Fix NPE in batchPoll by returning 200 OK + empty list instead of 204

[nthmost-orkes]

Pull Request type

• Bugfix
• Feature
• Refactoring (no functional changes, no api changes)
• Build related changes
• WHOSUSING.md
• Other (please describe):

Changes in this PR

Fix NPE in batchPoll by returning empty list instead of 204

Problem

The batchPoll endpoint returned 204 No Content when no tasks were available, causing NPE in client libraries that expected a list object.

Solution

Changed TaskResource.batchPoll() to always return 200 OK with an empty list instead of 204 No Content.

So clients always get 200 OK with either:

• A populated list [task1, task2, ...] when tasks are available
• An empty list [] when no tasks are available

Impact

• Fixes HttpEndToEndTest.testAll NPE (issue HTTP status code mismatch between server and clients since PR #69 (broken tests) #602, failure Issue/upgrade to spring (#3828) #1)
• Backward compatible: all SDKs (Java, Go, C#, Python) expect List<Task> type
• Safer for clients: empty list is more predictable than null/no content

Changes

• rest/src/main/java/com/netflix/conductor/rest/controllers/TaskResource.java:73-84

SDK Compatibility Analysis for batchPoll Fix (generated by Claude Code):

Java SDK (java-sdk/conductor-client/src/main/java/com/netflix/conductor/client/http/TaskClient.java:546-561):

• Return type: List
• Expected behavior: Returns List directly from resp.getData()
• Impact: ✅ No negative impact - Already expects a list, will handle empty list correctly

Go SDK (go-sdk/sdk/client/api_task_resource.go:92-93):

• Return type: []model.Task (Go slice)
• Expected behavior: Declares var result []model.Task and unmarshals response into it
• Impact: ✅ No negative impact - Go slices handle empty arrays naturally, JSON unmarshal will create empty slice

C# SDK (csharp-sdk/Conductor/Api/TaskResourceApi.cs:263-267):

• Return type: List
• Expected behavior: Returns List from BatchPollWithHttpInfo
• Impact: ✅ No negative impact - C# List handles empty lists correctly

Python SDK:

• Return type: list[Task]
• Expected behavior: Expects list type from API
• Impact: ✅ No negative impact - Already verified

All four SDKs expect a list/array type from the batchPoll endpoint:

• Java: List
• Go: []model.Task
• C#: List
• Python: list[Task]

[zachsirotto]

Looking forward to this! Thanks so much 👍