From 4fa73b442b87c90854d377c7854e791e8a254b38 Mon Sep 17 00:00:00 2001
From: Timothee Cour <timothee.cour2@gmail.com>
Date: Fri, 5 Jun 2020 02:06:02 -0700
Subject: [PATCH] make toJson more feature complete

---
 lib/pure/json.nim           | 43 +++++++++++++++++++++++++++----------
 tests/stdlib/tjsonmacro.nim | 13 ++++++++++-
 2 files changed, 44 insertions(+), 12 deletions(-)

diff --git a/lib/pure/json.nim b/lib/pure/json.nim
index c682a730896d5..80eb1be4b6845 100644
--- a/lib/pure/json.nim
+++ b/lib/pure/json.nim
@@ -370,20 +370,20 @@ proc `%`*(o: enum): JsonNode =
   ## string. Creates a new ``JString JsonNode``.
   result = %($o)
 
-proc toJson(x: NimNode): NimNode {.compileTime.} =
+proc toJsonImpl(x: NimNode): NimNode {.compileTime.} =
   case x.kind
   of nnkBracket: # array
     if x.len == 0: return newCall(bindSym"newJArray")
     result = newNimNode(nnkBracket)
     for i in 0 ..< x.len:
-      result.add(toJson(x[i]))
+      result.add(toJsonImpl(x[i]))
     result = newCall(bindSym("%", brOpen), result)
   of nnkTableConstr: # object
     if x.len == 0: return newCall(bindSym"newJObject")
     result = newNimNode(nnkTableConstr)
     for i in 0 ..< x.len:
       x[i].expectKind nnkExprColonExpr
-      result.add newTree(nnkExprColonExpr, x[i][0], toJson(x[i][1]))
+      result.add newTree(nnkExprColonExpr, x[i][0], toJsonImpl(x[i][1]))
     result = newCall(bindSym("%", brOpen), result)
   of nnkCurly: # empty object
     x.expectLen(0)
@@ -391,7 +391,7 @@ proc toJson(x: NimNode): NimNode {.compileTime.} =
   of nnkNilLit:
     result = newCall(bindSym"newJNull")
   of nnkPar:
-    if x.len == 1: result = toJson(x[0])
+    if x.len == 1: result = toJsonImpl(x[0])
     else: result = newCall(bindSym("%", brOpen), x)
   else:
     result = newCall(bindSym("%", brOpen), x)
@@ -399,7 +399,7 @@ proc toJson(x: NimNode): NimNode {.compileTime.} =
 macro `%*`*(x: untyped): untyped =
   ## Convert an expression to a JsonNode directly, without having to specify
   ## `%` for every element.
-  result = toJson(x)
+  result = toJsonImpl(x)
 
 proc `==`*(a, b: JsonNode): bool =
   ## Check two nodes for equality
@@ -1264,17 +1264,38 @@ when false:
 # { "json": 5 }
 # To get that we shall use, obj["json"]
 
-proc toJson2*[T](a: T): JsonNode =
-  ## allows custom serialization
+proc isNamedTuple(T: typedesc): bool {.magic: "TypeTrait".}
+
+proc toJson*[T](a: T): JsonNode =
+  ## like `%` but allows custom serialization hook if `serialize(a: T)` is in scope
   when compiles(serialize(a)):
     proc funAdd(t: JsonNode, key: string, val: string) = t[key] = %val
     proc funAdd2(t: JsonNode, key: string, val: JsonNode) = t[key] = val
     proc funObj(): JsonNode = newJObject()
     result = serialize(a, funObj, funAdd, funAdd2)
-  elif T is object:
-    result = newJObject()
-    for k,v in fieldPairs(a):
-      result[k] = toJson2(v)
+  elif T is object | tuple:
+    const isNamed = T is object or isNamedTuple(T)
+    when isNamed:
+      result = newJObject()
+      for k, v in a.fieldPairs: result[k] = toJson(v)
+    else:
+      result = newJArray()
+      for v in a.fields: result.add toJson(v)
+  elif T is ref | ptr:
+    if a == nil: result = newJNull()
+    else: result = toJson(a[])
+  elif T is array | seq:
+    result = newJArray()
+    for ai in a:
+      result.add toJson(ai)
+  elif T is pointer:
+    result = toJson(cast[int](a))
+  elif T is distinct:
+    result = toJson(a.distinctBase)
+  elif T is bool:
+    result = %(a)
+  elif T is Ordinal:
+    result = %(cast[int](a))
   else:
     result = %a
 
diff --git a/tests/stdlib/tjsonmacro.nim b/tests/stdlib/tjsonmacro.nim
index 6bb4be23e41aa..a5a1b53a23208 100644
--- a/tests/stdlib/tjsonmacro.nim
+++ b/tests/stdlib/tjsonmacro.nim
@@ -638,8 +638,19 @@ static:
   testJson()
 
 import strtabs
+
 proc testCustom()=
   var t = {"name": "John", "city": "Monaco"}.newStringTable
-  let s = toJson2(t)
+  let s = toJson(t)
   doAssert $s == """{"mode":"modeCaseSensitive","table":{"city":"Monaco","name":"John"}}"""
+
+proc testToJson() =
+  var t = {"z": "Z", "y": "Y"}.newStringTable
+  type A = ref object
+    a1: string
+  let a = (1.1, "fo", 'x', @[10,11], [true, false], [t,newStringTable()], (foo: 0.5'f32, bar: A(a1: "abc"), bar2: A.default))
+  let j = a.toJson
+  doAssert $j == """[1.1,"fo",120,[10,11],[true,false],[{"mode":"modeCaseSensitive","table":{"y":"Y","z":"Z"}},{"mode":"modeCaseSensitive","table":{}}],{"foo":0.5,"bar":{"a1":"abc"},"bar2":null}]"""
+
 testCustom()
+testToJson()