5 files changed, 17 insertions, 8 deletions
diff --git a/src/mongo/db/commands/SConscript b/src/mongo/db/commands/SConscript
index 7f16897f022..908214a6e2f 100644
--- a/src/mongo/db/commands/SConscript
+++ b/src/mongo/db/commands/SConscript
@@ -109,6 +109,7 @@ env.Library(
         '$BUILD_DIR/mongo/db/mongohasher',
         '$BUILD_DIR/mongo/db/server_options_core',
         '$BUILD_DIR/mongo/logger/parse_log_component_settings',
+        '$BUILD_DIR/mongo/rpc/protocol',
     ],
 )
 
diff --git a/src/mongo/db/commands/explain_cmd.cpp b/src/mongo/db/commands/explain_cmd.cpp
index 003047168db..46b0c6eac3f 100644
--- a/src/mongo/db/commands/explain_cmd.cpp
+++ b/src/mongo/db/commands/explain_cmd.cpp
@@ -92,7 +92,7 @@ public:
           _innerRequest{std::move(innerRequest)},
           _innerInvocation{std::move(innerInvocation)} {}
 
-    void run(OperationContext* opCtx, CommandReplyBuilder* result) override {
+    void run(OperationContext* opCtx, rpc::ReplyBuilderInterface* result) override {
         uassert(50746,
                 "Explain's child command cannot run on this node. "
                 "Are you explaining a write command on a secondary?",
diff --git a/src/mongo/db/commands/generic.cpp b/src/mongo/db/commands/generic.cpp
index 277b22aba99..a572b94747c 100644
--- a/src/mongo/db/commands/generic.cpp
+++ b/src/mongo/db/commands/generic.cpp
@@ -108,8 +108,16 @@ public:
             return NamespaceString(request().request.getDatabase());
         }
 
-        void run(OperationContext* opCtx, CommandReplyBuilder* result) override {
-            result->append("echo", request().request.body);
+        void run(OperationContext* opCtx, rpc::ReplyBuilderInterface* result) override {
+            auto sequences = request().request.sequences;
+            for (auto& docSeq : sequences) {
+                auto docBuilder = result->getDocSequenceBuilder(docSeq.name);
+                for (auto& bson : docSeq.objs) {
+                    docBuilder.append(bson);
+                }
+            }
+
+            result->getBodyBuilder().append("echo", request().request.body);
         }
     };
 
diff --git a/src/mongo/db/commands/mr_test.cpp b/src/mongo/db/commands/mr_test.cpp
index f8c81c473a5..6a1f5d67302 100644
--- a/src/mongo/db/commands/mr_test.cpp
+++ b/src/mongo/db/commands/mr_test.cpp
@@ -47,6 +47,7 @@
 #include "mongo/db/repl/replication_coordinator_mock.h"
 #include "mongo/db/repl/storage_interface_impl.h"
 #include "mongo/db/service_context_d_test_fixture.h"
+#include "mongo/rpc/factory.h"
 #include "mongo/rpc/get_status_from_command_result.h"
 #include "mongo/scripting/dbdirectclient_factory.h"
 #include "mongo/scripting/engine.h"
@@ -425,10 +426,9 @@ Status MapReduceCommandTest::_runCommand(StringData mapCode, StringData reduceCo
     ASSERT(command) << "Unable to look up mapReduce command";
 
     auto request = OpMsgRequest::fromDBAndBody(inputNss.db(), _makeCmdObj(mapCode, reduceCode));
-    BufBuilder bb;
-    CommandReplyBuilder crb(BSONObjBuilder{bb});
-    command->parse(_opCtx.get(), request)->run(_opCtx.get(), &crb);
-    auto status = getStatusFromCommandResult(crb.getBodyBuilder().asTempObj());
+    auto replyBuilder = rpc::makeReplyBuilder(rpc::Protocol::kOpMsg);
+    command->parse(_opCtx.get(), request)->run(_opCtx.get(), replyBuilder.get());
+    auto status = getStatusFromCommandResult(replyBuilder->getBodyBuilder().asTempObj());
     if (!status.isOK()) {
         return status.withContext(str::stream() << "mapReduce command failed: " << request.body);
     }
diff --git a/src/mongo/db/commands/write_commands/write_commands.cpp b/src/mongo/db/commands/write_commands/write_commands.cpp
index edbd9a6d315..46ebb7d0e9c 100644
--- a/src/mongo/db/commands/write_commands/write_commands.cpp
+++ b/src/mongo/db/commands/write_commands/write_commands.cpp
@@ -225,7 +225,7 @@ private:
     // Customization point for 'run'.
     virtual void runImpl(OperationContext* opCtx, BSONObjBuilder& result) const = 0;
 
-    void run(OperationContext* opCtx, CommandReplyBuilder* result) final {
+    void run(OperationContext* opCtx, rpc::ReplyBuilderInterface* result) final {
         try {
             try {
                 _transactionChecks(opCtx);