TL;DR: Until a few hours ago, the SDK function conversations_invite() used to succeed with no issues. Now, it fails with error: no_user. It seems that the users argument to the conversations.invite API method may have changed to require a JSON array (rather than a comma-separated string), so conversations_invite() may need to be updated accordingly. CC: @tracertea

Reproducible in:

The Slack SDK version

$ pip freeze | grep slack
slack-bolt==1.6.1
slack-sdk==3.7.0

Python runtime version

$ python --version
Python 3.9.5

OS info

$ sw_vers && uname -v
ProductName:    macOS
ProductVersion: 11.2.3
BuildVersion:   20D91
Darwin Kernel Version 20.3.0: Thu Jan 21 00:07:06 PST 2021; root:xnu-7195.81.3~1/RELEASE_X86_64

Steps to reproduce:

Attempt to invite a user to a channel via conversations_invite(), passing the following arguments:

• channel (str): The channel ID
• users (str or list): A list of user IDs to invite

Note that if conversations_invite() is passed users as a list (i.e., rather than str—both types are indicated to be valid), it will collapse that list into a comma-separated str, which is consistent with Slack's API documentation for the conversations.invite method's users argument:

A comma separated list of user IDs. Example:
W1234567890,U2345678901,U3456789012

Surprisingly, this will fail:

channel = 'C1234567890'
users = ['U2345678901']

client.conversations_invite(channel=channel, users=users)
# "ok": false, "error": "no_user"

However, if we instead bypass conversations_invite() and directly call the conversations.invite method so that users is not collapsed into a comma-separated str and is passed directly as a list, the call succeeds:

channel = 'C1234567890'
users = ['U2345678901']

client.api_call(
    "conversations.invite",
    json={"channel": channel, "users": users},
)
# "ok": true

Expected result:

Expected a successful response from the conversations.invite API method:

{
  "ok": true,
  "channel": {
    "id": "[REDACTED]",
    "name": "[REDACTED]",
    "is_channel": true,
    "is_group": false,
    "is_im": false,
    "created": ["REDACTED"],
    "is_archived": false,
    "is_general": false,
    "unlinked": 0,
    "name_normalized": "[REDACTED]",
    "is_shared": false,
    "parent_conversation": null,
    "creator": "[REDACTED]",
    "is_ext_shared": false,
    "is_org_shared": false,
    "shared_team_ids": [
      "[REDACTED]"
    ],
    "pending_shared": [],
    "pending_connected_team_ids": [],
    "is_pending_ext_shared": false,
    "is_member": true,
    "is_private": true,
    "is_mpim": false,
    "last_read": "[REDACTED]",
    "is_open": true,
    "topic": {
      "value": "",
      "creator": "",
      "last_set": 0
    },
    "purpose": {
      "value": "",
      "creator": "",
      "last_set": 0
    }
  }
}

Actual result:

We get an error indicating that "No value was passed for users":

{
  "ok": false,
  "error": "no_user"
}