Fail to decode empty response to a Read operation

[dnav]

Version(s)

2.0.0-SNAPSHOT (leshan.eclipseprojects.io)

Which components

leshan.eclipseprojects.io

Tested With

custom CoAP server

What happened

When performing a Read operation returning an empty response, Leshan returns an "failed to decode" error in some case.

I tested a Read on an empty Object (no Object Instance), an empty Object Instance (no readable Resource, object ID 7), and an empty multiple Resource (no Resource Instance).

The response is always a 2.05 content with or witout a content-format option, and with or without a payload.

Content-format option	payload	Read on Object	Read on Object Instance	Read on Resource Instance
none	none	Error: "Invalid Response: Unable to decode response payload"	Error: "Invalid Response: Unable to decode response payload"	Error: "Invalid Response: Unable to decode response payload"
SenML CBOR	none	Success	Error: "Invalid Response: Unable to decode response payload"	Success
SenML CBOR	0x80 (array of 0 elements)	Success	Error: "Invalid Response: Unable to decode response payload"	Success
SenML JSON	none	Success	Error: "Invalid Response: Unable to decode response payload"	Success
SenML JSON	"[]"	Success	Error: "Invalid Response: Unable to decode response payload"	Success
TLV	none	Success	Success	Success
TLV	0x08 00 00 (empty instance 0)	Success	Success	Success

How to reproduce

No response

Relevant Output

No response

[sbernard31]

Thx for reporting 🙏.

For none content format line, this is the expected behavior for now. We will wait for OMA answer to OpenMobileAlliance/OMA_LwM2M_for_Developers#579 before to change anything.

For Read on Object Instance, I need to investigate as at first sight there is a kind on inconsistency.

[sbernard31]

The Object Instance inconsistent behavior is fixed by #1624.

I let this issue open waiting for the none content format case answer.

[sbernard31]

I integrated #1624 in master. It will be available in sandbox very soon and will be part of next release 2.0.0-M15.

Issue was closed automatically I reopen it because :

I let this issue open waiting for the none content format case answer.

[slaft]

While looking into #1633, I also checked what happens when an empty payload is sent in a Read Response/Observe Response/Notify.

This is what I came across (with Leshan 2.0.0-M15):

• On Object, Object Instance or multiple Resource:
  • JSON -> InvalidResponseException
  • SenML JSON -> success
  • SenML CBOR -> success
• On single Resource or multiple Resource Instance:
  • JSON -> InvalidResponseException
  • SenML JSON -> InvalidResponseException
  • SenML CBOR -> InvalidResponseException
• On a Composite request:
  • SenML JSON -> success
  • SenML CBOR -> success