BSON: support objects with null members

include/nlohmann/detail/input/binary_reader.hpp

@@ -203,6 +203,14 @@ class binary_reader
                     sax->boolean(static_cast<bool>(get()));
                 }
                 break;
+                case 0x0A: // null
+                {
+                    string_t key;
+                    get_bson_cstr(key);
+                    sax->key(key);
+                    sax->null();
+                }
+                break;
             }
         }
 

include/nlohmann/detail/output/binary_writer.hpp

@@ -711,6 +711,16 @@ class binary_writer
         return /*id*/ 1ul + name.size() + 1ul + sizeof(std::int32_t) + j.m_value.string->size() + 1ul;
     }
 
+    std::size_t write_bson_null(const typename BasicJsonType::string_t& name, const BasicJsonType&)
+    {
+        oa->write_character(static_cast<CharType>(0x0A)); // null
+        oa->write_characters(
+            reinterpret_cast<const CharType*>(name.c_str()),
+            name.size() + 1u);
+
+        return /*id*/ 1ul + name.size() + 1ul;
+    }
+
     std::size_t write_bson_object_entry(const typename BasicJsonType::string_t& name, const BasicJsonType& j)
     {
         switch (j.type())
@@ -724,6 +734,8 @@ class binary_writer
                 return write_bson_double(name, j);
             case value_t::string:
                 return write_bson_string(name, j);
+            case value_t::null:
+                return write_bson_null(name, j);
         };
 
         return 0ul;

single_include/nlohmann/json.hpp

@@ -6187,6 +6187,14 @@ class binary_reader
                     sax->boolean(static_cast<bool>(get()));
                 }
                 break;
+                case 0x0A: // null
+                {
+                    string_t key;
+                    get_bson_cstr(key);
+                    sax->key(key);
+                    sax->null();
+                }
+                break;
             }
         }
 
@@ -8517,6 +8525,16 @@ class binary_writer
         return /*id*/ 1ul + name.size() + 1ul + sizeof(std::int32_t) + j.m_value.string->size() + 1ul;
     }
 
+    std::size_t write_bson_null(const typename BasicJsonType::string_t& name, const BasicJsonType&)
+    {
+        oa->write_character(static_cast<CharType>(0x0A)); // null
+        oa->write_characters(
+            reinterpret_cast<const CharType*>(name.c_str()),
+            name.size() + 1u);
+
+        return /*id*/ 1ul + name.size() + 1ul;
+    }
+
     std::size_t write_bson_object_entry(const typename BasicJsonType::string_t& name, const BasicJsonType& j)
     {
         switch (j.type())
@@ -8530,6 +8548,8 @@ class binary_writer
                 return write_bson_double(name, j);
             case value_t::string:
                 return write_bson_string(name, j);
+            case value_t::null:
+                return write_bson_null(name, j);
         };
 
         return 0ul;

test/src/unit-bson.cpp

@@ -208,6 +208,29 @@ TEST_CASE("BSON")
             CHECK(json::from_bson(result, true, false) == j);
         }
 
+        SECTION("non-empty object with null member")
+        {
+            json j =
+            {
+                { "entry", nullptr }
+            };
+
+            std::vector<uint8_t> expected =
+            {
+                0x0C, 0x00, 0x00, 0x00, // size (little endian)
+                0x0A, /// entry: null
+                'e', 'n', 't', 'r', 'y', '\x00',
+                0x00 // end marker
+            };
+
+            const auto result = json::to_bson(j);
+            CHECK(result == expected);
+
+            // roundtrip
+            CHECK(json::from_bson(result) == j);
+            CHECK(json::from_bson(result, true, false) == j);
+        }
+
 
     }
 }