CXX-2077 Sync allowDiskUse test

data/crud/test_files.txt

@@ -37,4 +37,5 @@ v2/aggregate-merge.json
 v2/aggregate-out-readConcern.json
 v2/bulkWrite-arrayFilters.json
 v2/db-aggregate.json
+v2/find-allowdiskuse.json
 v2/updateWithPipelines.json

src/mongocxx/test/spec/operation.cpp

@@ -267,6 +267,10 @@ document::value operation_runner::_run_find(document::view operation) {
         options.sort(arguments["sort"].get_document().value);
     }
 
+    if (arguments["allowDiskUse"]) {
+        options.allow_disk_use(arguments["allowDiskUse"].get_bool().value);
+    }
+
     if (arguments["modifiers"]) {
         document::view modifiers = arguments["modifiers"].get_document().value;
         if (modifiers["$comment"]) {

src/mongocxx/test_util/client_helpers.cpp

@@ -343,7 +343,7 @@ bool matches(types::bson_value::view main,
                 continue;
             }
             if (main_view.find(el.key()) == main_view.end()) {
-                return false;
+                return el.get_value().type() == type::k_null;
             }
             if (!matches(main_view[el.key()].get_value(), el.get_value(), visitor_fn)) {
                 return false;