Add macros NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_DEFAULT and ..._NON_INTRUSIVE_WITH_DEFAULT

doc/mkdocs/docs/features/arbitrary_types.md

@@ -85,37 +85,39 @@ Some important things:
 
 If you just want to serialize/deserialize some structs, the `to_json`/`from_json` functions can be a lot of boilerplate.
 
-There are two macros to make your life easier as long as you (1) want to use a JSON object as serialization and (2) want to use the member variable names as object keys in that object:
+There are four macros to make your life easier as long as you (1) want to use a JSON object as serialization and (2) want to use the member variable names as object keys in that object:
 
-- `NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE(name, member1, member2, ...)` is to be defined inside the namespace of the class/struct to create code for.
-- `NLOHMANN_DEFINE_TYPE_INTRUSIVE(name, member1, member2, ...)` is to be defined inside the class/struct to create code for. This macro can also access private members.
+- `NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE(name, member1, member2, ...)` is to be defined inside the namespace of the class/struct to create code for. It will throw an exception in `from_json()` due to a missing value in the JSON object.
+- `NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_WITH_DEFAULT(name, member1, member2, ...)` is to be defined inside the namespace of the class/struct to create code for. It will not throw an exception in `from_json()` due to a missing value in the JSON object, but fills in values from object which is default-constructed by the type.
+- `NLOHMANN_DEFINE_TYPE_INTRUSIVE(name, member1, member2, ...)` is to be defined inside the class/struct to create code for. This macro can also access private members. It will throw an exception in `from_json()` due to a missing value in the JSON object.
+- `NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_DEFAULT(name, member1, member2, ...)` is to be defined inside the class/struct to create code for. This macro can also access private members. It will not throw an exception in `from_json()` due to a missing value in the JSON object, but fills in values from object which is default-constructed by the type.
 
-In both macros, the first parameter is the name of the class/struct, and all remaining parameters name the members.
+In all macros, the first parameter is the name of the class/struct, and all remaining parameters name the members. You can read more docs about them starting from [here](macros.md#nlohmann_define_type_intrusivetype-member).
 
 !!! note
 
- At most 64 member variables can be passed to `NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE` or `NLOHMANN_DEFINE_TYPE_INTRUSIVE`.
+ At most 64 member variables can be passed to these macros.
 
 ??? example
 
  The `to_json`/`from_json` functions for the `person` struct above can be created with:
- 
+
  ```cpp
  namespace ns {
  NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE(person, name, address, age)
  }
  ```
- 
+
  Here is an example with private members, where `NLOHMANN_DEFINE_TYPE_INTRUSIVE` is needed:
- 
+
  ```cpp
  namespace ns {
  class address {
  private:
  std::string street;
  int housenumber;
  int postcode;
- 
+
  public:
  NLOHMANN_DEFINE_TYPE_INTRUSIVE(address, street, housenumber, postcode)
  };

doc/mkdocs/docs/features/macros.md

@@ -186,12 +186,12 @@ When defined to `0`, implicit conversions are switched off. By default, implicit
 ??? example
 
  This is an example for an implicit conversion:
- 
+
  ```cpp
  json j = "Hello, world!";
  std::string s = j;
  ```
- 
+
  When `JSON_USE_IMPLICIT_CONVERSIONS` is defined to `0`, the code above does no longer compile. Instead, it must be
  written like this:
 
@@ -220,6 +220,10 @@ The first parameter is the name of the class/struct, and all remaining parameter
 
 See [Simplify your life with macros](arbitrary_types.md#simplify-your-life-with-macros) for an example.
 
+## `NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_DEFAULT(type, member...)`
+
+This macro is similar to `NLOHMANN_DEFINE_TYPE_INTRUSIVE`. It will not throw an exception in `from_json()` due to a missing value in the JSON object, but can throw due to a mismatched type. In order to support that it requires that the type be default constructible. The `from_json()` function default constructs an object and uses its values as the defaults when calling the `value()` function.
+
 ## `NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE(type, member...)`
 
 This macro can be used to simplify the serialization/deserialization of types if (1) want to use a JSON object as
@@ -231,6 +235,10 @@ first parameter is the name of the class/struct, and all remaining parameters na
 
 See [Simplify your life with macros](arbitrary_types.md#simplify-your-life-with-macros) for an example.
 
+## `NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_WITH_DEFAULT(type, member...)`
+
+This macro is similar to `NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE`. It will not throw an exception in `from_json()` due to a missing value in the JSON object, but can throw due to a mismatched type. In order to support that it requires that the type be default constructible. The `from_json()` function default constructs an object and uses its values as the defaults when calling the `value()` function.
+
 ## `NLOHMANN_JSON_SERIALIZE_ENUM(type, ...)`
 
 This macro simplifies the serialization/deserialization of enum types. See

include/nlohmann/detail/macro_scope.hpp

@@ -334,6 +334,7 @@
 
 #define NLOHMANN_JSON_TO(v1) nlohmann_json_j[#v1] = nlohmann_json_t.v1;
 #define NLOHMANN_JSON_FROM(v1) nlohmann_json_j.at(#v1).get_to(nlohmann_json_t.v1);
+#define NLOHMANN_JSON_FROM_WITH_DEFAULT(v1) nlohmann_json_t.v1 = nlohmann_json_j.value(#v1, nlohmann_json_default_obj.v1);
 
 /*!
 @brief macro
@@ -344,6 +345,10 @@
  friend void to_json(nlohmann::json& nlohmann_json_j, const Type& nlohmann_json_t) { NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_PASTE(NLOHMANN_JSON_TO, __VA_ARGS__)) } \
  friend void from_json(const nlohmann::json& nlohmann_json_j, Type& nlohmann_json_t) { NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_PASTE(NLOHMANN_JSON_FROM, __VA_ARGS__)) }
 
+#define NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_DEFAULT(Type, ...) \
+ friend void to_json(nlohmann::json& nlohmann_json_j, const Type& nlohmann_json_t) { NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_PASTE(NLOHMANN_JSON_TO, __VA_ARGS__)) } \
+ friend void from_json(const nlohmann::json& nlohmann_json_j, Type& nlohmann_json_t) { Type nlohmann_json_default_obj; NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_PASTE(NLOHMANN_JSON_FROM_WITH_DEFAULT, __VA_ARGS__)) }
+
 /*!
 @brief macro
 @def NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE
@@ -353,6 +358,10 @@
  inline void to_json(nlohmann::json& nlohmann_json_j, const Type& nlohmann_json_t) { NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_PASTE(NLOHMANN_JSON_TO, __VA_ARGS__)) } \
  inline void from_json(const nlohmann::json& nlohmann_json_j, Type& nlohmann_json_t) { NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_PASTE(NLOHMANN_JSON_FROM, __VA_ARGS__)) }
 
+#define NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_WITH_DEFAULT(Type, ...) \
+ inline void to_json(nlohmann::json& nlohmann_json_j, const Type& nlohmann_json_t) { NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_PASTE(NLOHMANN_JSON_TO, __VA_ARGS__)) } \
+ inline void from_json(const nlohmann::json& nlohmann_json_j, Type& nlohmann_json_t) { Type nlohmann_json_default_obj; NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_PASTE(NLOHMANN_JSON_FROM_WITH_DEFAULT, __VA_ARGS__)) }
+
 
 // inspired from https://stackoverflow.com/a/26745591
 // allows to call any std function as if (e.g. with begin):

single_include/nlohmann/json.hpp

@@ -2631,6 +2631,7 @@ using is_detected_convertible =
 
 #define NLOHMANN_JSON_TO(v1) nlohmann_json_j[#v1] = nlohmann_json_t.v1;
 #define NLOHMANN_JSON_FROM(v1) nlohmann_json_j.at(#v1).get_to(nlohmann_json_t.v1);
+#define NLOHMANN_JSON_FROM_WITH_DEFAULT(v1) nlohmann_json_t.v1 = nlohmann_json_j.value(#v1, nlohmann_json_default_obj.v1);
 
 /*!
 @brief macro
@@ -2641,6 +2642,10 @@ using is_detected_convertible =
  friend void to_json(nlohmann::json& nlohmann_json_j, const Type& nlohmann_json_t) { NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_PASTE(NLOHMANN_JSON_TO, __VA_ARGS__)) } \
  friend void from_json(const nlohmann::json& nlohmann_json_j, Type& nlohmann_json_t) { NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_PASTE(NLOHMANN_JSON_FROM, __VA_ARGS__)) }
 
+#define NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_DEFAULT(Type, ...) \
+ friend void to_json(nlohmann::json& nlohmann_json_j, const Type& nlohmann_json_t) { NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_PASTE(NLOHMANN_JSON_TO, __VA_ARGS__)) } \
+ friend void from_json(const nlohmann::json& nlohmann_json_j, Type& nlohmann_json_t) { Type nlohmann_json_default_obj; NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_PASTE(NLOHMANN_JSON_FROM_WITH_DEFAULT, __VA_ARGS__)) }
+
 /*!
 @brief macro
 @def NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE
@@ -2650,6 +2655,10 @@ using is_detected_convertible =
  inline void to_json(nlohmann::json& nlohmann_json_j, const Type& nlohmann_json_t) { NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_PASTE(NLOHMANN_JSON_TO, __VA_ARGS__)) } \
  inline void from_json(const nlohmann::json& nlohmann_json_j, Type& nlohmann_json_t) { NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_PASTE(NLOHMANN_JSON_FROM, __VA_ARGS__)) }
 
+#define NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_WITH_DEFAULT(Type, ...) \
+ inline void to_json(nlohmann::json& nlohmann_json_j, const Type& nlohmann_json_t) { NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_PASTE(NLOHMANN_JSON_TO, __VA_ARGS__)) } \
+ inline void from_json(const nlohmann::json& nlohmann_json_j, Type& nlohmann_json_t) { Type nlohmann_json_default_obj; NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_PASTE(NLOHMANN_JSON_FROM_WITH_DEFAULT, __VA_ARGS__)) }
+
 
 // inspired from https://stackoverflow.com/a/26745591
 // allows to call any std function as if (e.g. with begin):

test/src/unit-udt_macro.cpp

@@ -59,6 +59,42 @@ class person_with_private_data
  NLOHMANN_DEFINE_TYPE_INTRUSIVE(person_with_private_data, age, name, metadata)
 };
 
+class person_with_private_data_2
+{
+ private:
+ std::string name{};
+ int age = 0;
+ json metadata = nullptr;
+
+ public:
+ bool operator==(const person_with_private_data_2& rhs) const
+ {
+ return name == rhs.name && age == rhs.age && metadata == rhs.metadata;
+ }
+
+ person_with_private_data_2() = default;
+ person_with_private_data_2(std::string name_, int age_, json metadata_)
+ : name(std::move(name_))
+ , age(age_)
+ , metadata(std::move(metadata_))
+ {}
+
+ std::string getName() const
+ {
+ return name;
+ }
+ int getAge() const
+ {
+ return age;
+ }
+ json getMetadata() const
+ {
+ return metadata;
+ }
+
+ NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_DEFAULT(person_with_private_data_2, age, name, metadata)
+};
+
 class person_without_private_data_1
 {
  public:
@@ -103,6 +139,41 @@ class person_without_private_data_2
 
 NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE(person_without_private_data_2, age, name, metadata)
 
+class person_without_private_data_3
+{
+ public:
+ std::string name{};
+ int age = 0;
+ json metadata = nullptr;
+
+ bool operator==(const person_without_private_data_3& rhs) const
+ {
+ return name == rhs.name && age == rhs.age && metadata == rhs.metadata;
+ }
+
+ person_without_private_data_3() = default;
+ person_without_private_data_3(std::string name_, int age_, json metadata_)
+ : name(std::move(name_))
+ , age(age_)
+ , metadata(std::move(metadata_))
+ {}
+
+ std::string getName() const
+ {
+ return name;
+ }
+ int getAge() const
+ {
+ return age;
+ }
+ json getMetadata() const
+ {
+ return metadata;
+ }
+};
+
+NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_WITH_DEFAULT(person_without_private_data_3, age, name, metadata)
+
 class person_with_private_alphabet
 {
  public:
@@ -231,7 +302,7 @@ NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE(person_with_public_alphabet, a, b, c, d, e, f
 
 } // namespace persons
 
-TEST_CASE_TEMPLATE("Serialization/deserialization via NLOHMANN_DEFINE_TYPE_INTRUSIVE", T,
+TEST_CASE_TEMPLATE("Serialization/deserialization via NLOHMANN_DEFINE_TYPE_INTRUSIVE and NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE", T,
  persons::person_with_private_data,
  persons::person_without_private_data_1,
  persons::person_without_private_data_2)
@@ -257,6 +328,40 @@ TEST_CASE_TEMPLATE("Serialization/deserialization via NLOHMANN_DEFINE_TYPE_INTRU
  }
 }
 
+TEST_CASE_TEMPLATE("Serialization/deserialization via NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_DEFAULT and NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_WITH_DEFAULT", T,
+ persons::person_with_private_data_2,
+ persons::person_without_private_data_3)
+{
+ SECTION("person with default values")
+ {
+ // serialization of default constructed object
+ T p0;
+ CHECK(json(p0).dump() == "{\"age\":0,\"metadata\":null,\"name\":\"\"}");
+
+ // serialization
+ T p1("Erik", 1, {{"haircuts", 2}});
+ CHECK(json(p1).dump() == "{\"age\":1,\"metadata\":{\"haircuts\":2},\"name\":\"Erik\"}");
+
+ // deserialization
+ auto p2 = json(p1).get<T>();
+ CHECK(p2 == p1);
+
+ // roundtrip
+ CHECK(T(json(p1)) == p1);
+ CHECK(json(T(json(p1))) == json(p1));
+
+ // check default value in case of missing field
+ json j = json(p1);
+ j.erase("name");
+ j.erase("age");
+ j.erase("metadata");
+ T p3 = j.get<T>();
+ CHECK(p3.getName() == "");
+ CHECK(p3.getAge() == 0);
+ CHECK(p3.getMetadata() == nullptr);
+ }
+}
+
 TEST_CASE_TEMPLATE("Serialization/deserialization of classes with 26 public/private member variables via NLOHMANN_DEFINE_TYPE_INTRUSIVE and NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE", T,
  persons::person_with_private_alphabet,
  persons::person_with_public_alphabet)