Add close() method to Channel and ByteChannel

Python can now close channels explicitly:
  channel.close()
  byte_channel.close()

Also adds context manager support:
  with Channel(ref) as ch:
      for msg in ch:
          process(msg)
  # channel automatically closed

Author: benoitc

c_src/py_callback.c

@@ -2856,6 +2856,38 @@ static PyObject *erlang_channel_is_closed_impl(PyObject *self, PyObject *args) {
     }
 }
 
+/**
+ * @brief Close a channel from Python
+ *
+ * Usage: erlang._channel_close(channel_ref)
+ * Returns: True on success
+ * Raises: TypeError if invalid reference
+ */
+static PyObject *erlang_channel_close_impl(PyObject *self, PyObject *args) {
+    (void)self;
+    PyObject *capsule;
+
+    if (!PyArg_ParseTuple(args, "O", &capsule)) {
+        return NULL;
+    }
+
+    if (!PyCapsule_CheckExact(capsule)) {
+        PyErr_SetString(PyExc_TypeError, "expected channel reference");
+        return NULL;
+    }
+
+    py_channel_t *channel = (py_channel_t *)PyCapsule_GetPointer(capsule, CHANNEL_CAPSULE_NAME);
+    if (channel == NULL) {
+        PyErr_SetString(PyExc_ValueError, "invalid channel reference");
+        return NULL;
+    }
+
+    /* Close the channel - this wakes any waiting receivers */
+    channel_close(channel);
+
+    Py_RETURN_TRUE;
+}
+
 /* ============================================================================
  * ByteChannel Methods (raw bytes, no term conversion)
  * ============================================================================ */
@@ -3328,6 +3360,10 @@ static PyMethodDef ErlangModuleMethods[] = {
      "Check if channel is closed.\n"
      "Usage: erlang._channel_is_closed(channel_ref)\n"
      "Returns: True if closed, False otherwise."},
+    {"_channel_close", erlang_channel_close_impl, METH_VARARGS,
+     "Close a channel.\n"
+     "Usage: erlang._channel_close(channel_ref)\n"
+     "Returns: True. Wakes any waiting receivers."},
     /* ByteChannel methods (raw bytes, no term conversion) */
     {"_byte_channel_try_receive_bytes", erlang_byte_channel_try_receive_bytes_impl, METH_VARARGS,
      "ByteChannel receive (non-blocking, raw bytes).\n"

priv/_erlang_impl/_byte_channel.py

@@ -307,5 +307,29 @@ def _is_closed(self) -> bool:
         except Exception:
             return True
 
+    def close(self):
+        """Close the byte channel.
+
+        Closes the channel and wakes any waiting receivers with ByteChannelClosed.
+        Safe to call multiple times - subsequent calls have no effect.
+
+        Example:
+            byte_channel.close()  # Signal no more data
+        """
+        import erlang
+        try:
+            erlang._channel_close(self._ref)
+        except Exception:
+            pass  # Ignore errors on close (may already be closed)
+
+    def __enter__(self):
+        """Context manager entry - returns self."""
+        return self
+
+    def __exit__(self, exc_type, exc_val, exc_tb):
+        """Context manager exit - closes the channel."""
+        self.close()
+        return False
+
     def __repr__(self):
         return f"<ByteChannel ref={self._ref!r}>"

priv/_erlang_impl/_channel.py

@@ -286,6 +286,30 @@ def _is_closed(self):
         except Exception:
             return True
 
+    def close(self):
+        """Close the channel.
+
+        Closes the channel and wakes any waiting receivers with ChannelClosed.
+        Safe to call multiple times - subsequent calls have no effect.
+
+        Example:
+            channel.close()  # Signal no more data
+        """
+        import erlang
+        try:
+            erlang._channel_close(self._ref)
+        except Exception:
+            pass  # Ignore errors on close (may already be closed)
+
+    def __enter__(self):
+        """Context manager entry - returns self."""
+        return self
+
+    def __exit__(self, exc_type, exc_val, exc_tb):
+        """Context manager exit - closes the channel."""
+        self.close()
+        return False
+
     def __repr__(self):
         return f"<Channel ref={self._ref!r}>"