Nim: JSON unmarshalling drops seq's items

[nhanb]

The to macro drops the seq items when I try to unmarshall a recursive type:

Example

import sequtils, json

type
  ContentNodeKind* = enum
    P,
    Br,
    Text,
  ContentNode* = object
    case kind*: ContentNodeKind
    of P: pChildren*: seq[ContentNode]
    of Br: nil
    of Text: textStr*: string

let mynode = ContentNode(kind: P, pChildren: @[
  ContentNode(kind: Text, textStr: "mychild"),
  ContentNode(kind: Br)
])

echo "Original: " & $mynode

let jsonNode = %*mynode
echo "jsonNode: " & $jsonNode
echo "Reversed: " & $jsonNode.to(ContentNode)

Current Output

Original: (kind: P, pChildren: @[(kind: Text, textStr: "mychild"), (kind: Br)])
jsonNode: {"kind":"P","pChildren":[{"kind":"Text","textStr":"mychild"},{"kind":"Br"}]}
Reversed: (kind: P, pChildren: @[])

Expected Output

Original: (kind: P, pChildren: @[(kind: Text, textStr: "mychild"), (kind: Br)])
jsonNode: {"kind":"P","pChildren":[{"kind":"Text","textStr":"mychild"},{"kind":"Br"}]}
Reversed: (kind: P, pChildren: @[(kind: Text, textStr: "mychild"), (kind: Br)])

$ nim --version
Nim Compiler Version 1.0.6 [Linux: amd64]
Compiled at 2020-01-23
Copyright (c) 2006-2019 by Andreas Rumpf

active boot switches: -d:release

[kaushalmodi]

I confirm the issue: https://play.nim-lang.org/#ix=1Kjl

Though it seems to happen when using case objects. When using normal objects, it works fine: https://play.nim-lang.org/#ix=1Kjm

[krux02]

I can't reproduce the issue on my computer, my output is:

Original: (kind: P, pChildren: @[(kind: Text, textStr: "mychild"), (kind: Br)])
jsonNode: {"kind":"P","pChildren":[{"kind":"Text","textStr":"mychild"},{"kind":"Br"}]}
Reversed: (kind: P, pChildren: @[(kind: Text, textStr: "mychild"), (kind: Br)])

nim --version
Nim Compiler Version 1.1.1 [Linux: amd64]
Compiled at 2020-02-26
Copyright (c) 2006-2019 by Andreas Rumpf

git hash: e4ed19c12fcce046d990a918800d9031706e8b66
active boot switches: -d:release -d:danger

[kaushalmodi]

@krux02 It didn't occur to me to try it out on devel.. Indeed this issue cannot be reproduced on the devel branch. The exact same code as in https://play.nim-lang.org/#ix=1Kjl gives the below output on devel:

Hint: /home/kmodi/temp/foo  [Exec]
Nim object: (kind: P, pChildren: @[(kind: Text, textStr: "mychild"), (kind: Br)])
object->JsonNode: {"kind":"P","pChildren":[{"kind":"Text","textStr":"mychild"},{"kind":"Br"}]}
JsonNode->object: (kind: P, pChildren: @[(kind: Text, textStr: "mychild"), (kind: Br)])
@[(kind: Text, textStr: "mychild"), (kind: Br)]
@[(kind: Text, textStr: "mychild"), (kind: Br)]

[krux02]

Then I am closing this as resolved.

[kaushalmodi]

Should this have been closed after adding a test in this category (case objects + JSON set/deser) if one doesn't exist?

[krux02]

Don't know. My guess would be, somebody actively fixed this bug and already added a test for it.

[timotheecour]

I agree, a test should be added before closing this (unless we can point here to an existing test)

[krux02]

@timotheecour ok you convinced me. Then please check the tests if there is a test case already existent. If not integrate a test in the existing test environment.