Warning about inviting unknown users is not shown when creating a room via "Start chat"

[anoadragon453]

Steps to reproduce

1. Click the + "Start chat" button next to the header of the People section of the room list.
2. Attempt to start a chat with a user that you know does not exist (and alternatively, on a homeserver you know does exist).
3. Click "Go"
4. You are let through to the next stage without any warnings.
5. Send a message to create the room.

If you chose a non-existent localpart on a real matrix homeserver domain, then that non-existent user will have an invite (which the homeserver received). If a user is ever created under that localpart, then they will find that invite waiting for them when they log in for the first time.

If you chose a non-existent homeserver domain, then you will end up in a broken room.

Outcome

What did you expect?

The following errors appear when attempting to invite a non-existent user through the "Invite" dialog in an existing Matrix room.

When attempting to invite a non-existent localpart on an existing homeserver:

When attempting to invite any user on a non-existent homeserver:

What happened instead?

For a non-existent user on an existing homeserver, no warning is presented on clicking Go here:

When attempting to contact a user on a non-existent homeserver, you end up with a broken room. Clicking retry does nothing:

To actually leave these rooms, user have to search for "Empty room" in their list of rooms and select it. This will take them to the same room, but with a composer that is usable. They can then leave the room from there.

Operating system

NixOS

Application version

Element version: 1.11.24 Olm version: 3.2.12

How did you install the app?

nixpkgs package repository

Homeserver

No response

Will you send logs?

No

[t3chguy]

This looks like the create-dm-on-first-message flow caused a regression

[weeman1337]

Not sure if this is really a regression. Recording from pre-start-dm-on-first-message version:

[weeman1337]

I do not get the error when sending the message, otherwise behaves the same as pre-create-dm-on-first-message.

[weeman1337]

@anoadragon453 can you send logs right after „Some of your messages have not been sent“ happened?

[anoadragon453]

@weeman1337 to encounter the broken room, you need to attempt to invite a user from a homeserver that will not respond to an invite over federation. In your example you're using matrix.org, which will.

I suggest also just typing random characters for the domain name of the user you're trying to invite, such as @hdsajkhkjahsduow4huhuisa:asdhjkasdghasduauahsud.com.

[anoadragon453]

In the case of the homeserver that does exist (your first gif), I expect to still receive a warning that the user does not exist (a /profile lookup for them failed). We have such a warning when inviting a user to an existing room:

[giomfo]

We should consider to implement client side this MSC3720: Account status endpoint. This would ease the handling of these use cases

[anoadragon453]

@giomfo It may have been an intentional design decision for GET /_matrix/client/v3/profile/{userId} to return a 404 if you don't share a room with that user, as it allows users to hide the fact that they exist from certain other users. In this world, having a warning like the one above about the user might not existing is the best we can do.

MSC3720 as written today would compromise that privacy benefit (though we can have a discussion in spec land about whether we'd want to do that to improve functionality/allow users to explicitly choose their preference).

Today, the warning should exist in all cases where you attempt to invite a user to a chat, and currently it does not for the Start Chat flow.