Loose comments from editor (emacs) perspective

[gracjan]

Loose comments from editor (emacs) perspective:

1. Buffers (open files) can be not yet saved and therefore differ from what is on disk currently. Generally we want to operate with the visible contents.
2. Files-while-editing have the tendency to by not-valid Haskell. Or at least no type correct. There were multiple issues raised so that haskell-mode works with somewhat valid Haskell instead of totally not working.
3. Editors have cursor position that can serve as indicator what to act on.
4. Editors have marked region that can serve as indicator what to act on.
5. Smooth interaction requires latency hiding because 200ms is when people start to notice non-smoothness. Editor needs to be ready to handle longer-running queries, actually any query can run 'too long'. This means communication needs to be asynchronous.

[alanz]

Great to get this input. Some comments

1. ghc-mod has a map-file mechanism whereby the unsaved buffer is transferred to the backend for error checking or other processing.
2. invalid files are a problem, but I think being able to bring the full power of the GHC parser and/or the approach taken in Yi (originally) or http://blog.haskell-exists.com/yuras/posts/incremental-lexer.html will help.
3. The editor context should definitely be available to plugins. How precisely to communicate available commands/features from a plugin to an editor is something we still need to get to grips with.
4. Same as 3
5. The session needs to run locally, and be fast. Hopefully this can be achieved by splitting out the comms into multiple logical channels (possibly all multiplexed onto a single one for emacs) and ensuring that the backend is always "live" in the sense of responding on channels not explicitly marked as possibly blocking.

[gracjan]

I think I got my point across so we can close this issue.