Automatic presence re-enter after network connection is back does not work

[KacperKluka]

We've discovered that a channel's presence is not automatically re-entered once you lose an internet connection and then it comes back on. After some further investigation, it turns out that this feature was working on older versions of ably-java SDK but it stopped working since version 1.2.2. Looking at the release notes of version 1.2.2 the most likely cause of this issue is the "Bump protocol version to 1.2".

Steps to reproduce:

• Create an AblyReatlime instance
• Join a channel's presence
• Verify that the client has joined the channel's presence (e.g. with the Ably dev dashboard)
• Turn the internet connection off
• Wait for the automatic "leave" event on the channel's presence
• Turn the internet connection on
• Wait for the automatic "enter" event

What should happen: The client should automatically re-enter the channel's presence after a few seconds
What happens: The client never re-enters the channel's presence

[sync-by-unito]

➤ Automation for Jira commented:

The link to the corresponding Jira issue is https://ably.atlassian.net/browse/SDK-2963

[paddybyers]

The relevant requirement is https://sdk.ably.com/builds/ably/specification/main/features/#RTP17c.

There is no test for this requirement, and no mention of this spec item in any historical PR.

There are two existing tests that mention RTP17:

• https://github.com/ably/ably-java/blob/main/lib/src/test/java/io/ably/lib/test/realtime/RealtimePresenceTest.java#L2095
• https://github.com/ably/ably-java/blob/main/lib/src/test/java/io/ably/lib/test/realtime/RealtimePresenceTest.java#L2767

Neither tests RTP17c specifically, and both are currently ignored.

[QuintinWillison]

@KacperKluka tried our version 1.2.19 release in AAT and has discovered that this issue is still not fixed. In further discussion with @paddybyers and @SimonWoolf in this Slack thread (internal) we have discovered that we should have reverted to protocol 1.0, not 1.1 as was the fix attempted in #858:

serverside, hasClientsidePresenceAutoReEnter is assumed to be true for >= 1.1 for most client libs, or >= 0.9 for js

I am therefore reopening this issue and another PR will be inbound shortly.