[Bug]: preserve explicit JSON nulls in value mappings for ListTasks without raising NullPointerExceptions #1207

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1. loveen0111

   added the

   Bug

   issue type on Oct 7, 2026
2. Emryswu commented on Oct 21, 2026

   

   Emryswu

   on Oct 21, 2026

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   Hi, I'd like to take this one.

   I'll first try to reproduce the NPE on the current main with a ListTasks response containing explicit JSON nulls, covering both the JSON-RPC and REST paths. If it still reproduces, I'll open a PR with a regression test, following the same approach as #1174 for GetTask.
3. Emryswu commented on Oct 21, 2026

   

   Emryswu

   on Oct 21, 2026

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   I tried to reproduce this on the latest main (05f5d9b) and couldn't trigger the response-side NPE. Explicit nulls in optional fields, metadata at every level, nested objects and arrays all deserialize fine on both the JSON-RPC and REST paths. The fix from #1174 also seems to be included in 1.4.0.Final already.

   While testing, though, I did hit a separate NPE on the request side when calling listTasks(ListTasksParams.builder().build(), null) on JSONRPCTransport, which leaves the optional tenant unset (null), before any HTTP request is sent:

   java.lang.NullPointerException
       at org.a2aproject.sdk.grpc.ListTasksRequest$Builder.setTenant(ListTasksRequest.java:910)
       at org.a2aproject.sdk.grpc.mapper.ListTasksParamsMapperImpl.toProto(ListTasksParamsMapperImpl.java:44)
       at org.a2aproject.sdk.grpc.utils.ProtoUtils$ToProto.listTasksParams(ProtoUtils.java:104)
       at org.a2aproject.sdk.client.transport.jsonrpc.JSONRPCTransport.listTasks(JSONRPCTransport.java:177)
   

   @loveen0111 could you share the stack trace you're seeing? If it matches this one, I'm happy to open a PR with a regression test for it.
4. Emryswu

   added a commit that references this issue on Oct 21, 2026

   fix(grpc): avoid NPE when listTasks is called without a tenant

   ...

   c899da6
5. kabir

   added a commit that references this issue on Oct 23, 2026

   fix(grpc): avoid NPE when listTasks is called without a tenant (#1240)

   ...

   4e98c62
6. loveen0111 commented on Oct 30, 2026

   

   loveen0111

   on Oct 30, 2026

   Last edited by loveen0111

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   3. I tried to reproduce this on the latest main (05f5d9b) and couldn't trigger the response-side NPE. Explicit nulls in optional fields, metadata at every level, nested objects and arrays all deserialize fine on both the JSON-RPC and REST paths. The fix from #1174 also seems to be included in 1.4.0.Final already.
   While testing, though, I did hit a separate NPE on the request side when calling listTasks(ListTasksParams.builder().build(), null) on JSONRPCTransport, which leaves the optional tenant unset (null), before any HTTP request is sent:
   java.lang.NullPointerException at org.a2aproject.sdk.grpc.ListTasksRequest$Builder.setTenant(ListTasksRequest.java:910) at org.a2aproject.sdk.grpc.mapper.ListTasksParamsMapperImpl.toProto(ListTasksParamsMapperImpl.java:44) at org.a2aproject.sdk.grpc.utils.ProtoUtils$ToProto.listTasksParams(ProtoUtils.java:104) at org.a2aproject.sdk.client.transport.jsonrpc.JSONRPCTransport.listTasks(JSONRPCTransport.java:177)

   [@loveen0111](https://github.com/loveen0111) could you share the stack trace you're seeing? If it matches this one, I'm happy to open a PR with a regression test for it.
   

   Hey @Emryswu thanks for taking a look! Yes this error is familiar to the one ive been seeing.

   I see you've raised a fix for this, correct? I am just waiting until the new release is published with this fix, to confirm from my side that this bug is resolved. Thank you :)
7. Emryswu commented on Oct 31, 2026

   

   Emryswu

   on Oct 31, 2026

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   Yes, the fix is in #1240, merged into main on Oct 23. It isn't in 1.4.0.Final, so it should be available in a release after that. Until then, setting the tenant explicitly (e.g. "") should avoid the NPE.
8. kabir commented on Nov 2, 2026

   

   kabir

   on Nov 2, 2026

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   Hi, we will do a release this week.

   I think it looks like this has been fixed, so I'll close the issue. If this is wrong please reopen it. Thanks!
9. kabir

   closed this as completedon Nov 2, 2026
10. kabir commented on Nov 2, 2026

    

    kabir

    on Nov 2, 2026

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    Actually, I realised I started some work last week to address some remaining issues here #1261
11. kabir

    added a commit that references this issue on Nov 3, 2026

    fix: preserve explicit nulls in data and metadata (#1261)

    ...

    788c1ea