Expose WebSerial SLCAN readiness (#395)

This is useful for cyanide

---------

Co-authored-by: Pavel Kirienko <pavel.kirienko@gmail.com>

Author: maksimdrachov

src/pycyphal2/__init__.py

@@ -155,7 +155,7 @@ async def main():
 from ._transport import Transport as Transport
 from ._transport import TransportArrival as TransportArrival
 
-__version__ = "2.0.0.dev9"
+__version__ = "2.0.0.dev10"
 
 # pdoc needs __all__ to display re-exported members.
 __all__ = [

src/pycyphal2/can/webserial.py

@@ -99,6 +99,10 @@ def purge(self) -> None:
         if dropped > 0:
             _logger.debug("WebSerial SLCAN purge iface=%s dropped=%d", self._name, dropped)
 
+    async def wait_ready(self) -> None:
+        """Wait until the SLCAN adapter has been configured and opened."""
+        await self._ensure_initialized()
+
     async def receive(self) -> TimestampedFrame:
         self._raise_if_closed()
         if self._rx_task is None:

tests/can/test_webserial.py

@@ -86,6 +86,7 @@ async def _start(
     for i in range(len(encode_init_sequence(bitrate))):
         await _wait_for(_writes_reach(port, i + 2))  # writes: [close, cmd_0, ..., cmd_i]
         port.feed(_ACK)
+    await iface.wait_ready()
     return iface