Improved exception logging in Coba to now print exception __cause__ i…

…f it exists.

coba/context/loggers.py

@@ -297,6 +297,20 @@ def filter(self, log: Union[str,Exception]) -> str:
         elif isinstance(log, CobaException):
             return f"EXCEPTION: {log}"
         else:
-            tb  = ''.join(traceback.format_tb(log.__traceback__))
-            msg = ''.join(traceback.TracebackException.from_exception(log).format_exception_only())
-            return f"Unexpected exception:\n\n{tb}\n  {msg}"
+            return f'Unexpected exception:\n\n{self.format_exception(log)}'
+
+    def format_exception(self, ex: Exception):
+
+        out = []
+
+        if ex.__cause__ is not None:
+            out.append(self.format_exception(ex.__cause__))
+            out.append("The above exception was the direct cause of the following exception:\n")
+
+        tb  = ''.join(traceback.format_tb(ex.__traceback__))
+        msg = ''.join(traceback.TracebackException.from_exception(ex).format_exception_only())
+
+        if tb : out.append(tb)
+        if msg: out.append(f'  {msg}')
+
+        return '\n'.join(out)

coba/tests/test_context_loggers.py

@@ -603,10 +603,9 @@ def test_filter_exception(self):
 
         log = decorator.filter(exception)
 
-        tb  = ''.join(traceback.format_tb(exception.__traceback__))
         msg = ''.join(traceback.TracebackException.from_exception(exception).format_exception_only())
 
-        expected_log = f"Unexpected exception:\n\n{tb}\n  {msg}"
+        expected_log = f"Unexpected exception:\n\n  {msg}"
 
         self.assertEqual(log, expected_log)
 
@@ -627,6 +626,27 @@ def test_filter_exception_raise(self):
 
             self.assertEqual(log, expected_log)
 
+    def test_filter_exception_raise_with_caues(self):
+
+        decorator = ExceptLog()
+        outer_ex  = Exception("Out Exception")
+        inner_ex  = Exception("In Exception")
+
+        try:
+            raise inner_ex from outer_ex
+        except Exception as ex:
+            log = decorator.filter(ex)
+
+            tb = ''.join(traceback.format_tb(ex.__traceback__))
+            msg = ''.join(traceback.TracebackException.from_exception(ex).format_exception_only())
+
+            expected_log = (
+                'Unexpected exception:\n\n  Exception: Out Exception\n\nThe above exception '
+                f'was the direct cause of the following exception:\n\n{tb}\n  {msg}'
+            )
+
+            self.assertEqual(log, expected_log)
+
     def test_filter_coba_exception(self):
 
         decorator = ExceptLog()