From df0f612d1b32f04a191078db75c8f3deb4655cdb Mon Sep 17 00:00:00 2001
From: Julian Becker <becker.julian@gmail.com>
Date: Sun, 7 Oct 2018 20:08:05 +0200
Subject: [PATCH] BSON: allow and discard values and object entries of type
 `value_t::discarded`

---
 .../nlohmann/detail/output/binary_writer.hpp  |  5 +++-
 single_include/nlohmann/json.hpp              |  5 +++-
 test/src/unit-bson.cpp                        | 25 +++++++++++++++++++
 3 files changed, 33 insertions(+), 2 deletions(-)

diff --git a/include/nlohmann/detail/output/binary_writer.hpp b/include/nlohmann/detail/output/binary_writer.hpp
index bce5116d..0ec237ea 100644
--- a/include/nlohmann/detail/output/binary_writer.hpp
+++ b/include/nlohmann/detail/output/binary_writer.hpp
@@ -9,7 +9,6 @@
 #include <nlohmann/detail/input/binary_reader.hpp>
 #include <nlohmann/detail/output/output_adapters.hpp>
 
-
 namespace nlohmann
 {
 namespace detail
@@ -864,6 +863,8 @@ class binary_writer
                 assert(false);
                 return 0ul;
             // LCOV_EXCL_STOP
+            case value_t::discarded:
+                return 0ul;
             case value_t::object:
                 return header_size + calc_bson_object_size(*j.m_value.object);
             case value_t::array:
@@ -898,6 +899,8 @@ class binary_writer
                 assert(false);
                 return;
             // LCOV_EXCL_STOP
+            case value_t::discarded:
+                return;
             case value_t::object:
                 return write_bson_object_entry(name, *j.m_value.object);
             case value_t::array:
diff --git a/single_include/nlohmann/json.hpp b/single_include/nlohmann/json.hpp
index 48b17d17..98c6b1f1 100644
--- a/single_include/nlohmann/json.hpp
+++ b/single_include/nlohmann/json.hpp
@@ -7853,7 +7853,6 @@ class binary_reader
 // #include <nlohmann/detail/output/output_adapters.hpp>
 
 
-
 namespace nlohmann
 {
 namespace detail
@@ -8708,6 +8707,8 @@ class binary_writer
                 assert(false);
                 return 0ul;
             // LCOV_EXCL_STOP
+            case value_t::discarded:
+                return 0ul;
             case value_t::object:
                 return header_size + calc_bson_object_size(*j.m_value.object);
             case value_t::array:
@@ -8742,6 +8743,8 @@ class binary_writer
                 assert(false);
                 return;
             // LCOV_EXCL_STOP
+            case value_t::discarded:
+                return;
             case value_t::object:
                 return write_bson_object_entry(name, *j.m_value.object);
             case value_t::array:
diff --git a/test/src/unit-bson.cpp b/test/src/unit-bson.cpp
index 33ef25c4..4a1b387e 100644
--- a/test/src/unit-bson.cpp
+++ b/test/src/unit-bson.cpp
@@ -376,6 +376,31 @@ TEST_CASE("BSON")
             CHECK(json::from_bson(result, true, false) == j);
         }
 
+        SECTION("discarded values are not serialized")
+        {
+            json j = json::value_t::discarded;
+            const auto result = json::to_bson(j);
+            CHECK(result.empty());
+        }
+
+        SECTION("discarded members are not serialized")
+        {
+            json j =
+            {
+                { "entry", json::value_t::discarded }
+            };
+
+            std::vector<uint8_t> expected =
+            {
+                0x05, 0x00, 0x00, 0x00, // size (little endian)
+                // no entries
+                0x00 // end marker
+            };
+
+            const auto result = json::to_bson(j);
+            CHECK(result == expected);
+        }
+
 
         SECTION("non-empty object with object member")
         {