🚧 conversions for std::optional

test/src/unit-conversions.cpp

@@ -50,6 +50,7 @@ using nlohmann::json;
 #endif
 
 #if defined(JSON_HAS_CPP_17)
+    #include <optional>
     #include <string_view>
 #endif
 
@@ -189,7 +190,6 @@ TEST_CASE("value conversion")
         }
     }
 
-
     SECTION("get an object (implicit)")
     {
         json::object_t o_reference = {{"object", json::object()},
@@ -1575,3 +1575,63 @@ TEST_CASE("JSON to enum mapping")
         CHECK(TS_INVALID == json("what?").get<TaskState>());
     }
 }
+
+#ifdef JSON_HAS_CPP_17
+TEST_CASE("std::optional")
+{
+    SECTION("null")
+    {
+        json j_null;
+        std::optional<std::string> opt_null;
+
+        CHECK(json(opt_null) == j_null);
+        //CHECK(std::optional<std::string>(j_null) == std::nullopt);
+    }
+
+    SECTION("string")
+    {
+        json j_string = "string";
+        std::optional<std::string> opt_string = "string";
+
+        CHECK(json(opt_string) == j_string);
+        CHECK(std::optional<std::string>(j_string) == opt_string);
+    }
+
+    SECTION("bool")
+    {
+        json j_bool = true;
+        std::optional<bool> opt_bool = true;
+
+        CHECK(json(opt_bool) == j_bool);
+        CHECK(std::optional<bool>(j_bool) == opt_bool);
+    }
+
+    SECTION("number")
+    {
+        json j_number = 1;
+        std::optional<int> opt_int = 1;
+
+        CHECK(json(opt_int) == j_number);
+        CHECK(std::optional<int>(j_number) == opt_int);
+    }
+
+    SECTION("array")
+    {
+        json j_array = {1, 2, 3};
+        std::optional<std::vector<int>> opt_array = {{1, 2, 3}};
+
+        CHECK(json(opt_array) == j_array);
+        CHECK(std::optional<std::vector<int>>(j_array) == opt_array);
+    }
+
+    SECTION("object")
+    {
+        json j_object = {{"one", 1}, {"two", 2}};
+        std::map<std::string, int> m {{"one", 1}, {"two", 2}};
+        std::optional<std::map<std::string, int>> opt_object = m;
+
+        CHECK(json(opt_object) == j_object);
+        CHECK(std::optional<std::map<std::string, int>>(j_object) == opt_object);
+    }
+}
+#endif