Close crt bridge stream on end_stream if empty

This is a followup to #432. I think the issue was that end_stream
was getting called when the buffer was already empty, which would
put it in an incomplete state. Unfortunately that fix also left it
in an incomplete (but now working) state. This make sure it doesn't
get into that incomplete state and adds a failing test for that
case.

Author: JordonPhillips

packages/smithy-http/src/smithy_http/aio/crt.py

@@ -369,8 +369,10 @@ def read(self, size: int | None = -1) -> bytes:
 
         if len(self._chunks) == 0:
             if self._done:
+                self.close()
                 return b""
             else:
+                # When the CRT recieves this, it'll try again
                 raise BlockingIOError("read")
 
         # We could compile all the chunks here instead of just returning
@@ -429,4 +431,7 @@ def close(self) -> None:
 
     def end_stream(self) -> None:
         """End the stream, letting any remaining chunks be read before it is closed."""
-        self._done = True
+        if len(self._chunks) == 0:
+            self.close()
+        else:
+            self._done = True

packages/smithy-http/tests/unit/aio/test_crt.py

@@ -95,6 +95,12 @@ def test_done_stream_read() -> None:
     assert stream.read() == b""
 
 
+def test_end_empty_stream() -> None:
+    stream = BufferableByteStream()
+    stream.end_stream()
+    assert stream.read() == b""
+
+
 def test_stream_read1() -> None:
     stream = BufferableByteStream()
     stream.write(b"foo")