Returning `undefined` from service's method, always get 404 HTTP Status instead of 204

[Thammachart]

Steps to reproduce

I've created an reproducible repo here: https://github.com/Thammachart/feathersjs-204-issue

• Created the feathersjs Project using feathers g app, with @feathersjs/cli version 4.2.4
  • Choices were Javascript, Yarn, REST API only, Mocha + Assert, No Authentication
• Created Service, in the example repo, svc1
  • Choices were A custom service, svc1, /svc1
• Created service's methods for multiple cases, see the link
• Run yarn start
• Using curl localhost:3030/svc1 with multiple flags like -XGET, -XPOST, -XPATCH, -XDELETE to test each case in each service's method

Expected behavior

• Any methods that return undefined or null should response with 204 No Content HTTP Status Code

Actual behavior

• methods returning undefined implicitly or explicitly, response with the 404 Not Found HTTP Status Code, even though the method exists and got to run properly (console.log in methods run properly)
• methods returning null work as expected
• Interesting Note 1: methods returning boolean false response with 204 No Content HTTP Status Code
• Interesting Note 2: methods returning boolean true response with 2xx HTTP Status Code with content of literal true

I don't know if there is underlying convention behind this. I've checked the Docs, FAQ to no avail.

System configuration

Module versions (especially the part that's not working):

• @feathersjs/feathers ^4.3.11
• @feathersjs/express ^4.3.11
• The rest can be seen at this link

NodeJS version: 12.13.1 from nvm

Operating System: Arch Linux, Kernel 5.4.3-arch1-1

Browser Version: curl 7.67.0

[daffl]

Yes, the return value should be null. It's tested at https://github.com/feathersjs/feathers/blob/master/packages/express/test/rest.test.js#L519 (service at https://github.com/feathersjs/feathers/blob/master/packages/express/test/rest.test.js#L467). Not entirely sure where the best place for it would be in the docs.

[Thammachart]

Ok then,

• what about undefined? Should it be treated differently than null ? For me, in the context of response payload, there is no difference, and undefined is easily a pitfall, when you forget to return
• what about boolean true/false inconsistency?

[dor-benatia]

Is this behavior still happen ? should we return 'undefined' or 'void' ? only 'null' ?