pybricksdev.connections.pybricks: make line handler optional

Long running programs may want to ignore stdout from the hub instead of
maintaining an infinite log. We also plan on adding an optional stdout
subscription that is an alternative to the line handler. So in these
cases, it is desireable to disable the default line handler.

Author: dlech

pybricksdev/connections/pybricks.py

@@ -87,6 +87,9 @@ def __init__(self):
         self._capability_flags = HubCapabilityFlag(0)
         self._max_user_program_size = 0
 
+        # whether to enable line handler features or not
+        self._enable_line_handler = False
+
         # buffered stdout from the hub for splitting into lines
         self._stdout_buf = bytearray()
 
@@ -198,15 +201,19 @@ def _nus_handler(self, sender, data: bytearray) -> None:
         # support legacy firmware where the Nordic UART service
         # was used for stdio
         if self._legacy_stdio:
-            self._handle_line_data(data)
+            if self._enable_line_handler:
+                self._handle_line_data(data)
 
     def _pybricks_service_handler(self, _: int, data: bytes) -> None:
         if data[0] == Event.STATUS_REPORT:
             # decode the payload
             (flags,) = struct.unpack_from("<I", data, 1)
             self.status_observable.on_next(StatusFlag(flags))
         elif data[0] == Event.WRITE_STDOUT:
-            self._handle_line_data(data[1:])
+            payload = data[1:]
+
+            if self._enable_line_handler:
+                self._handle_line_data(payload)
 
     async def connect(self, device: BLEDevice):
         """Connects to a device that was discovered with :meth:`pybricksdev.ble.find_device`
@@ -422,7 +429,11 @@ async def stop_user_program(self) -> None:
         )
 
     async def run(
-        self, py_path: str, wait: bool = True, print_output: bool = True
+        self,
+        py_path: str,
+        wait: bool = True,
+        print_output: bool = True,
+        line_handler: bool = True,
     ) -> None:
         """
         Compiles and runs a user program.
@@ -431,6 +442,7 @@ async def run(
             py_path: The path to the .py file to compile.
             wait: If true, wait for the user program to stop before returning.
             print_output: If true, echo stdout of the hub to ``sys.stdout``.
+            line_handler: If true enable hub stdout line handler features.
         """
         if self.connection_state_observable.value != ConnectionState.CONNECTED:
             raise RuntimeError("not connected")
@@ -442,6 +454,7 @@ async def run(
         self._stdout_line_queue = asyncio.Queue()
         self.print_output = print_output
         self.script_dir, _ = os.path.split(py_path)
+        self._enable_line_handler = line_handler
 
         # maintain compatibility with older firmware (Pybricks profile < 1.2.0).
         if self._mpy_abi_version: