Use weakrefs for Tape streams (#117)

Signed-off-by: Michel Hidalgo <[email protected]>

bdai_ros2_wrappers/bdai_ros2_wrappers/utilities.py

@@ -7,7 +7,8 @@
 import queue
 import threading
 import warnings
-from collections.abc import Mapping
+import weakref
+from collections.abc import Mapping, MutableSet
 from typing import Any, Callable, Generic, Iterator, List, Optional, Tuple, TypeVar, Union
 
 import rclpy.clock
@@ -142,7 +143,7 @@ def __init__(self, max_length: Optional[int] = None) -> None:
             max_length: optional maximum tape length.
         """
         self._lock = threading.Lock()
-        self._streams: List[Tape.Stream[T]] = []
+        self._streams: MutableSet[Tape.Stream[T]] = weakref.WeakSet()
         self._content: Optional[collections.deque] = None
         if max_length is None or max_length > 0:
             self._content = collections.deque(maxlen=max_length)
@@ -249,7 +250,7 @@ def content(
             stream: Optional[Tape.Stream] = None
             if follow and not self._closed:
                 stream = Tape.Stream(buffer_size, label)
-                self._streams.append(stream)
+                self._streams.add(stream)
 
         def _generator() -> Iterator:
             nonlocal content, stream

bdai_ros2_wrappers/test/test_utilities.py

@@ -4,7 +4,21 @@
 
 import pytest
 
-from bdai_ros2_wrappers.utilities import either_or, ensure, namespace_with
+from bdai_ros2_wrappers.utilities import Tape, either_or, ensure, namespace_with
+
+
+def test_tape_drops_unused_streams() -> None:
+    tape: Tape[int] = Tape(max_length=0)
+
+    stream = tape.content(follow=True)
+    expected_value = 42
+    tape.write(expected_value)
+    value = next(stream)
+    assert value == expected_value
+
+    del stream
+
+    assert len(tape._streams) == 0
 
 
 def test_either_or() -> None: