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Re-think, `msgspec`-multi-typed msg dialogs

The greasy details are strewn throughout a `msgspec` issue:
https://github.com/jcrist/msgspec/issues/140

and specifically this code was mostly written as part of POC example in
this comment:
https://github.com/jcrist/msgspec/issues/140#issuecomment-1177850792

This work obviously pertains to our desire and prep for typed messaging
and capabilities aware msg-oriented-protocols in #196, caps sec nods in

I added a "wants to have" method to `Context` showing how I think we
could offer a pretty neat msg-type-set-as-capability-for-protocol
system.
msgtypes
Tyler Goodlet 2022-07-07 15:48:16 -04:00
parent ec226463e3
commit 6b23435866
2 changed files with 102 additions and 4 deletions

View File

@ -699,6 +699,18 @@ class Context:
await self.chan.send({'started': value, 'cid': self.cid})
self._started_called = True
# TODO: msg capability context api1
# @acm
# async def enable_msg_caps(
# self,
# msg_subtypes: Union[
# list[list[Struct]],
# Protocol, # hypothetical type that wraps a msg set
# ],
# ) -> tuple[Callable, Callable]: # payload enc, dec pair
# ...
# TODO: do we need a restart api?
# async def restart(self) -> None:
# pass

View File

@ -45,10 +45,10 @@ Built-in messaging patterns, types, APIs and helpers.
from __future__ import annotations
from contextlib import contextmanager as cm
from pkgutil import resolve_name
from typing import Union, Any
from typing import Union, Any, Optional
from msgspec import Struct
from msgspec import Struct, Raw
from msgspec.msgpack import (
Encoder,
Decoder,
@ -125,8 +125,6 @@ def configure_native_msgs(
in all IPC transports and pop the codec on exit.
'''
global _lifo_codecs
# See "tagged unions" docs:
# https://jcristharif.com/msgspec/structs.html#tagged-unions
@ -149,3 +147,91 @@ def configure_native_msgs(
finally:
print("NONONONONON")
_lifo_codecs.pop()
class Header(Struct, tag=True):
'''
A msg header which defines payload properties
'''
uid: str
msgtype: Optional[str] = None
class Msg(Struct, tag=True):
'''
The "god" msg type, a box for task level msg types.
'''
header: Header
payload: Raw
_root_dec = Decoder(Msg)
_root_enc = Encoder()
# sub-decoders for retreiving embedded
# payload data and decoding to a sender
# side defined (struct) type.
_subdecs: dict[
Optional[str],
Decoder] = {
None: Decoder(Any),
}
@cm
def enable_context(
msg_subtypes: list[list[Struct]]
) -> Decoder:
for types in msg_subtypes:
first = types[0]
# register using the default tag_field of "type"
# which seems to map to the class "name".
tags = [first.__name__]
# create a tagged union decoder for this type set
type_union = Union[first]
for typ in types[1:]:
type_union |= typ
tags.append(typ.__name__)
dec = Decoder(type_union)
# register all tags for this union sub-decoder
for tag in tags:
_subdecs[tag] = dec
try:
yield dec
finally:
for tag in tags:
_subdecs.pop(tag)
def decmsg(msg: Msg) -> Any:
msg = _root_dec.decode(msg)
tag_field = msg.header.msgtype
dec = _subdecs[tag_field]
return dec.decode(msg.payload)
def encmsg(
dialog_id: str | int,
payload: Any,
) -> Msg:
tag_field = None
plbytes = _root_enc.encode(payload)
if b'type' in plbytes:
assert isinstance(payload, Struct)
tag_field = type(payload).__name__
payload = Raw(plbytes)
msg = Msg(
Header(dialog_id, tag_field),
payload,
)
return _root_enc.encode(msg)