Fix Paginator dropping results on empty pages (DECO-27280)

databricks-sdk-java/src/main/java/com/databricks/sdk/service/iam/AccountGroupsAPI.java

@@ -71,6 +71,9 @@ public Iterable<Group> list(ListAccountGroupsRequest request) {
             impl::list,
             ListGroupsResponse::getResources,
             response -> {
+              if (response.getResources() == null || response.getResources().isEmpty()) {
+                return null;
+              }
               Long offset = request.getStartIndex();
               if (offset == null) {
                 offset = 0L;

databricks-sdk-java/src/main/java/com/databricks/sdk/service/iam/AccountServicePrincipalsAPI.java

@@ -64,6 +64,9 @@ public Iterable<ServicePrincipal> list(ListAccountServicePrincipalsRequest reque
             impl::list,
             ListServicePrincipalResponse::getResources,
             response -> {
+              if (response.getResources() == null || response.getResources().isEmpty()) {
+                return null;
+              }
               Long offset = request.getStartIndex();
               if (offset == null) {
                 offset = 0L;

databricks-sdk-java/src/main/java/com/databricks/sdk/service/iam/AccountUsersAPI.java

@@ -74,6 +74,9 @@ public Iterable<User> list(ListAccountUsersRequest request) {
             impl::list,
             ListUsersResponse::getResources,
             response -> {
+              if (response.getResources() == null || response.getResources().isEmpty()) {
+                return null;
+              }
               Long offset = request.getStartIndex();
               if (offset == null) {
                 offset = 0L;

databricks-sdk-java/src/main/java/com/databricks/sdk/service/iam/GroupsAPI.java

@@ -68,6 +68,9 @@ public Iterable<Group> list(ListGroupsRequest request) {
             impl::list,
             ListGroupsResponse::getResources,
             response -> {
+              if (response.getResources() == null || response.getResources().isEmpty()) {
+                return null;
+              }
               Long offset = request.getStartIndex();
               if (offset == null) {
                 offset = 0L;

databricks-sdk-java/src/main/java/com/databricks/sdk/service/iam/ServicePrincipalsAPI.java

@@ -64,6 +64,9 @@ public Iterable<ServicePrincipal> list(ListServicePrincipalsRequest request) {
             impl::list,
             ListServicePrincipalResponse::getResources,
             response -> {
+              if (response.getResources() == null || response.getResources().isEmpty()) {
+                return null;
+              }
               Long offset = request.getStartIndex();
               if (offset == null) {
                 offset = 0L;

databricks-sdk-java/src/main/java/com/databricks/sdk/service/iam/UsersAPI.java

@@ -87,6 +87,9 @@ public Iterable<User> list(ListUsersRequest request) {
             impl::list,
             ListUsersResponse::getResources,
             response -> {
+              if (response.getResources() == null || response.getResources().isEmpty()) {
+                return null;
+              }
               Long offset = request.getStartIndex();
               if (offset == null) {
                 offset = 0L;

databricks-sdk-java/src/main/java/com/databricks/sdk/support/Paginator.java

@@ -1,6 +1,7 @@
 package com.databricks.sdk.support;
 
 import java.util.Collection;
+import java.util.Collections;
 import java.util.Iterator;
 import java.util.function.Function;
 
@@ -52,19 +53,27 @@ public Paginator(
   }
 
   private boolean flipNextPage(RQ request, boolean firstRequest) {
-    if (!firstRequest && request == null) {
-      return false;
-    }
-    response = requestFn.apply(request);
-    if (response == null) {
-      return false;
-    }
-    Collection<T> results = itemsFn.apply(response);
-    if (results == null) {
-      return false;
+    // A page may be empty while still carrying a next-page token (e.g. when
+    // leading items are filtered out server-side), so an empty page must not
+    // stop iteration on its own. Termination is governed solely by nextPageFn
+    // returning null, which signals that no further pages exist.
+    while (firstRequest || request != null) {
+      response = requestFn.apply(request);
+      if (response == null) {
+        return false;
+      }
+      Collection<T> results = itemsFn.apply(response);
+      if (results == null) {
+        results = Collections.emptyList();
+      }
+      currentPage = results.iterator();
+      if (currentPage.hasNext()) {
+        return true;
+      }
+      request = nextPageFn.apply(response);
+      firstRequest = false;
     }
-    currentPage = results.iterator();
-    return currentPage.hasNext();
+    return false;
   }
 
   private Iterator<T> outerIterator() {