Roundtrip fails when used on Table with case object as key

[yuanweixin]

So, if I

1. define a case object
2. use the case object as key in a Table
3. serialize the table
4. deserialize the table

The code fails at step 4 because it represents the key as a json object.

In example below, the generated json is:
{{"kind":"TermS","term":42}:42}

Can user expect the default json ser/deser to cover such a use case? If not, what's the correct way to use the library so that roundtripping works?

import jsony, tables, hashes

type SymbolKind* {.pure.} = enum
  TermS

type Symbol* = object
  case kind*: SymbolKind
  of SymbolKind.TermS:
    term*: int

proc hash*(x: Symbol): Hash =
  var h: Hash = 0
  h = h !& hash(x.kind)
  case x.kind 
  of TermS:
    h = h !& hash(x.term)
  else:
    discard
  return !$h

proc `==`*(a,b: Symbol) : bool = 
  return a.kind == b.kind and a.term == b.term

var t : Table[Symbol, int]

t[Symbol(kind: TermS, term: 42)] = 42

let str = t.toJson()
echo str
discard str.fromJson(Table[Symbol, int])

[pietroppeter]

Not the maintainer, here are my thoughts

Can user expect the default json ser/deser to cover such a use case?

No, since json keys must be string (yaml keys can be pretty much anything instead)

If not, what's the correct way to use the library so that roundtripping works?

I would say the library could decide not to allow cases like these. I am not even sure how jsony by itself is working on serializing the table to json (did you add a custom dumpHook?). There are generic dumpHooks for objects and ref objects but I am not sure if they are supposed to work like that. I guess in principle one can define in the library a dumpHook for a generic table constraining the key not to be string or enum and raising an error...

[yuanweixin]

|> did you add a custom dumpHook?

nope, see the repro code. that's all it takes.

|> No, since json keys must be string (yaml keys can be pretty much anything instead)

well yes, I get that json syntax disallows such constructs. what I was getting at is, it is inconsistent for the library to allow serialize but fails to deserialize an input.

[treeform]

This looks like a bug. It should not create invalid JSON. I'll add a check to make sure keys are always strings or give a compile time error.