# HG changeset patch
# User jbe
# Date 1406905919 -7200
# Node ID a8316439035518b6ad75438a09d76bd85af1df41
# Parent  ce208edffcc9b12e3cadfb46bfa3ce59b2dbe091
Allow json.object and json.array functions to convert any Lua value using __pairs and __ipairs metamethods

diff -r ce208edffcc9 -r a83164390355 libraries/json/json.c
--- a/libraries/json/json.c	Fri Aug 01 16:40:10 2014 +0200
+++ b/libraries/json/json.c	Fri Aug 01 17:11:59 2014 +0200
@@ -45,6 +45,8 @@
 #define json_convert_iterator_idx 2
 #define json_convert_output_idx 3
 #define json_convert_shadow_idx 4
+#define json_convert_iterfun_idx 5
+#define json_convert_itertbl_idx 6
 
 // converts a Lua table to a  JSON object or JSON array:
 // (does never modify the argument, returns an empty object or array if argument is nil)
@@ -112,8 +114,26 @@
         }
       }
     } else {
-      // TODO: implement conversion using iterator metamethods
-      return luaL_error(L, "Using %s metamethod not implemented yet", array ? "__ipairs" : "__pairs");
+      // if there is an iterator function,
+      // call iterator function with source value (first argument)
+      // and store 3 result values on stack positions 5 through 7:
+      lua_pushvalue(L, json_convert_iterator_idx);
+      lua_pushvalue(L, 1);
+      lua_call(L, 1, 3);
+      while (1) {
+        lua_pushvalue(L, json_convert_iterfun_idx);
+        lua_pushvalue(L, json_convert_itertbl_idx);
+        lua_pushvalue(L, -3);
+        lua_remove(L, -4);
+        lua_call(L, 2, 2);
+        if (lua_isnil(L, -2)) break;
+        if (lua_type(L, -2) == (array ? LUA_TNUMBER : LUA_TSTRING)) {
+          lua_pushvalue(L, -2);
+          lua_pushvalue(L, -2);
+          lua_rawset(L, json_convert_shadow_idx);
+        }
+        lua_pop(L, 1);
+      }
     }
     // let result table be on top of stack:
     lua_settop(L, json_convert_output_idx);
@@ -740,6 +760,8 @@
 // returns a triple such that 'for key, value in pairs(obj) do ... end'
 // iterates through all key value pairs (including JSON null keys represented as Lua nil):
 static int json_pairs(lua_State *L) {
+  // require one argument to function
+  luaL_checkany(L, 1);
   // return triple of function json_pairs_iterfunc, first argument, and nil:
   lua_pushcfunction(L, json_pairs_iterfunc);
   lua_pushvalue(L, 1);
@@ -775,6 +797,8 @@
 // returns a triple such that 'for idx, value in ipairs(ary) do ... end'
 // iterates through all values (including JSON null represented as Lua nil):
 static int json_ipairs(lua_State *L) {
+  // require one argument to function
+  luaL_checkany(L, 1);
   // return triple of function json_ipairs_iterfunc, first argument, and zero:
   lua_pushcfunction(L, json_ipairs_iterfunc);
   lua_pushvalue(L, 1);