Mutable v4

json11.cpp

@@ -138,6 +138,7 @@ void Json::dump(string &out) const {
 template <Json::Type tag, typename T>
 class Value : public JsonValue {
 protected:
+    friend class JsonIndex;
 
     // Constructors
     explicit Value(const T &value) : m_value(value) {}
@@ -156,7 +157,7 @@ protected:
         return m_value < static_cast<const Value<tag, T> *>(other)->m_value;
     }
 
-    const T m_value;
+    T m_value;
     void dump(string &out) const override { json11::dump(m_value, out); }
 };
 
@@ -320,14 +321,14 @@ Json::Json(Json::object &&values)      : m_ptr(make_shared<JsonObject>(move(valu
 Json::Type Json::type()                           const { return m_ptr->type();         }
 double Json::number_value()                       const { return m_ptr->number_value(); }
 int64_ Json::int64_value()                        const { return m_ptr->int64_value();  }
-uint64_ Json::uint64_value()                        const { return m_ptr->uint64_value();  }
+uint64_ Json::uint64_value()                      const { return m_ptr->uint64_value();  }
 bool Json::bool_value()                           const { return m_ptr->bool_value();   }
 string Json::as_string()                          const { return m_ptr->as_string(); }
 const string & Json::string_value()               const { return m_ptr->string_value(); }
 const vector<Json> & Json::array_items()          const { return m_ptr->array_items();  }
 const map<string, Json> & Json::object_items()    const { return m_ptr->object_items(); }
 const Json & Json::operator[] (size_t i)          const { return (*m_ptr)[i];           }
-const Json & Json::operator[] (const string &key) const { return (*m_ptr)[key];         }
+JsonIndex Json::operator[] (const string &key)          { return (JsonIndex){ .m_object = *this, .m_key = key }; }
 
 double                    JsonValue::number_value()              const { return 0; }
 int64_                    JsonValue::int64_value()               const { return 0; }
@@ -769,8 +770,6 @@ struct JsonParser final {
                     return fail("expected ',' in object, got " + esc(ch));
 
                 ch = get_next_token();
-                if (ch == '}')
-                    break;
             }
             return data;
         }
@@ -794,8 +793,6 @@ struct JsonParser final {
                     return fail("expected ',' in list, got " + esc(ch));
 
                 ch = get_next_token();
-                if (ch == ']')
-                    break;
                 (void)ch;
             }
             return data;
@@ -846,8 +843,13 @@ bool Json::has_shape(const shape & types, string & err) const {
         return false;
     }
 
+    const auto & obj = object_items();
     for (auto & item : types) {
-        if ((*this)[item.first].type() != item.second) {
+        auto it = obj.find(item.first);
+        if (it == obj.end()) {
+            return false;
+        }
+        if (it->second.type() != item.second) {
             err = "bad type for " + item.first + " in " + dump();
             return false;
         }
@@ -856,4 +858,22 @@ bool Json::has_shape(const shape & types, string & err) const {
     return true;
 }
 
+/* * * * * * * * * * * * * * * * * * * *
+ * Indexed wrapper to prevent autovivification
+ */
+
+const Json & JsonIndex::self() const {
+    if (m_object.is_object()) {
+        return ((JsonObject*)m_object.m_ptr.get())->m_value[m_key];
+    }
+    return static_null();
+}
+
+Json JsonIndex::operator =(Json value) {
+    if (m_object.is_object()) {
+        return ((JsonObject*)m_object.m_ptr.get())->m_value[m_key] = value;
+    }
+    return value;
+}
+
 } // namespace json11

json11.hpp

@@ -77,6 +77,8 @@ enum JsonParse {
 
 class JsonValue;
 
+class JsonIndex;
+
 #if __cplusplus < 201103L
     #error This project can only be compiled with a compiler that supports C++11
 #else
@@ -165,7 +167,7 @@ public:
     // Return a reference to arr[i] if this is an array, Json() otherwise.
     const Json & operator[](size_t i) const;
     // Return a reference to obj[key] if this is an object, Json() otherwise.
-    const Json & operator[](const std::string &key) const;
+    JsonIndex operator[](const std::string &key);
 
     // Serialize.
     void dump(std::string &out) const;
@@ -220,9 +222,38 @@ public:
     bool has_shape(const shape & types, std::string & err) const;
 
 private:
+    friend class JsonIndex;
     std::shared_ptr<JsonValue> m_ptr;
 };
 
+class JsonIndex {
+public:
+    Json m_object;
+    const std::string & m_key;
+
+    Json operator =(Json value);
+    operator const Json &() { return m_object[m_key]; }
+    const Json & self() const;
+
+    bool is_null()   const { return self().is_null(); }
+    bool is_number() const { return self().is_number(); }
+    bool is_bool()   const { return self().is_bool(); }
+    bool is_string() const { return self().is_string(); }
+    bool is_array()  const { return self().is_array(); }
+    bool is_object() const { return self().is_object(); }
+
+    double number_value() const { return self().number_value(); }
+    int64_ int64_value() const { return self().int64_value(); }
+    uint64_ uint64_value() const { return self().uint64_value(); }
+    std::string as_string() const { return self().as_string(); }
+    bool bool_value() const { return self().bool_value(); }
+    const std::string &string_value() const { return self().string_value(); }
+    const Json::array &array_items() const { return self().array_items(); }
+    const Json::object &object_items() const { return self().object_items(); }
+
+    std::string dump() const { return self().dump(); }
+};
+
 // Internal class hierarchy - JsonValue objects are not exposed to users of this API.
 class JsonValue {
 protected: