Since `contextvars.ContextVar` seems to reset to the default in every
new task, switching to using `trio.lowlevel.RunVar` kinda gets close to
what we'd like where a child scope can override what's in the rent but
ideally without modifying the rent's. I tried `tricycle.TreeVar` as well
but it also seems to reset across (embedded) nurseries in our runtime;
need to try it again bc apparently that's not how it's suppose to work?
NOTE that for now i'm keeping the `.msg.types._ctxvar_MsgCodec` set to
the `msgspec` default (`Any` types) so that the test suite will still
pass until the runtime is ported to the new msg-spec + codec.
Surrounding and in support of all this the `Msg`-set impl deats changed
a bit as well as various stuff in `.msg` sub-mods:
- drop the `.pld` struct types for `Error`, `Start`, `StartAck` since we
don't really need the `.pld` payload field in those cases since
they're runtime control msgs for starting RPC tasks and handling
remote errors; we can just put the fields directly on each msg since
the user will never want/need to override the `.pld` field type.
- add a couple new runtime msgs and include them in `msg.__spec__`
and make them NOT inherit from `Msg` since they are runtime-specific
and thus have no need for `.pld` type constraints:
- `Aid` the actor-id identity handshake msg.
- `SpawnSpec`: the spawn data passed from a parent actor down to a
a child in `Actor._from_parent()` for which we need a shuttle
protocol msg, so might as well make it a pendatic one ;)
- fix some `Actor.uid` field types that were type-borked on `Error`
- add notes about how we need built-in `debug_mode` msgs in order to
avoid msg-type errors when using the TTY lock machinery and
a different `.pld` spec then the default `Any` is in use..
-> since `devx._debug.lock_tty_for_child()` and it's client side
`wait_for_parent_stdin_hijack()` use `Context.started('Locked')`
and `MsgStream.send('pdb_unlock')` string values as their `.pld`
contents we'd need to either always do a `ipc_pld_spec | str` or
pre-define some dedicated `Msg` types which get `Union`-ed in
for this?
- break out `msg.pretty_struct.Struct._sin_props()` into a helper func
`iter_fields()` since the impl doesn't require a struct instance.
- as mentioned above since `ContextVar` didn't work as anticipated
I next tried `tricycle.TreeVar` but that too didn't seem to keep
the `apply_codec()` setting intact across
`Portal.open_context()`/`Context.open_stream()` (it kept reverting to
the default `.pld: Any` default setting) so I finalized on
a trio.lowlevel.RunVar` for now despite it basically being
a `global`..
-> will probably come back to test this with `TreeVar` and some hot
tips i picked up from @mikenerone in the `trio` gitter, which i put in
comments surrounding proto-code.
4058d7c6c3