Thread by @lzsthw

Finished this morning's Nim hacking and, well, it has async IO but it's rough as hell. Pretty much nothing is done for you, so it's a lot like JavaScript before async/await, but weirdly it has the await keyword. Some issues with this:

1. I'm not sure why the {.async.} pragma doesn't also setup that function to return Future[T]. It's kind of pointless if all that I get is the await keyword, and then every function I want to wait on has to be hand coded futures. Maybe the docs are just wrong?

2. I'm guessing this is more nanomsg's fault than Nim asyncdispatch, but the whole pollfd, addWrite/addRead system doesn't work on the send. I'll register addWrite, the pollfd will say it's ready, then the nanomsg send actually blocks, which...should be impossible.

3. Everyone wants to own the IO, but nobody gets it right. Nanomsg wants to be in charge, but gives you the pollfd through a complicated getsockopt, and then the pollfd doesn't work. Nim wants you to NOT use addWrite/addRead because of Windows, so...use only Nim? Nanomsg?

4. You'll notice I create an addRead and addWrite, but actually that's not correct. I'm only doing this because the backend will actually serialize these, but with this setup I could read and write totally out of order since they just go when the event happens. Why did I do it?

5. Again, writing these Futures is brutal. If want to have a send then a recv (which is probably 95% of all IO) I have to write the sendCommand to run, then *it* does addRead after the send to chain the future. Now we're back to callback hell from JavaScript.

6. My expectation in an Async IO system is I say "this thing is async IO", then I just do read/write like normal and it figures it out for me. No futures, no callbacks, no await, just automatic IO concurrency. You could probably build on asyncdispatch to do it.

7. Finally, Nanomsg has a serious issue if the pollfd it gives me doesn't actually work. This was the exact same problem with ZeroMQ, where they wanted to be the IO KING and all the code was written as if I'm not a professional who knows how to do my IO better.