Add trio message assembler.

Also uniformize code & tests with other implementations.

Author: aaugustin

src/websockets/asyncio/messages.py

@@ -81,8 +81,7 @@ class Assembler:
 
     """
 
-    # coverage reports incorrectly: "line NN didn't jump to the function exit"
-    def __init__(  # pragma: no cover
+    def __init__(
         self,
         high: int | None = None,
         low: int | None = None,
@@ -155,15 +154,15 @@ async def get(self, decode: bool | None = None) -> Data:
         # until get() fetches a complete message or is canceled.
 
         try:
-            # First frame
+            # Fetch the first frame.
             frame = await self.frames.get(not self.closed)
             self.maybe_resume()
             assert frame.opcode is OP_TEXT or frame.opcode is OP_BINARY
             if decode is None:
                 decode = frame.opcode is OP_TEXT
             frames = [frame]
 
-            # Following frames, for fragmented messages
+            # Fetch subsequent frames for fragmented messages.
             while not frame.fin:
                 try:
                     frame = await self.frames.get(not self.closed)
@@ -230,7 +229,7 @@ async def get_iter(self, decode: bool | None = None) -> AsyncIterator[Data]:
         # If get_iter() raises an exception e.g. in decoder.decode(),
         # get_in_progress remains set and the connection becomes unusable.
 
-        # First frame
+        # Yield the first frame.
         try:
             frame = await self.frames.get(not self.closed)
         except asyncio.CancelledError:
@@ -247,7 +246,7 @@ async def get_iter(self, decode: bool | None = None) -> AsyncIterator[Data]:
             # Convert to bytes when frame.data is a bytearray.
             yield bytes(frame.data)
 
-        # Following frames, for fragmented messages
+        # Yield subsequent frames for fragmented messages.
         while not frame.fin:
             # We cannot handle asyncio.CancelledError because we don't buffer
             # previous fragments — we're streaming them. Canceling get_iter()
@@ -280,22 +279,22 @@ def put(self, frame: Frame) -> None:
 
     def maybe_pause(self) -> None:
         """Pause the writer if queue is above the high water mark."""
-        # Skip if flow control is disabled
+        # Skip if flow control is disabled.
         if self.high is None:
             return
 
-        # Check for "> high" to support high = 0
+        # Check for "> high" to support high = 0.
         if len(self.frames) > self.high and not self.paused:
             self.paused = True
             self.pause()
 
     def maybe_resume(self) -> None:
         """Resume the writer if queue is below the low water mark."""
-        # Skip if flow control is disabled
+        # Skip if flow control is disabled.
         if self.low is None:
             return
 
-        # Check for "<= low" to support low = 0
+        # Check for "<= low" to support low = 0.
         if len(self.frames) <= self.low and self.paused:
             self.paused = False
             self.resume()

src/websockets/sync/messages.py

@@ -165,7 +165,7 @@ def get(self, timeout: float | None = None, decode: bool | None = None) -> Data:
         try:
             deadline = Deadline(timeout)
 
-            # First frame
+            # Fetch the first frame.
             frame = self.get_next_frame(deadline.timeout(raise_if_elapsed=False))
             with self.mutex:
                 self.maybe_resume()
@@ -174,7 +174,7 @@ def get(self, timeout: float | None = None, decode: bool | None = None) -> Data:
                 decode = frame.opcode is OP_TEXT
             frames = [frame]
 
-            # Following frames, for fragmented messages
+            # Fetch subsequent frames for fragmented messages.
             while not frame.fin:
                 try:
                     frame = self.get_next_frame(
@@ -245,7 +245,7 @@ def get_iter(self, decode: bool | None = None) -> Iterator[Data]:
         # If get_iter() raises an exception e.g. in decoder.decode(),
         # get_in_progress remains set and the connection becomes unusable.
 
-        # First frame
+        # Yield the first frame.
         frame = self.get_next_frame()
         with self.mutex:
             self.maybe_resume()
@@ -259,7 +259,7 @@ def get_iter(self, decode: bool | None = None) -> Iterator[Data]:
             # Convert to bytes when frame.data is a bytearray.
             yield bytes(frame.data)
 
-        # Following frames, for fragmented messages
+        # Yield subsequent frames for fragmented messages.
         while not frame.fin:
             frame = self.get_next_frame()
             with self.mutex:
@@ -300,26 +300,26 @@ def put(self, frame: Frame) -> None:
 
     def maybe_pause(self) -> None:
         """Pause the writer if queue is above the high water mark."""
-        # Skip if flow control is disabled
+        # Skip if flow control is disabled.
         if self.high is None:
             return
 
         assert self.mutex.locked()
 
-        # Check for "> high" to support high = 0
+        # Check for "> high" to support high = 0.
         if self.frames.qsize() > self.high and not self.paused:
             self.paused = True
             self.pause()
 
     def maybe_resume(self) -> None:
         """Resume the writer if queue is below the low water mark."""
-        # Skip if flow control is disabled
+        # Skip if flow control is disabled.
         if self.low is None:
             return
 
         assert self.mutex.locked()
 
-        # Check for "<= low" to support low = 0
+        # Check for "<= low" to support low = 0.
         if self.frames.qsize() <= self.low and self.paused:
             self.paused = False
             self.resume()