Elasticsearch: invalid empty json on 404 INDEX/_doc/ID/_source

[exe-dealer]

GET /existing-index/_doc/notexisting-id/_source
returns empty body when document is not found.
Empty string is invalid json but content-type of response is application/json; charset=UTF-8
it whould be better if response body will be null to make json parser happy

[exe-dealer]

elasticsearch version 6.4

[elasticmachine]

Pinging @elastic/es-core-infra

[original-brownbear]

@jasontedor marked this as "discuss", but I think this should be a bug. Empty body is not a valid return for the json content type (even if it's a 404). "null" sounds like a better choice here.

[danielmitterdorfer]

We discussed this in the core-infra team meeting and want to do the following:

• If the document is not found, raise a resource not found exception and return this as a proper JSON body
• If source is disabled also raise an exception and return this as a proper JSON body.

[cbismuth]

I'd like to have a look at this one.

[cbismuth]

cURL recreation script created in this Gist.

[nik9000]

I'd like to have a look at this one.

Enjoy!

[cbismuth]

PR is open, see https://github.com/elastic/elasticsearch/pull/34083.

I've built on top of the previous behavior. This means we don't make a difference when source is disabled or document is missing: in both cases a ResourceNotFoundException is raised with the same JSON message.
Do you think a difference should be made?