message_edit: Fix local echo of message edit.

[roanster007]

Previously, when a message is edited, it is locally echoed with its
pre-edit content.

This is because previously, when we tried to render the edited
message of the edit box during local echo, in order to update
the content, flags, and is_me_message properties of the message
object with that of those returned is markdown.render(), we used
the spread operator and created a new message object, and updated
the existing message object with this new one.

This was misconverted, since edit_locally() method already has a
fully-rendered message object to start with, and is just doing a
rerendering, it should be mutating what message it received, rather
than constructing a new local variable.

CZO

Screenshots and screen captures:

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[timabbott]

I think we need to be careful with mutating the core message object here; this may persist more than we'd expect. I'm not sure what the right strategy is, but I think it's pretty likely that if the edit operation fails, this doesn't get undone.

[roanster007]

I think it won't be much of a problem. If the patch request for save_message_row_edit fails, we can see that the original content is being restored, and the message_container is being re-rendered here, with original content and message_content_edited being set to false.

Manually testing by stopping the server and editing, it didn't seem like a problem either.

[roanster007]

I'm sure this isn't the right fix for this. I guess I'll give it another try to fix it.

[alya]

@timabbott Marking for integration review since you seem to be looking at this one, and there's a response to your comment above.

[roanster007]

@timabbott this bug still persists. approach is described here

[timabbott]

Great, merged, thanks @roanster007! Probably copying the most important part of the chat.zulip.org thread would have helped me review this more quickly; it took me a while to understand.