KAFKA-15353: make sure AlterPartitionRequest.build() is idempotent (#14236)

As described in https://issues.apache.org/jira/browse/KAFKA-15353
When the AlterPartitionRequest version is < 3 and its builder.build is called multiple times, both newIsrWithEpochs and newIsr will all be empty. This can happen if the sender retires on errors.

Reviewers: Luke Chen <showuon@gmail.com>

clients/src/main/java/org/apache/kafka/common/requests/AlterPartitionRequest.java

@@ -85,12 +85,16 @@ public class AlterPartitionRequest extends AbstractRequest {
             if (version < 3) {
                 data.topics().forEach(topicData -> {
                     topicData.partitions().forEach(partitionData -> {
-                        List<Integer> newIsr = new ArrayList<>(partitionData.newIsrWithEpochs().size());
-                        partitionData.newIsrWithEpochs().forEach(brokerState -> {
-                            newIsr.add(brokerState.brokerId());
-                        });
-                        partitionData.setNewIsr(newIsr);
-                        partitionData.setNewIsrWithEpochs(Collections.emptyList());
+                        // The newIsrWithEpochs will be empty after build. Then we can skip the conversion if the build
+                        // is called again.
+                        if (partitionData.newIsrWithEpochs().size() > 0) {
+                            List<Integer> newIsr = new ArrayList<>(partitionData.newIsrWithEpochs().size());
+                            partitionData.newIsrWithEpochs().forEach(brokerState -> {
+                                newIsr.add(brokerState.brokerId());
+                            });
+                            partitionData.setNewIsr(newIsr);
+                            partitionData.setNewIsrWithEpochs(Collections.emptyList());
+                        }
                     });
                 });
             }

clients/src/test/java/org/apache/kafka/common/requests/AlterPartitionRequestTest.java

@@ -72,5 +72,18 @@ class AlterPartitionRequestTest {
             assertEquals(newIsrWithBrokerEpoch, partitionData.newIsrWithEpochs());
             assertTrue(partitionData.newIsr().isEmpty());
         }
+
+        // Build the request again to make sure build() is idempotent.
+        alterPartitionRequest = builder.build(version);
+        assertEquals(1, alterPartitionRequest.data().topics().size());
+        assertEquals(1, alterPartitionRequest.data().topics().get(0).partitions().size());
+        alterPartitionRequest.data().topics().get(0).partitions().get(0);
+        if (version < 3) {
+            assertEquals(Arrays.asList(1, 2, 3), partitionData.newIsr());
+            assertTrue(partitionData.newIsrWithEpochs().isEmpty());
+        } else {
+            assertEquals(newIsrWithBrokerEpoch, partitionData.newIsrWithEpochs());
+            assertTrue(partitionData.newIsr().isEmpty());
+        }
     }
 }