support variant to_json

qicosmos · Jul 26, 2023 · 8820159 · 8820159
1 parent dd57369
commit 8820159
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Showing 3 changed files with 52 additions and 25 deletions.
diff --git a/iguana/json_util.hpp b/iguana/json_util.hpp
@@ -116,10 +116,19 @@ template <typename T>
 constexpr inline bool unique_ptr_v =
     is_template_instant_of<std::unique_ptr, std::remove_cvref_t<T>>::value;
 
+template <typename T> struct is_variant : std::false_type {};
+
+template <typename... T>
+struct is_variant<std::variant<T...>> : std::true_type {};
+
+template <typename T>
+constexpr inline bool variant_v = is_variant<std::remove_cvref_t<T>>::value;
+
 template <class T>
 constexpr inline bool non_refletable_v =
     container_v<T> || c_array_v<T> || tuple_v<T> || optional_v<T> ||
-    unique_ptr_v<T> || std::is_fundamental_v<std::remove_cvref_t<T>>;
+    unique_ptr_v<T> || std::is_fundamental_v<std::remove_cvref_t<T>> ||
+    variant_v<T>;
 
 template <typename T>
 constexpr inline bool refletable_v = is_reflection_v<std::remove_cvref_t<T>>;

diff --git a/iguana/json_writer.hpp b/iguana/json_writer.hpp
@@ -12,6 +12,13 @@ template <typename Stream, typename T,
           std::enable_if_t<refletable_v<T>, int> = 0>
 IGUANA_INLINE void to_json(T &&t, Stream &s);
 
+template <typename Stream, typename T>
+IGUANA_INLINE void render_json_value(Stream &ss, std::optional<T> &val);
+
+template <typename Stream, typename T,
+          std::enable_if_t<fixed_array_v<T>, int> = 0>
+IGUANA_INLINE void render_json_value(Stream &ss, const T &t);
+
 template <typename Stream, typename T,
           std::enable_if_t<sequence_container_v<T>, int> = 0>
 IGUANA_INLINE void render_json_value(Stream &ss, const T &v);
@@ -27,6 +34,9 @@ IGUANA_INLINE void render_json_value(Stream &ss, const T &o);
 template <typename Stream, typename T, std::enable_if_t<tuple_v<T>, int> = 0>
 IGUANA_INLINE void render_json_value(Stream &ss, const T &v);
 
+template <typename Stream, typename T, std::enable_if_t<variant_v<T>, int> = 0>
+IGUANA_INLINE void render_json_value(Stream &s, T &&t);
+
 template <typename Stream, typename InputIt, typename T, typename F>
 IGUANA_INLINE void join(Stream &ss, InputIt first, InputIt last, const T &delim,
                         const F &f) {
@@ -120,8 +130,7 @@ IGUANA_INLINE void render_array(Stream &ss, const T &v) {
   ss.push_back(']');
 }
 
-template <typename Stream, typename T,
-          std::enable_if_t<fixed_array_v<T>, int> = 0>
+template <typename Stream, typename T, std::enable_if_t<fixed_array_v<T>, int>>
 IGUANA_INLINE void render_json_value(Stream &ss, const T &t) {
   if constexpr (std::is_same_v<char, std::remove_reference_t<
                                          decltype(std::declval<T>()[0])>>) {
@@ -183,7 +192,7 @@ IGUANA_INLINE void render_json_value(Stream &ss, const T &v) {
   }
 }
 
-template <typename Stream, typename T, std::enable_if_t<tuple_v<T>, int> = 0>
+template <typename Stream, typename T, std::enable_if_t<tuple_v<T>, int>>
 IGUANA_INLINE void render_json_value(Stream &s, T &&t) {
   using U = typename std::decay_t<T>;
   s.push_back('[');
@@ -198,6 +207,11 @@ IGUANA_INLINE void render_json_value(Stream &s, T &&t) {
   s.push_back(']');
 }
 
+template <typename Stream, typename T, std::enable_if_t<variant_v<T>, int>>
+IGUANA_INLINE void render_json_value(Stream &s, T &&t) {
+  std::visit([&s](auto value) { render_json_value(s, value); }, t);
+}
+
 template <typename Stream, typename T, std::enable_if_t<refletable_v<T>, int>>
 IGUANA_INLINE void to_json(T &&t, Stream &s) {
   s.push_back('{');
@@ -210,15 +224,9 @@ IGUANA_INLINE void to_json(T &&t, Stream &s) {
 
              write_json_key(s, i, t);
              s.push_back(':');
-
-             if constexpr (!is_reflection<decltype(v)>::value) {
-               render_json_value(s, t.*v);
-             } else {
-               to_json(t.*v, s);
-             }
-
+             render_json_value(s, t.*v);
              if (Idx < Count - 1)
-               s.push_back(',');
+               IGUANA_LIKELY { s.push_back(','); }
            });
   s.push_back('}');
 }

diff --git a/test/unit_test.cpp b/test/unit_test.cpp
@@ -619,6 +619,12 @@ TEST_CASE("test the string_view") {
     CHECK(*(b.edition) == "invalid number");
   }
   {
+    auto validator = [](book_t b) {
+      CHECK(b.title == "C++ templates");
+      CHECK(*(b.edition) == "invalid number");
+      CHECK(b.author[0] == "David Vandevoorde");
+      CHECK(b.author[1] == "Nicolai M. Josuttis");
+    };
     std::string str = R"({
     "title": "C++ templates",
     "edition": "invalid number",
@@ -628,19 +634,23 @@ TEST_CASE("test the string_view") {
     ]})";
     book_t b;
     iguana::from_json(b, str);
-    CHECK(b.title == "C++ templates");
-    CHECK(*(b.edition) == "invalid number");
-    CHECK(b.author[0] == "David Vandevoorde");
-    CHECK(b.author[1] == "Nicolai M. Josuttis");
-
-    std::string ss;
-    iguana::to_json(b, ss);
-    book_t b1;
-    iguana::from_json(b1, str);
-    CHECK(b1.title == "C++ templates");
-    CHECK(*(b1.edition) == "invalid number");
-    CHECK(b1.author[0] == "David Vandevoorde");
-    CHECK(b1.author[1] == "Nicolai M. Josuttis");
+    validator(b);
+    {
+      std::string ss;
+      iguana::to_json(b, ss);
+      book_t b1;
+      iguana::from_json(b1, ss);
+      validator(b1);
+    }
+    {
+      // test variant
+      std::variant<int, book_t> vb = b;
+      std::string ss;
+      iguana::to_json(vb, ss);
+      book_t b1;
+      iguana::from_json(b1, ss);
+      validator(b1);
+    }
   }
   {
     std::string str = R"(["tom", 30, 25.8])";