue?

A: To reproduce the issue, create a socketmode client and attempt to process a EventTypeEventsAPI message in response to subteam_members_changed.

Q: What is the proposed fix for the issue?

A: The proposed fix is to update the SubteamMembersChangedEvent struct to utilize an int instead of a string type for the added_users_count and removed_users_count fields.

Q: Why is the `added_users_count` and `removed_users_count` fields being unmarshalled as strings?

A: The added_users_count and removed_users_count fields are being unmarshalled as strings because the SubteamMembersChangedEvent struct is defined with these fields as string types. This is causing the unmarshalling process to fail, resulting in the EventTypeErrorBadMessage event.

Q: How can I update the `SubteamMembersChangedEvent` struct to fix the issue?

A: To update the SubteamMembersChangedEvent struct, change the type of the added_users_count and removed_users_count fields from string to int. This will ensure that these fields are correctly unmarshalled as integers, resolving the EventTypeErrorBadMessage event issue.

Q: What are the affected versions of the Slack Go library?

A: The affected versions of the Slack Go library are:

Go: 1.24
slack-go/slack: 0.15.0, 0.16.0, 0.17.0-rc2 (and likely more)

Q: How can I verify that the issue is fixed?

A: To verify that the issue is fixed, update the SubteamMembersChangedEvent struct to utilize an int instead of a string type for the added_users_count and removed_users_count fields. Then, attempt to process a EventTypeEventsAPI message in response to subteam_members_changed using a socketmode client. If the issue is fixed, you should receive a SubteamMembersChangedEvent event with the correct information.