Add support for serialization flavors

json_serialization/reader.nim

@@ -11,7 +11,7 @@ export
   types, errors
 
 type
-  JsonReader* = object
+  JsonReader*[Flavor = DefaultFlavor] = object
     lexer*: JsonLexer
     allowUnknownFields: bool
 
@@ -176,7 +176,11 @@ proc parseJsonNode(r: var JsonReader): JsonNode =
     r.lexer.next()
     if r.lexer.tok != tkCurlyRi:
       while r.lexer.tok == tkString:
-        r.readJsonNodeField(result.fields.mgetOrPut(r.lexer.strVal, nil))
+        r.readJsonNodeField(
+          try:
+            result.fields.mgetOrPut(r.lexer.strVal, nil)
+          except KeyError:
+            raiseAssert "mgetOrPut should never raise a KeyError")
         if r.lexer.tok == tkComma:
           r.lexer.next()
         else:
@@ -368,6 +372,7 @@ template isCharArray(v: auto): bool = false
 proc readValue*[T](r: var JsonReader, value: var T)
                   {.raises: [SerializationError, IOError, Defect].} =
   mixin readValue
+  type ReaderType = type r
 
   let tok {.used.} = r.lexer.tok
 
@@ -495,7 +500,7 @@ proc readValue*[T](r: var JsonReader, value: var T)
     r.skipToken tkCurlyLe
 
     when T.totalSerializedFields > 0:
-      let fields = T.fieldReadersTable(JsonReader)
+      let fields = T.fieldReadersTable(ReaderType)
       var expectedFieldPos = 0
       while r.lexer.tok == tkString:
         when T is tuple:

json_serialization/writer.nim

@@ -9,7 +9,7 @@ type
     RecordStarted
     AfterField
 
-  JsonWriter* = object
+  JsonWriter*[Flavor = DefaultFlavor] = object
     stream*: OutputStream
     hasTypeAnnotations: bool
     hasPrettyOutput*: bool # read-only
@@ -19,13 +19,13 @@ type
 export
   JsonString
 
-proc init*(T: type JsonWriter, stream: OutputStream,
-           pretty = false, typeAnnotations = false): T =
-  result.stream = stream
-  result.hasPrettyOutput = pretty
-  result.hasTypeAnnotations = typeAnnotations
-  result.nestingLevel = if pretty: 0 else: -1
-  result.state = RecordExpected
+proc init*(W: type JsonWriter, stream: OutputStream,
+           pretty = false, typeAnnotations = false): W =
+  W(stream: stream,
+    hasPrettyOutput: pretty,
+    hasTypeAnnotations: typeAnnotations,
+    nestingLevel: if pretty: 0 else: -1,
+    state: RecordExpected)
 
 proc beginRecord*(w: var JsonWriter, T: type)
 proc beginRecord*(w: var JsonWriter)
@@ -228,7 +228,7 @@ proc toJson*(v: auto, pretty = false, typeAnnotations = false): string =
   mixin writeValue
 
   var s = memoryOutput()
-  var w = JsonWriter.init(s, pretty, typeAnnotations)
+  var w = JsonWriter[DefaultFlavor].init(s, pretty, typeAnnotations)
   w.writeValue v
   return s.getOutput(string)
 

tests/test_json_flavor.nim

@@ -0,0 +1,41 @@
+import
+  strutils,
+  serialization,
+  ../json_serialization
+
+Json.createFlavor StringyJson
+
+proc writeValue*(w: var JsonWriter[StringyJson], val: SomeInteger) =
+  writeValue(w, $val)
+
+proc readValue*(r: var JsonReader[StringyJson], v: var SomeSignedInt) =
+  try:
+    v = type(v) parseBiggestInt readValue(r, string)
+  except ValueError as err:
+    r.raiseUnexpectedValue("A signed integer encoded as string")
+
+proc readValue*(r: var JsonReader[StringyJson], v: var SomeUnsignedInt) =
+  try:
+    v = type(v) parseBiggestUInt readValue(r, string)
+  except ValueError as err:
+    r.raiseUnexpectedValue("An unsigned integer encoded as string")
+
+type
+  Container = object
+    name: string
+    x: int
+    y: uint64
+    list: seq[int64]
+
+let c = Container(name: "c", x: -10, y: 20, list: @[1'i64, 2, 25])
+let encoded = StringyJson.encode(c)
+echo "Encoded: ", encoded
+
+let decoded = try:
+  StringyJson.decode(encoded, Container)
+except SerializationError as err:
+  echo err.formatMsg("<encoded>")
+  quit 1
+
+echo "Decoded: ", decoded
+