emcy: catch callback exceptions and expand test coverage

- Fix bug where an exception in one EMCY callback would abort all
  subsequent callbacks; now logs the exception and continues
- Add test for callback exception handling (verifies fix)
- Add tests for EmcyConsumer initialization, multiple callback order,
  error reset variants, wait timeout edge cases, concurrent errors
- Add tests for EmcyError initialization types and str representation
- Add tests for EmcyProducer initialization, send/reset edge cases
- Add TestEmcyIntegration class using network.subscribe() for
  producer-consumer roundtrip tests
- Remove superfluous inline comments per reviewer feedback (acolomb)
- Convert leading comment to docstring in test_emcy_consumer_on_emcy

Addresses review feedback from PR #604 by yuvraj-kolkar17.

Author: friederschueler

canopen/emcy.py

@@ -39,7 +39,10 @@ def on_emcy(self, can_id, data, timestamp):
             self.emcy_received.notify_all()
 
         for callback in self.callbacks:
-            callback(entry)
+            try:
+                callback(entry)
+            except Exception:
+                logger.exception("Exception in EMCY callback")
 
     def add_callback(self, callback: Callable[[EmcyError], None]):
         """Get notified on EMCY messages from this node.

test/test_emcy.py

@@ -25,13 +25,12 @@ def check_error(self, err, code, reg, data, ts):
         self.assertAlmostEqual(err.timestamp, ts)
 
     def test_emcy_consumer_on_emcy(self):
-        # Make sure multiple callbacks receive the same information.
+        """Make sure multiple callbacks receive the same information."""
         acc1 = []
         acc2 = []
         self.emcy.add_callback(lambda err: acc1.append(err))
         self.emcy.add_callback(lambda err: acc2.append(err))
 
-        # Dispatch an EMCY datagram.
         self.emcy.on_emcy(0x81, b'\x01\x20\x02\x00\x01\x02\x03\x04', 1000)
 
         self.assertEqual(len(self.emcy.log), 1)
@@ -45,7 +44,6 @@ def test_emcy_consumer_on_emcy(self):
                 data=bytes([0, 1, 2, 3, 4]), ts=1000,
             )
 
-        # Dispatch a new EMCY datagram.
         self.emcy.on_emcy(0x81, b'\x10\x90\x01\x04\x03\x02\x01\x00', 2000)
         self.assertEqual(len(self.emcy.log), 2)
         self.assertEqual(len(self.emcy.active), 2)
@@ -58,7 +56,6 @@ def test_emcy_consumer_on_emcy(self):
                 data=bytes([4, 3, 2, 1, 0]), ts=2000,
             )
 
-        # Dispatch an EMCY reset.
         self.emcy.on_emcy(0x81, b'\x00\x00\x00\x00\x00\x00\x00\x00', 2000)
         self.assertEqual(len(self.emcy.log), 3)
         self.assertEqual(len(self.emcy.active), 0)
@@ -123,6 +120,65 @@ def push_reset():
             t.start()
             self.assertIsNone(self.emcy.wait(0x9000, TIMEOUT))
 
+    def test_emcy_consumer_initialization(self):
+        consumer = canopen.emcy.EmcyConsumer()
+        self.assertEqual(consumer.log, [])
+        self.assertEqual(consumer.active, [])
+        self.assertEqual(consumer.callbacks, [])
+
+    def test_emcy_consumer_multiple_callbacks(self):
+        """Test adding multiple callbacks and their execution order."""
+        call_order = []
+        self.emcy.add_callback(lambda err: call_order.append('callback1'))
+        self.emcy.add_callback(lambda err: call_order.append('callback2'))
+        self.emcy.add_callback(lambda err: call_order.append('callback3'))
+        self.emcy.on_emcy(0x81, b'\x01\x20\x02\x00\x01\x02\x03\x04', 1000)
+        self.assertEqual(call_order, ['callback1', 'callback2', 'callback3'])
+
+    def test_emcy_consumer_callback_exception_handling(self):
+        """Test that callback exceptions don't break other callbacks or the system."""
+        successful_callbacks = []
+        self.emcy.add_callback(lambda err: successful_callbacks.append('success1'))
+        self.emcy.add_callback(
+            lambda err: exec('raise ValueError("Test exception in callback")')
+        )
+        self.emcy.add_callback(lambda err: successful_callbacks.append('success2'))
+        self.emcy.on_emcy(0x81, b'\x01\x20\x02\x00\x01\x02\x03\x04', 1000)
+        self.assertEqual(successful_callbacks, ['success1', 'success2'])
+
+    def test_emcy_consumer_error_reset_variants(self):
+        """Test different error reset code patterns."""
+        self.emcy.on_emcy(0x81, b'\x01\x20\x02\x00\x01\x02\x03\x04', 1000)
+        self.emcy.on_emcy(0x81, b'\x10\x90\x01\x04\x03\x02\x01\x00', 2000)
+        self.assertEqual(len(self.emcy.active), 2)
+        self.emcy.on_emcy(0x81, b'\x00\x00\x00\x00\x00\x00\x00\x00', 3000)
+        self.assertEqual(len(self.emcy.active), 0)
+        self.emcy.on_emcy(0x81, b'\x01\x30\x02\x00\x01\x02\x03\x04', 4000)
+        self.assertEqual(len(self.emcy.active), 1)
+        self.emcy.on_emcy(0x81, b'\x99\x00\x01\x00\x00\x00\x00\x00', 5000)
+        self.assertEqual(len(self.emcy.active), 0)
+
+    def test_emcy_consumer_wait_timeout_edge_cases(self):
+        """Test wait method with various timeout scenarios."""
+        result = self.emcy.wait(timeout=0)
+        self.assertIsNone(result)
+        result = self.emcy.wait(timeout=0.001)
+        self.assertIsNone(result)
+
+    def test_emcy_consumer_wait_concurrent_errors(self):
+        """Test wait method when multiple errors arrive concurrently."""
+        def push_multiple_errors():
+            self.emcy.on_emcy(0x81, b'\x01\x20\x01\x01\x02\x03\x04\x05', 100)
+            self.emcy.on_emcy(0x81, b'\x02\x20\x01\x01\x02\x03\x04\x05', 101)
+            self.emcy.on_emcy(0x81, b'\x03\x20\x01\x01\x02\x03\x04\x05', 102)
+        t = threading.Timer(TIMEOUT / 2, push_multiple_errors)
+        with self.assertLogs(level=logging.INFO):
+            t.start()
+            err = self.emcy.wait(0x2003, timeout=TIMEOUT)
+        t.join(TIMEOUT)
+        self.assertIsNotNone(err)
+        self.assertEqual(err.code, 0x2003)
+
 
 class TestEmcyError(unittest.TestCase):
     def test_emcy_error(self):
@@ -180,6 +236,26 @@ def check(code, expected):
         check(0xff00, "Device Specific")
         check(0xffff, "Device Specific")
 
+    def test_emcy_error_initialization_types(self):
+        """Test EmcyError initialization with various data types."""
+        error = EmcyError(0x1000, 0, b'', 123.456)
+        self.assertEqual(error.code, 0x1000)
+        self.assertEqual(error.register, 0)
+        self.assertEqual(error.data, b'')
+        self.assertEqual(error.timestamp, 123.456)
+        error = EmcyError(0xFFFF, 0xFF, b'\xFF' * 5, float('inf'))
+        self.assertEqual(error.code, 0xFFFF)
+        self.assertEqual(error.register, 0xFF)
+        self.assertEqual(error.data, b'\xFF' * 5)
+        self.assertEqual(error.timestamp, float('inf'))
+
+    def test_emcy_error_str_edge_cases(self):
+        for code in (0x0000, 0x0001, 0x0100, 0xFFFF):
+            error = EmcyError(code, 0, b'', 1000)
+            s = str(error)
+            self.assertIsInstance(s, str)
+            self.assertIn(f"0x{code:04X}", s)
+
 
 class TestEmcyProducer(unittest.TestCase):
     def setUp(self):
@@ -220,6 +296,91 @@ def check(*args, res):
         check(3, res=b'\x00\x00\x03\x00\x00\x00\x00\x00')
         check(3, b"\xaa\xbb", res=b'\x00\x00\x03\xaa\xbb\x00\x00\x00')
 
+    def test_emcy_producer_initialization(self):
+        producer = canopen.emcy.EmcyProducer(0x123)
+        self.assertEqual(producer.cob_id, 0x123)
+        self.assertIsNotNone(producer.network)
+
+    def test_emcy_producer_send_edge_cases(self):
+        self.emcy.send(0xFFFF, 0xFF, b'\xFF\xFF\xFF\xFF\xFF')
+        self.check_response(b'\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF')
+        self.emcy.send(0x0000, 0x00)
+        self.check_response(b'\x00\x00\x00\x00\x00\x00\x00\x00')
+        self.emcy.send(0x1234, 0x56, b'\xAB\xCD')
+        self.check_response(b'\x34\x12\x56\xAB\xCD\x00\x00\x00')
+        self.emcy.send(0x1234, 0x56, b'\xAB\xCD\xEF\x12\x34')
+        self.check_response(b'\x34\x12\x56\xAB\xCD\xEF\x12\x34')
+
+    def test_emcy_producer_reset_edge_cases(self):
+        self.emcy.reset(0xFF)
+        self.check_response(b'\x00\x00\xFF\x00\x00\x00\x00\x00')
+        self.emcy.reset(0xFF, b'\xFF\xFF\xFF\xFF\xFF')
+        self.check_response(b'\x00\x00\xFF\xFF\xFF\xFF\xFF\xFF')
+        self.emcy.reset(0x12, b'\xAB\xCD')
+        self.check_response(b'\x00\x00\x12\xAB\xCD\x00\x00\x00')
+
+
+class TestEmcyIntegration(unittest.TestCase):
+    """Integration tests for EMCY producer and consumer."""
+
+    def setUp(self):
+        self.txbus = can.Bus(interface="virtual")
+        self.rxbus = can.Bus(interface="virtual")
+        self.net = canopen.Network(self.txbus)
+        self.net.NOTIFIER_SHUTDOWN_TIMEOUT = 0.0
+        self.net.connect()
+        self.rx_net = canopen.Network(self.rxbus)
+        self.rx_net.NOTIFIER_SHUTDOWN_TIMEOUT = 0.0
+        self.rx_net.connect()
+        self.producer = canopen.emcy.EmcyProducer(0x081)
+        self.producer.network = self.net
+        self.consumer = canopen.emcy.EmcyConsumer()
+        self.rx_net.subscribe(0x081, self.consumer.on_emcy)
+
+    def tearDown(self):
+        self.net.disconnect()
+        self.rx_net.disconnect()
+        self.txbus.shutdown()
+        self.rxbus.shutdown()
+
+    def test_producer_consumer_integration(self):
+        """Test that producer and consumer work together."""
+        received_errors = []
+        self.consumer.add_callback(lambda err: received_errors.append(err))
+        t = threading.Timer(
+            TIMEOUT / 2,
+            lambda: self.producer.send(0x2001, 0x02, b'\x01\x02\x03\x04\x05'),
+        )
+        with self.assertLogs(level=logging.INFO):
+            t.start()
+            err = self.consumer.wait(0x2001, timeout=TIMEOUT)
+        t.join(TIMEOUT)
+        self.assertIsNotNone(err)
+        self.assertEqual(err.code, 0x2001)
+        self.assertEqual(err.register, 0x02)
+        self.assertEqual(err.data, b'\x01\x02\x03\x04\x05')
+        self.assertEqual(received_errors, [err])
+
+    def test_producer_reset_consumer_integration(self):
+        """Test producer reset clears consumer active errors."""
+        t = threading.Timer(
+            TIMEOUT / 2,
+            lambda: self.producer.send(0x2001, 0x02, b'\x01\x02\x03\x04\x05'),
+        )
+        with self.assertLogs(level=logging.INFO):
+            t.start()
+            self.consumer.wait(0x2001, timeout=TIMEOUT)
+        t.join(TIMEOUT)
+        self.assertEqual(len(self.consumer.active), 1)
+        t = threading.Timer(TIMEOUT / 2, self.producer.reset)
+        with self.assertLogs(level=logging.INFO):
+            t.start()
+            err = self.consumer.wait(timeout=TIMEOUT)
+        t.join(TIMEOUT)
+        self.assertIsNotNone(err)
+        self.assertEqual(len(self.consumer.active), 0)
+        self.assertEqual(len(self.consumer.log), 2)
+
 
 if __name__ == "__main__":
     unittest.main()