[modbus] Avoid unnecessary IllegalArgumentException on dispose (openh…

…ab#8297)

[modbus] Do not raise exception on no-op operation of comms. interface

If communication interface is closed, you cannot naturally interact with
the device anymore. IllegalArgumentException is raised with all methods
that would need to interact with the device.

In this commit, close() and unregisterRegularPoll methods are not
raising the exception anymore since they are essentially no-ops with
closed communication interface. After all, close automatically
unregisters all registered regular polls. Thus, it should be considered
harmless to call these methods again on a closed instance, making them
mostly idempotent.

This change was motivated by seeing the IllegalStateException in the
wild, possibly triggered by certain dispose/initialize steps of things:
https://community.openhab.org/t/snip/102809/43

Signed-off-by: Sami Salonen <ssalonen@gmail.com>
Signed-off-by: Daan Meijer <daan@studioseptember.nl>

bundles/org.openhab.io.transport.modbus/src/main/java/org/openhab/io/transport/modbus/ModbusCommunicationInterface.java

@@ -74,10 +74,11 @@ public PollTask registerRegularPoll(ModbusReadRequestBlueprint request, long pol
  /**
  * Unregister regularly polled task
  *
+ * If this communication interface is closed already, the method returns immediately with false return value
+ *
  * @param task poll task to unregister
  * @return whether poll task was unregistered. Poll task is not unregistered in case of unexpected errors or
  * in the case where the poll task is not registered in the first place
- * @throws IllegalStateException when this communication has been closed already
  */
  public boolean unregisterRegularPoll(PollTask task);
 
@@ -93,4 +94,16 @@ public PollTask registerRegularPoll(ModbusReadRequestBlueprint request, long pol
  */
  public Future<?> submitOneTimeWrite(ModbusWriteRequestBlueprint request, ModbusWriteCallback resultCallback,
  ModbusFailureCallback<ModbusWriteRequestBlueprint> failureCallback);
+
+ /**
+ * Close this communication interface and try to free all resources associated with it
+ *
+ * Upon close, all polling tasks registered by this instance are unregistered. In addition, connections are closed
+ * eagerly if this was the last connection interface pointing to the endpoint.
+ *
+ * After close, the communication interface cannot be used to communicate with the device.
+ *
+ */
+ @Override
+ public void close() throws Exception;
 }

bundles/org.openhab.io.transport.modbus/src/main/java/org/openhab/io/transport/modbus/internal/ModbusManagerImpl.java

@@ -808,7 +808,8 @@ public PollTask registerRegularPoll(ModbusReadRequestBlueprint request, long pol
  public boolean unregisterRegularPoll(PollTask task) {
  synchronized (ModbusManagerImpl.this) {
  if (closed) {
- throw new IllegalStateException("Communication interface is closed already!");
+ // Closed already, nothing to unregister
+ return false;
  }
  pollTasksRegisteredByThisCommInterface.remove(task);
  ModbusSlaveConnectionFactoryImpl localConnectionFactory = connectionFactory;
@@ -853,7 +854,8 @@ public Future<?> submitOneTimeWrite(ModbusWriteRequestBlueprint request, ModbusW
  public void close() throws Exception {
  synchronized (ModbusManagerImpl.this) {
  if (closed) {
- throw new IllegalStateException("Communication interface is closed already!");
+ // Closed already, nothing to unregister
+ return;
  }
  // Iterate over all tasks registered by this communication interface, and unregister those
  // We copy pollTasksRegisteredByThisCommInterface temporarily so that unregisterRegularPoll can