[CHA-2716] Ignore null fields (#46)

* fix: ignore null fields

* style: format code

* test: add unit tests for null serialization

Author: mogita

MIGRATION_v5_to_v6.md

@@ -206,6 +206,45 @@ New composition types: `HasOwnUser`, `HasUserCommonFields`, `HasUserPrivacyField
 | `MembershipLevel` | `MembershipLevelResponse` | |
 | `ThreadedComment` | `ThreadedCommentResponse` | |
 
+## JSON Serialization of Optional Fields
+
+Optional (nullable) fields in request objects are now omitted from the JSON body when not set, instead of being sent as explicit `null`. Previously, every unset field was serialized as `null`, which caused the backend to zero out existing values on partial updates.
+
+**Before:**
+```java
+UpdateAppRequest request = UpdateAppRequest.builder()
+    .enforceUniqueUsernames("no")
+    .build();
+// Wire: {"enforce_unique_usernames":"no","webhook_url":null,"multi_tenant_enabled":null,...}
+// Backend: sets enforce_unique_usernames="no", but ALSO resets webhook_url="", multi_tenant_enabled=false, etc.
+```
+
+**After:**
+```java
+UpdateAppRequest request = UpdateAppRequest.builder()
+    .enforceUniqueUsernames("no")
+    .build();
+// Wire: {"enforce_unique_usernames":"no"}
+// Backend: sets enforce_unique_usernames="no", all other fields preserved
+```
+
+Collection fields (lists, maps) are still serialized when set (including as empty `[]`/`{}`), so you can continue to send an empty list to clear a list field. Unset collection fields (`null`) are now also omitted.
+
+**Clearing individual fields:** To explicitly remove or reset a scalar field, use the partial update endpoints with the `unset` parameter instead of sending `null`:
+
+```java
+// Clear custom fields from a user
+client.updateUsersPartial(UpdateUsersPartialRequest.builder()
+    .users(List.of(UpdateUserPartialRequest.builder()
+        .id(userId)
+        .unset(List.of("field_to_clear"))
+        .build()))
+    .build())
+    .execute();
+```
+
+Partial update models (`UpdateUserPartialRequest`, `UpdateMessagePartialRequest`, `UpdateActivityPartialRequest`) support `set` (a map of fields to update) and `unset` (a list of field names to remove).
+
 ## Getting Help
 
 - [Stream documentation](https://getstream.io/docs/)

src/main/java/io/getstream/services/framework/StreamHTTPClient.java

@@ -1,5 +1,6 @@
 package io.getstream.services.framework;
 
+import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.databind.DeserializationFeature;
 import com.fasterxml.jackson.databind.ObjectMapper;
 import com.fasterxml.jackson.databind.SerializationFeature;
@@ -33,6 +34,7 @@ public class StreamHTTPClient {
   private final ObjectMapper objectMapper =
       new ObjectMapper()
           .configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false)
+          .setSerializationInclusion(JsonInclude.Include.NON_NULL)
           .setDateFormat(
               new StdDateFormat()
                   .withColonInTimeZone(true)

src/test/java/io/getstream/BasicTest.java

@@ -155,30 +155,20 @@ private static void createTestChannel() throws Exception {
   }
 
   static void upsertUsers() throws Exception {
+    String id1 = RandomStringUtils.randomAlphabetic(10);
+    String id2 = RandomStringUtils.randomAlphabetic(10);
+    String id3 = RandomStringUtils.randomAlphabetic(10);
+    String id4 = RandomStringUtils.randomAlphabetic(10);
+
     UserRequest testUserRequestObject =
-        UserRequest.builder()
-            .id(RandomStringUtils.randomAlphabetic(10))
-            .name("Gandalf the Grey")
-            .build();
+        UserRequest.builder().id(id1).name("Gandalf " + id1).build();
 
     List<UserRequest> testUsersRequestObjects = new ArrayList<>();
 
     testUsersRequestObjects.add(testUserRequestObject);
-    testUsersRequestObjects.add(
-        UserRequest.builder()
-            .id(RandomStringUtils.randomAlphabetic(10))
-            .name("Frodo Baggins")
-            .build());
-    testUsersRequestObjects.add(
-        UserRequest.builder()
-            .id(RandomStringUtils.randomAlphabetic(10))
-            .name("Frodo Baggins")
-            .build());
-    testUsersRequestObjects.add(
-        UserRequest.builder()
-            .id(RandomStringUtils.randomAlphabetic(10))
-            .name("Samwise Gamgee")
-            .build());
+    testUsersRequestObjects.add(UserRequest.builder().id(id2).name("Frodo " + id2).build());
+    testUsersRequestObjects.add(UserRequest.builder().id(id3).name("Hobbit " + id3).build());
+    testUsersRequestObjects.add(UserRequest.builder().id(id4).name("Samwise " + id4).build());
 
     UpdateUsersRequest updateUsersRequest =
         UpdateUsersRequest.builder()

src/test/java/io/getstream/ChatTestBase.java

@@ -22,13 +22,7 @@ protected List<String> createTestUsers(int n) throws Exception {
     for (int i = 0; i < n; i++) {
       String id = "tu-" + UUID.randomUUID().toString().replace("-", "").substring(0, 16);
       ids.add(id);
-      users.put(
-          id,
-          UserRequest.builder()
-              .id(id)
-              .name("Test User " + id.substring(0, 8))
-              .role("user")
-              .build());
+      users.put(id, UserRequest.builder().id(id).name("Test User " + id).role("user").build());
     }
     client.updateUsers(UpdateUsersRequest.builder().users(users).build()).execute();
     return ids;

src/test/java/io/getstream/ChatUserIntegrationTest.java

@@ -30,7 +30,7 @@ void testUpsertUsers() throws Exception {
     Map<String, UserRequest> users = new HashMap<>();
     for (int i = 0; i < 2; i++) {
       String id = "tu-" + UUID.randomUUID().toString().replace("-", "").substring(0, 16);
-      users.put(id, UserRequest.builder().id(id).name("Test User " + i).role("user").build());
+      users.put(id, UserRequest.builder().id(id).name("Test User " + id).role("user").build());
     }
 
     var resp = client.updateUsers(UpdateUsersRequest.builder().users(users).build()).execute();
@@ -658,7 +658,7 @@ void testUserCustomData() throws Exception {
         userId,
         UserRequest.builder()
             .id(userId)
-            .name("Custom Data User")
+            .name("Custom Data User " + userId)
             .role("user")
             .custom(customData)
             .build());

src/test/java/io/getstream/FeedIntegrationTests.java

@@ -70,10 +70,18 @@ private static void setupEnvironment() throws Exception {
       Map<String, UserRequest> usersMap = new HashMap<>();
       usersMap.put(
           testUserId,
-          UserRequest.builder().id(testUserId).name("Test User 1").role("user").build());
+          UserRequest.builder()
+              .id(testUserId)
+              .name("Test User " + testUserId)
+              .role("user")
+              .build());
       usersMap.put(
           testUserId2,
-          UserRequest.builder().id(testUserId2).name("Test User 2").role("user").build());
+          UserRequest.builder()
+              .id(testUserId2)
+              .name("Test User " + testUserId2)
+              .role("user")
+              .build());
 
       UpdateUsersRequest updateUsersRequest = UpdateUsersRequest.builder().users(usersMap).build();
 

src/test/java/io/getstream/ModerationTest.java

@@ -37,13 +37,22 @@ static void setup() throws Exception {
 
     Map<String, UserRequest> usersMap = new HashMap<>();
     usersMap.put(
-        testUserId, UserRequest.builder().id(testUserId).name("Test User 1").role("user").build());
+        testUserId,
+        UserRequest.builder().id(testUserId).name("Test User " + testUserId).role("user").build());
     usersMap.put(
         testUserId2,
-        UserRequest.builder().id(testUserId2).name("Test User 2").role("user").build());
+        UserRequest.builder()
+            .id(testUserId2)
+            .name("Test User " + testUserId2)
+            .role("user")
+            .build());
     usersMap.put(
         testModeratorId,
-        UserRequest.builder().id(testModeratorId).name("Moderator").role("admin").build());
+        UserRequest.builder()
+            .id(testModeratorId)
+            .name("Moderator " + testModeratorId)
+            .role("admin")
+            .build());
 
     UpdateUsersRequest updateUsersRequest = UpdateUsersRequest.builder().users(usersMap).build();
     client.updateUsers(updateUsersRequest).execute();

src/test/java/io/getstream/StreamHTTPClientTest.java

@@ -2,8 +2,10 @@
 
 import static org.junit.jupiter.api.Assertions.*;
 
+import com.fasterxml.jackson.core.JsonProcessingException;
 import com.fasterxml.jackson.databind.ObjectMapper;
 import io.getstream.models.MessageResponse;
+import io.getstream.models.UpdateAppRequest;
 import io.getstream.services.framework.StreamHTTPClient;
 import java.util.Date;
 import org.junit.jupiter.api.BeforeAll;
@@ -63,6 +65,33 @@ void testUnixNanosecondTimestampParsing() throws Exception {
             expectedDate.getTime(), message.getUpdatedAt().getTime(), message.getUpdatedAt()));
   }
 
+  @Test
+  void testNullFieldsOmittedFromSerialization() throws JsonProcessingException {
+    // Only set one field, leave everything else null
+    UpdateAppRequest request = UpdateAppRequest.builder().enforceUniqueUsernames("no").build();
+
+    String json = objectMapper.writeValueAsString(request);
+
+    // The set field must be present
+    assertTrue(json.contains("\"enforce_unique_usernames\":\"no\""));
+    // Null fields must be omitted, not serialized as null
+    assertFalse(json.contains("null"), "Null fields should be omitted, got: " + json);
+    assertFalse(json.contains("webhook_url"));
+    assertFalse(json.contains("multi_tenant_enabled"));
+  }
+
+  @Test
+  void testCollectionFieldsSerializedWhenSet() throws JsonProcessingException {
+    // An explicitly set empty list should still be serialized
+    UpdateAppRequest request = UpdateAppRequest.builder().grants(new java.util.HashMap<>()).build();
+
+    String json = objectMapper.writeValueAsString(request);
+
+    assertTrue(
+        json.contains("\"grants\":{}"),
+        "Empty collections should be serialized when explicitly set, got: " + json);
+  }
+
   @Test
   void testRFC3339TimestampParsing() throws Exception {
     // Create a JSON response with RFC 3339 formatted timestamp

src/test/java/io/getstream/VideoIntegrationTest.java

@@ -514,8 +514,9 @@ void testUserBlocking() throws Exception {
     String bobId = "vid-bob-blk-" + RandomStringUtils.randomAlphabetic(8).toLowerCase();
 
     Map<String, UserRequest> usersMap = new HashMap<>();
-    usersMap.put(aliceId, UserRequest.builder().id(aliceId).name("Alice Blocker").build());
-    usersMap.put(bobId, UserRequest.builder().id(bobId).name("Bob Blocked").build());
+    usersMap.put(
+        aliceId, UserRequest.builder().id(aliceId).name("Alice Blocker " + aliceId).build());
+    usersMap.put(bobId, UserRequest.builder().id(bobId).name("Bob Blocked " + bobId).build());
     client.updateUsers(UpdateUsersRequest.builder().users(usersMap).build()).execute();
 
     // Block bob from alice's perspective (app-level user block, not call-level)
@@ -699,8 +700,8 @@ void testDeactivateUser() throws Exception {
     String bobId = "vid-bob-" + RandomStringUtils.randomAlphabetic(8).toLowerCase();
 
     Map<String, UserRequest> usersMap = new HashMap<>();
-    usersMap.put(aliceId, UserRequest.builder().id(aliceId).name("Alice Video").build());
-    usersMap.put(bobId, UserRequest.builder().id(bobId).name("Bob Video").build());
+    usersMap.put(aliceId, UserRequest.builder().id(aliceId).name("Alice Video " + aliceId).build());
+    usersMap.put(bobId, UserRequest.builder().id(bobId).name("Bob Video " + bobId).build());
     client.updateUsers(UpdateUsersRequest.builder().users(usersMap).build()).execute();
 
     // Deactivate alice
@@ -917,7 +918,11 @@ void testTeams() throws Exception {
     Map<String, UserRequest> usersMap = new HashMap<>();
     usersMap.put(
         userId,
-        UserRequest.builder().id(userId).name("Teams User").teams(List.of("red", "blue")).build());
+        UserRequest.builder()
+            .id(userId)
+            .name("Teams User " + userId)
+            .teams(List.of("red", "blue"))
+            .build());
     client.updateUsers(UpdateUsersRequest.builder().users(usersMap).build()).execute();
 
     // Create call with team="blue"