I think that this sounds really nice:

https://eslint.org/blog/2022/07/interesting-bugs-caught-by-no-constant-binary-expression/

Ecosystem impact:

• fastify/fastify:
  • test/internals/reply.test.js:175:
    • reply.serializer((x) => (customSerializerCalled = true) && JSON.stringify(x))
  • test/internals/reply.test.js:184:
    • const context = { [kReplySerializerDefault]: (x) => (customSerializerCalled = true) && JSON.stringify(x) }

The only affected code is the two lines above, where Fastify is using a little trick to do two things on one line. It could be replaced with e.g.

reply.serializer((x) => { customSerializerCalled = true; return JSON.stringify(x) })

or

reply.serializer((x) => {
  customSerializerCalled = true
  return JSON.stringify(x)
})

(ping @mcollina, since your repo is the affected one)