Use the new mypy daemon to speed up type-checking

[stlehmann]

Since mypy 0.6 there is a daemon included. So instead of running mypy as a command-line tool, one can run it as a long-running daemon (server) process and use a command-line client to send type-checking requests to the server. A speedup of 10x or more for large code bases seems possible. I think that would definetly be a large benefit for the speed of this Plugin. I would also gladly give a hand on implementation. Have a look at the daemon docu http://mypy.readthedocs.io/en/latest/mypy_daemon.html. It is still in beta state but already used in larger scale at Dropbox.

[FichteFoll]

Thanks for the reference. I remember reading about it a few releases ago (#14) but didn't find any info about it other than a small mention in the changelog.

From a quick look at that site, I can see a few problems, though. Notably:

1. It doesn't seem to support --shadow-file.
2. It doesn't support Windows. (that's not really a problem)

I would probably use the daemon behind a linter flag and have it disabled by default for the time being. The --timeout parameter is especially useful because we can not deinitialize the plugin when ST is closed. Not sure how to tackle the first problem without requesting support for it, though.

[FichteFoll]

Small update as the upstream issue I was subscribed to was closed.

Not sure it's worth investigating because I'll need to manage the daemon in the plugin code. As long as --incremental does its job well (read: fast) enough, I'll hold back working on this. There are other more important things to manage.

[LawrenceJGD]

Hello, I wanted to ask if there's going to be any work to implement dmypy soon, it would make it faster to use. Thanks

[kaste]

Yeah, I tried dmypy but it doesn't lint in the background (aka "while you type") and I hate it a bit when linters or feedback comes after saving only.