Feature request: Allow explicit serialization of custom exception attributes in LambdaJsonEncoder #2728

--- a/packages/logger/src/formatter/LogFormatter.ts
+++ b/packages/logger/src/formatter/LogFormatter.ts
@@ -104,16 +104,24 @@ abstract class LogFormatter {
    * @param error - Error to format
    */
   public formatError(error: Error): LogAttributes {
-    return {
-      name: error.name,
+    const { name, message, stack, cause, ...errorAttributes } = error;
+    const formattedError: LogAttributes = {
+      name,
       location: this.getCodeLocation(error.stack),
-      message: error.message,
-      stack: error.stack,
+      message,
+      stack,
       cause:
         error.cause instanceof Error
           ? this.formatError(error.cause)
           : error.cause,
     };
+    for (const key in error) {
+      if (typeof key === 'string' && !['name', 'message', 'stack', 'cause'].includes(key)) {
+          formattedError[key] = (errorAttributes as Record<string, unknown>)[key];
+      }
+    }
+
+    return formattedError;
   }

diff --git a/powertools-logging/powertools-logging-logback/src/main/java/software/amazon/lambda/powertools/logging/logback/ExceptionAttributesProvider.java b/powertools-logging/powertools-logging-logback/src/main/java/software/amazon/lambda/powertools/logging/logback/ExceptionAttributesProvider.java
new file mode 100644
--- /dev/null
+++ b/powertools-logging/powertools-logging-logback/src/main/java/software/amazon/lambda/powertools/logging/logback/ExceptionAttributesProvider.java
@@ -0,0 +1,38 @@
+/*
+ * Copyright 2023 Amazon.com, Inc. or its affiliates.
+ * Licensed under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package software.amazon.lambda.powertools.logging.logback;
+
+import java.util.Map;
+
+/**
+ * Provides additional attributes to add to the "error" object logged by the {@link LambdaJsonEncoder}.
+ * The standard attributes (name, message, stack) cannot be overridden.
+ * <br/>
+ * <pre>{@code
+ *     <encoder class="software.amazon.lambda.powertools.logging.logback.LambdaJsonEncoder">
+ *         <exceptionAttributesProvider class="com.example.PaymentExceptionAttributes"/>
+ *     </encoder>
+ * }</pre>
+ */
+public interface ExceptionAttributesProvider {
+
+    /**
+     * Returns the attributes to add to the "error" object for the given exception.
+     *
+     * @param throwable the logged exception
+     * @return extra attributes to add to the "error" object, or an empty map for none
+     */
+    Map<String, Object> attributes(Throwable throwable);
+}
diff --git a/powertools-logging/powertools-logging-logback/src/main/java/software/amazon/lambda/powertools/logging/logback/LambdaJsonEncoder.java b/powertools-logging/powertools-logging-logback/src/main/java/software/amazon/lambda/powertools/logging/logback/LambdaJsonEncoder.java
--- a/powertools-logging/powertools-logging-logback/src/main/java/software/amazon/lambda/powertools/logging/logback/LambdaJsonEncoder.java
+++ b/powertools-logging/powertools-logging-logback/src/main/java/software/amazon/lambda/powertools/logging/logback/LambdaJsonEncoder.java
@@ -51,6 +51,7 @@ public class LambdaJsonEncoder extends EncoderBase<ILoggingEvent> {
     protected String timestampFormatTimezoneId = null;
     private boolean includeThreadInfo = false;
     private boolean includePowertoolsInfo = true;
+    private ExceptionAttributesProvider exceptionAttributesProvider = null;
 
     @Override
     public byte[] headerBytes() {
@@ -137,15 +138,15 @@ public class LambdaJsonEncoder extends EncoderBase<ILoggingEvent> {
         IThrowableProxy throwableProxy = event.getThrowableProxy();
         if (throwableProxy != null) {
             if (throwableConverter != null) {
-                serializeException(serializer, throwableProxy.getClassName(),
+                serializeException(serializer, throwableProxy, throwableProxy.getClassName(),
                         throwableProxy.getMessage(), throwableConverter.convert(event));
             } else if (throwableProxy instanceof ThrowableProxy) {
                 Throwable throwable = ((ThrowableProxy) throwableProxy).getThrowable();
-                serializeException(serializer, throwable.getClass().getName(), throwable.getMessage(),
-                        Arrays.toString(throwable.getStackTrace()));
+                serializeException(serializer, throwableProxy, throwable.getClass().getName(),
+                        throwable.getMessage(), Arrays.toString(throwable.getStackTrace()));
             } else {
-                serializeException(serializer, throwableProxy.getClassName(), throwableProxy.getMessage(), throwableProxyConverter.convert(
-                        event));
+                serializeException(serializer, throwableProxy, throwableProxy.getClassName(),
+                        throwableProxy.getMessage(), throwableProxyConverter.convert(event));
             }
         }
     }
@@ -255,8 +256,33 @@ public class LambdaJsonEncoder extends EncoderBase<ILoggingEvent> {
         this.includePowertoolsInfo = includePowertoolsInfo;
     }
 
-    private void serializeException(JsonSerializer serializer, String className, String message, String stackTrace) {
+    /**
+     * Specify a provider of additional attributes to add to the "error" object
+     * (default is <b>null</b>, no additional attributes):
+     * <br/>
+     * <pre>{@code
+     *     <encoder class="software.amazon.lambda.powertools.logging.logback.LambdaJsonEncoder">
+     *         <exceptionAttributesProvider class="com.example.PaymentExceptionAttributes"/>
+     *     </encoder>
+     * }</pre>
+     *
+     * @param exceptionAttributesProvider provider of the additional exception attributes
+     */
+    public void setExceptionAttributesProvider(ExceptionAttributesProvider exceptionAttributesProvider) {
+        this.exceptionAttributesProvider = exceptionAttributesProvider;
+    }
+
+    private void serializeException(JsonSerializer serializer, IThrowableProxy throwableProxy, String className,
+            String message, String stackTrace) {
         Map<Object, Object> map = new HashMap<>();
+        if (exceptionAttributesProvider != null && throwableProxy instanceof ThrowableProxy) {
+            Map<String, Object> attributes =
+                    exceptionAttributesProvider.attributes(((ThrowableProxy) throwableProxy).getThrowable());
+            if (attributes != null) {
+                map.putAll(attributes);
+            }
+        }
+        // standard attributes are put last so that they cannot be overridden
         map.put(EXCEPTION_MSG_ATTR_NAME, message);
         map.put(EXCEPTION_CLASS_ATTR_NAME, className);
         map.put(EXCEPTION_STACK_ATTR_NAME, stackTrace);