update comment

Author: nytian

azurefunctions/src/main/java/com/microsoft/durabletask/azurefunctions/internal/middleware/ActivityMiddleware.java

@@ -78,15 +78,16 @@ public void invoke(MiddlewareContext context, MiddlewareChain chain) throws Exce
                 throw e;
             }
 
+            String serializedFailureDetails;
             try {
-                throw new StructuredActivityFailure(
-                        FAILURE_DETAILS_JSON_PRINTER.print(failureDetails.toProto()));
-            } catch (InvalidProtocolBufferException serializationException) {
+                serializedFailureDetails = FAILURE_DETAILS_JSON_PRINTER.print(failureDetails.toProto());
+            } catch (InvalidProtocolBufferException | RuntimeException conversionException) {
                 LOGGER.log(Level.WARNING,
-                        "Failed to serialize structured failure details; rethrowing the original exception.",
-                        serializationException);
+                        "Failed to convert or serialize structured failure details; rethrowing the original exception.",
+                        conversionException);
                 throw e;
             }
+            throw new StructuredActivityFailure(serializedFailureDetails);
         }
     }
 

azurefunctions/src/test/java/com/microsoft/durabletask/azurefunctions/internal/middleware/ActivityMiddlewareTest.java

@@ -206,6 +206,24 @@ void rethrowsOriginalWhenProviderThrows() {
         assertSame(original, thrown);
     }
 
+    @Test
+    @DisplayName("Rethrows the original exception unchanged when failure detail conversion fails")
+    void rethrowsOriginalWhenFailureDetailConversionFails() {
+        setProviderSupplier(() -> exception -> {
+            Map<String, Object> properties = new LinkedHashMap<>();
+            properties.put(null, "value");
+            return properties;
+        });
+
+        BusinessException original = new BusinessException("boom");
+        ActivityMiddleware middleware = new ActivityMiddleware();
+
+        Exception thrown = assertThrows(Exception.class,
+                () -> middleware.invoke(activityContext(), throwingChain(original)));
+
+        assertSame(original, thrown);
+    }
+
     @Test
     @DisplayName("Does not invoke the provider for non-activity triggers")
     void passesThroughNonActivityTrigger() throws Exception {