CXX-2143 throw an exception when getting types from an unset element

Author: samantharitter

src/bsoncxx/document/element.cpp

@@ -79,10 +79,14 @@ stdx::string_view element::key() const {
     return stdx::string_view{key};
 }
 
-#define BSONCXX_ENUM(name, val)                                     \
-    types::b_##name element::get_##name() const {                   \
-        types::bson_value::view v{_raw, _length, _offset, _keylen}; \
-        return v.get_##name();                                      \
+#define BSONCXX_ENUM(name, val)                                                             \
+    types::b_##name element::get_##name() const {                                           \
+        if (_raw == nullptr) {                                                              \
+            throw bsoncxx::exception{error_code::k_unset_element,                           \
+                                     "cannot get " #name " from an uninitialized element"}; \
+        }                                                                                   \
+        types::bson_value::view v{_raw, _length, _offset, _keylen};                         \
+        return v.get_##name();                                                              \
     }
 #include <bsoncxx/enums/type.hpp>
 #undef BSONCXX_ENUM

src/bsoncxx/test/bson_types.cpp

@@ -19,6 +19,7 @@
 
 #include <bsoncxx/builder/basic/array.hpp>
 #include <bsoncxx/builder/basic/document.hpp>
+#include <bsoncxx/document/element.hpp>
 #include <bsoncxx/stdx/string_view.hpp>
 #include <bsoncxx/test_util/catch.hh>
 
@@ -28,6 +29,7 @@ using namespace bsoncxx;
 using namespace types;
 using bsoncxx::builder::basic::make_document;
 using bsoncxx::builder::basic::kvp;
+using bsoncxx::document::element;
 
 TEST_CASE("type to_string", "[bsoncxx::type::to_string]") {
     REQUIRE(to_string(bsoncxx::type::k_bool) == "bool");
@@ -186,6 +188,15 @@ TEST_CASE("b_maxkey", "[bsoncxx::type::b_maxkey]") {
     REQUIRE(a == a);
 }
 
+TEST_CASE("getting types from an uninitialized element throws", "[bsoncxx::document::element]") {
+    element elem{};
+    REQUIRE_THROWS(elem.get_value());
+
+#define BSONCXX_ENUM(name, val) REQUIRE_THROWS(elem.get_##name());
+#include <bsoncxx/enums/type.hpp>
+#undef BSONCXX_ENUM
+}
+
 TEST_CASE("bson_value::view returns correct type", "[bsoncxx::types::bson_value::view]") {
     b_bool bool_val{true};
     REQUIRE(bson_value::view{bool_val}.type() == bsoncxx::type::k_bool);