Interpret JsonExtensionData (#261)

WoofWare.Myriad.Plugins/JsonSerializeGenerator.fs

@@ -146,6 +146,7 @@ module internal JsonSerializeGenerator =
                 ]
             |> SynExpr.createLambda "field"
             |> fun e -> e, false
+        | JsonNode -> SynExpr.createIdent "id", true
         | _ ->
             // {type}.toJsonNode
             let typeName =
@@ -187,6 +188,14 @@ module internal JsonSerializeGenerator =
             sb.ToString () |> SynExpr.CreateConst
         | Some name -> name.ArgExpr
 
+    let getIsJsonExtension (attrs : SynAttribute list) : bool =
+        attrs
+        |> List.tryFind (fun attr ->
+            (SynLongIdent.toString attr.TypeName)
+                .EndsWith ("JsonExtensionData", StringComparison.Ordinal)
+        )
+        |> Option.isSome
+
     /// `populateNode` will be inserted before we return the `node` variable.
     ///
     /// That is, we give you access to a `JsonObject` called `node`,
@@ -256,7 +265,31 @@ module internal JsonSerializeGenerator =
         fields
         |> List.map (fun fieldData ->
             let propertyName = getPropertyName fieldData.Ident fieldData.Attrs
-            createSerializeRhsRecord propertyName fieldData.Ident fieldData.Type
+            let isJsonExtension = getIsJsonExtension fieldData.Attrs
+
+            if isJsonExtension then
+                let valType =
+                    match fieldData.Type with
+                    | DictionaryType (String, v) -> v
+                    | _ -> failwith "Expected JsonExtensionData to be a Dictionary<string, something>"
+
+                let serialise = fst (serializeNode valType)
+
+                SynExpr.createIdent "node"
+                |> SynExpr.callMethodArg
+                    "Add"
+                    (SynExpr.tuple
+                        [
+                            SynExpr.createIdent "key"
+                            SynExpr.applyFunction serialise (SynExpr.createIdent "value")
+                        ])
+                |> SynExpr.createForEach
+                    (SynPat.identWithArgs
+                        [ Ident.create "KeyValue" ]
+                        (SynArgPats.create [ SynPat.named "key" ; SynPat.named "value" ]))
+                    (SynExpr.createLongIdent' [ Ident.create "input" ; fieldData.Ident ])
+            else
+                createSerializeRhsRecord propertyName fieldData.Ident fieldData.Type
         )
         |> SynExpr.sequential
         |> fun expr -> SynExpr.Do (expr, range0)