support for async on_transition() and on_dispatch()

[andrew-otiv]

We just tried to make all the methods of our state machine async. For on transition we hit:

  --> bazel-out/k8-fastbuild/bin/otiv3/pipeline_manager_process/state_machines/state_machine.rs:87:21
   |
87 |     on_transition = "Self::on_transition",
   |                     ^^^^^^^^^^^^^^^^^^^^^ expected fn pointer, found fn item
   |
   = note: expected fn pointer `for<'a, 'b, 'c> fn(&'a mut StateMachineStruct<_>, &'b State, &'c State) -> ()`
                 found fn item `for<'a, 'b, 'c> fn(&'a mut StateMachineStruct<_>, &'b State, &'c State) -> impl Future<Output = ()> {StateMachineStruct::<Handler>::on_transition}`

We get a similar error for on_dispatch. These methods aren't used in your async example. Are they just not supported yet?

Thanks!

[andrew-otiv]

ON_DISPATCH and ON_TRANSITION in the trait IntoStateMachine are non-async.

Thus, the issue isn't just in the macro.

[andrew-otiv]

Draft PR: #29

Draft because at the moment we haven't run the test suite yet.

[mdeloof]

Hi, I've been working on merging the no_std_async branch and there I've made the callback hooks async. on_dispatch and on_transition have been renamed to before_dispatch and after_transition respectively, and two new hooks - after_dispatch and after_transition - have been added.

Feel free to try it out and let me know if you encounter any issues. :)

[mdeloof]

This has been added in #53

[andrew-otiv]

Thanks for the update! We actually backed off of using async at all in our thread that manages the state machine. I should probably also appologize for not closing down our PR that was proposing this, but luckily it looks like you wanted to build this for some other purpose anyway. The no_std and embassy support you have in the works are neat too!