Support for unmarshalling to reference types

[auxym]

Is it planned to implement support for unmarshalling to reference (ref object) types? Example based on the README:

import samson

type User = ref object
    name: string
    age: range[0..high(int)]

let input = """
[
    {"name": "John Doe", age: 25},
    {"name": "Jane Doe", age: 22, timezone: "Europe/Stockholm"}
]
"""

let parsed = fromJson5(input, seq[User])

Currently this fails with : "Unsupported type: User".

[auxym]

I tried a quick (naive) implementation, which at first failed because fieldPairs does not work with refs. I tried my own wrapper for refs, but then that fails somewhere in the hasCustomPragma macro (unexpected node type nnkHiddenDeRef). Here was my attempt:

diff --git a/src/samson.nim b/src/samson.nim
index b11589e..1b41a83 100644
--- a/src/samson.nim
+++ b/src/samson.nim
@@ -14,7 +14,7 @@ export errors
 
 type
 
-  PlainObject = (object) and
+  PlainObject = (object|ref object) and
     (not (Option|Either|Table|OrderedTable|HashSet|OrderedSet|DateTime|Time))
 
   SupportedIntegerTypes = int8|int16|int32|int|int64|uint8|uint16|uint32
@@ -302,6 +302,10 @@ proc dateTimeFromJson(tree: JTree, idx: JnodeIdx,
     else:
       result = parseTime(tree.nodes[idx].strVal, f, local())
 
+iterator fieldPairs[T: ref object](o: var T): (string, var typed) 
+    for f, v in fieldPairs(o[]):
+        yield (f, v)
+
 proc fromJsonImpl(tree: JTree, idx: JNodeIdx, T: typedesc): T =
   template error {.used.} =
     schemaError(T, `$`(tree, idx))

[GULPF]

I usually avoid reference types in Nim and I'm not sure samson should support it. Typically there shouldn't be a reason to use a ref type for serialization/deserialization.

I think you might have hit a compiler bug with you solution, and it seems like there are more compiler issues related to fieldPairs and ref types (I just reported nim-lang/Nim#12523).