fable: Add from_json to adl_serializer<sol::object>

Author: cassava

fable/include/fable/utility/sol.hpp

@@ -33,6 +33,7 @@
 
 #include <nlohmann/json.hpp>
 
+#include <sol/state_view.hpp>
 #include <sol/object.hpp>    // for object
 #include <sol/optional.hpp>  // for optional
 #include <sol/table.hpp>     // for table
@@ -58,6 +59,7 @@ namespace nlohmann {
  */
 template <>
 struct adl_serializer<sol::object> {
+  // NOLINTNEXTLINE(misc-no-recursion)
   static void to_json_array(json& j, const sol::table& tbl) {
     if (j.type() != json::value_t::array) {
       j = json::array();
@@ -76,6 +78,7 @@ struct adl_serializer<sol::object> {
     }
   }
 
+  // NOLINTNEXTLINE(misc-no-recursion)
   static void to_json_object(json& j, const sol::table& tbl) {
     if (j.type() != json::value_t::object) {
       j = json::object();
@@ -86,6 +89,7 @@ struct adl_serializer<sol::object> {
     }
   }
 
+  // NOLINTNEXTLINE(misc-no-recursion)
   static void to_json(json& j, const sol::table& tbl) {
     if (tbl.pairs().begin() == tbl.pairs().end()) {
       // We don't know whether this is an empty array or an empty object,
@@ -108,6 +112,7 @@ struct adl_serializer<sol::object> {
     }
   }
 
+  // NOLINTNEXTLINE(misc-no-recursion)
   static void to_json(json& j, const sol::object& obj) {
     switch (obj.get_type()) {
       case sol::type::table: {
@@ -155,6 +160,69 @@ struct adl_serializer<sol::object> {
         break;
     }
   }
+
+  // NOLINTNEXTLINE(misc-no-recursion)
+  static void from_json(const json& j, sol::object& obj) {
+    auto* L = obj.lua_state();
+    if (L == nullptr) {
+      throw std::logic_error("can only deserialize to existing sol::object");
+    }
+    auto lua = sol::state_view(L);
+    switch (j.type()) {
+      case json::value_t::object: {
+        auto tbl = lua.create_table();
+        for (const auto& it : j.items()) {
+          auto tmp = sol::object(L, sol::in_place, nullptr);
+          from_json(it.value(), tmp);
+          tbl[it.key()] = tmp;
+        }
+        obj = tbl;
+        break;
+      }
+      case json::value_t::null: {
+        obj = sol::object(L, sol::in_place, nullptr);
+        break;
+      }
+      case json::value_t::array: {
+        auto tbl = lua.create_table();
+        for (const auto& el : j) {
+          auto tmp = sol::object(L, sol::in_place, nullptr);
+          from_json(el, tmp);
+          tbl.add(tmp);
+        }
+        obj = tbl;
+        break;
+      }
+      case json::value_t::binary: {
+        obj = sol::object(L, sol::in_place, nullptr);
+        break;
+      }
+      case json::value_t::string: {
+        obj = sol::object(L, sol::in_place, j.get<std::string>());
+        break;
+      }
+      case json::value_t::boolean: {
+        obj = sol::object(L, sol::in_place, j.get<bool>());
+        break;
+      }
+      case json::value_t::number_float: {
+        obj = sol::object(L, sol::in_place, j.get<double>());
+        break;
+      }
+      case json::value_t::number_unsigned: {
+        obj = sol::object(L, sol::in_place, j.get<unsigned long>());
+        break;
+      }
+      case json::value_t::number_integer: {
+        obj = sol::object(L, sol::in_place, j.get<signed long>());
+        break;
+      }
+      case json::value_t::discarded: {
+        obj = sol::object(L, sol::in_place, nullptr);
+        break;
+      }
+    }
+  }
 };
 
 }  // namespace nlohmann

fable/src/fable/utility/sol_test.cpp

@@ -46,3 +46,125 @@ TEST(fable_utility_sol, to_json) {
   assert_xeq("x = { extra = true, 1, 2, 3 }", R"([ 1, 2, 3, { "extra": true } ])");
   assert_xeq("x = {}", "[]");
 }
+
+void json_to_lua(sol::state_view& lua, std::string_view field, const fable::Json& json) {
+  auto tmp = sol::object(lua, sol::in_place, nullptr);
+  nlohmann::adl_serializer<sol::object>::from_json(json, tmp);
+  lua[field] = tmp;
+}
+
+TEST(fable_utility_sol, from_json_bool) {
+  auto lua = sol::state();
+  lua.open_libraries(sol::lib::base);
+
+  json_to_lua(lua, "json", Json(true));
+  lua.script(
+  R"(
+    assert(type(json) == "boolean")
+    assert(json == true)
+  )");
+}
+
+TEST(fable_utility_sol, from_json_int) {
+  auto lua = sol::state();
+  lua.open_libraries(sol::lib::base);
+
+  json_to_lua(lua, "json", Json(42));
+  lua.script(
+  R"(
+    assert(type(json) == "number")
+    assert(json == 42)
+  )");
+}
+
+TEST(fable_utility_sol, from_json_float) {
+  auto lua = sol::state();
+  lua.open_libraries(sol::lib::base);
+
+  json_to_lua(lua, "json", Json(3.14159));
+  lua.script(
+  R"(
+    assert(type(json) == "number")
+    assert(json == 3.14159)
+  )");
+}
+
+TEST(fable_utility_sol, from_json_string) {
+  auto lua = sol::state();
+  lua.open_libraries(sol::lib::base);
+
+  json_to_lua(lua, "json", Json("hello world!"));
+  lua.script(
+  R"(
+    assert(type(json) == "string")
+    assert(json == "hello world!")
+  )");
+}
+
+TEST(fable_utility_sol, from_json_array) {
+  auto lua = sol::state();
+  lua.open_libraries(sol::lib::base);
+
+  json_to_lua(lua, "json", Json({1, 2, 3}));
+  lua.script(
+  R"(
+    assert(type(json) == "table")
+    assert(#json == 3)
+    assert(json[1] == 1)
+    assert(json[2] == 2)
+    assert(json[3] == 3)
+  )");
+}
+
+TEST(fable_utility_sol, from_json_object) {
+  auto lua = sol::state();
+  lua.open_libraries(sol::lib::base);
+
+  auto json = Json{
+    {"xbool", true},
+    {"xstring", "hello world!"},
+    {"xint", -42}, // NOLINT
+    {"xunsigned", 42u}, // NOLINT
+    {"xdouble", 42.0}, // NOLINT
+    {"xarray", {1, 2, 3}},
+    {"xobject", {
+      {"foo", "bar"},
+    }},
+    {"xnull", nullptr},
+  };
+
+  auto tmp = sol::object(lua["json"]);
+  nlohmann::adl_serializer<sol::object>::from_json(json, tmp);
+  lua["json"] = tmp;
+  lua.script(
+  R"(
+    print(json)
+    assert(json)
+
+    print(json.xbool)
+    assert(json.xbool == true)
+
+    print(json.xstring)
+    assert(json.xstring == "hello world!")
+
+    print(json.xint)
+    assert(json.xint == -42)
+
+    print(json.xunsigned)
+    assert(json.xunsigned == 42)
+
+    print(json.xdouble)
+    assert(json.xdouble == 42.0)
+
+    assert(type(json.xarray) == "table")
+    assert(json.xarray[1] == 1)
+    assert(json.xarray[3] == 3)
+    assert(json.xarray[4] == nil)
+
+    print(json.xobject)
+    assert(json.xobject)
+    assert(json.xobject.foo == "bar")
+
+    assert(not json.xnull)
+  )");
+}