api: Allow kObjectTypeNil to be zero without breaking compatibility

1 files changed, 23 insertions, 3 deletions

diff --git a/src/nvim/msgpack_rpc/helpers.c b/src/nvim/msgpack_rpc/helpers.c
index 64a018f5c3..972d5b3441 100644
--- a/src/nvim/msgpack_rpc/helpers.c
+++ b/src/nvim/msgpack_rpc/helpers.c
@@ -20,13 +20,20 @@
 static msgpack_zone zone;
 static msgpack_sbuffer sbuffer;
 
+/// Value by which objects represented as EXT type are shifted
+///
+/// Subtracted when packing, added when unpacking. Used to allow moving
+/// buffer/window/tabpage block inside ObjectType enum. This block yet cannot be
+/// split or reordered.
+#define EXT_OBJECT_TYPE_SHIFT kObjectTypeBuffer
+
 #define HANDLE_TYPE_CONVERSION_IMPL(t, lt) \
   bool msgpack_rpc_to_##lt(const msgpack_object *const obj, \
                            Integer *const arg) \
     FUNC_ATTR_NONNULL_ALL \
   { \
     if (obj->type != MSGPACK_OBJECT_EXT \
-        || obj->via.ext.type != kObjectType##t) { \
+        || obj->via.ext.type + EXT_OBJECT_TYPE_SHIFT != kObjectType##t) { \
       return false; \
     } \
     \
@@ -51,7 +58,8 @@ static msgpack_sbuffer sbuffer;
     msgpack_packer pac; \
     msgpack_packer_init(&pac, &sbuffer, msgpack_sbuffer_write); \
     msgpack_pack_int64(&pac, (handle_T)o); \
-    msgpack_pack_ext(res, sbuffer.size, kObjectType##t); \
+    msgpack_pack_ext(res, sbuffer.size, \
+                     kObjectType##t - EXT_OBJECT_TYPE_SHIFT); \
     msgpack_pack_ext_body(res, sbuffer.data, sbuffer.size); \
     msgpack_sbuffer_clear(&sbuffer); \
   }
@@ -211,7 +219,7 @@ bool msgpack_rpc_to_object(const msgpack_object *const obj, Object *const arg)
         break;
       }
       case MSGPACK_OBJECT_EXT: {
-        switch (cur.mobj->via.ext.type) {
+        switch ((ObjectType)(cur.mobj->via.ext.type + EXT_OBJECT_TYPE_SHIFT)) {
           case kObjectTypeBuffer: {
             cur.aobj->type = kObjectTypeBuffer;
             ret = msgpack_rpc_to_buffer(cur.mobj, &cur.aobj->data.integer);
@@ -227,6 +235,15 @@ bool msgpack_rpc_to_object(const msgpack_object *const obj, Object *const arg)
             ret = msgpack_rpc_to_tabpage(cur.mobj, &cur.aobj->data.integer);
             break;
           }
+          case kObjectTypeNil:
+          case kObjectTypeBoolean:
+          case kObjectTypeInteger:
+          case kObjectTypeFloat:
+          case kObjectTypeString:
+          case kObjectTypeArray:
+          case kObjectTypeDictionary: {
+            break;
+          }
         }
         break;
       }
@@ -350,6 +367,9 @@ void msgpack_rpc_from_object(const Object result, msgpack_packer *const res)
   kv_push(stack, ((APIToMPObjectStackItem) { &result, false, 0 }));
   while (kv_size(stack)) {
     APIToMPObjectStackItem cur = kv_last(stack);
+    STATIC_ASSERT(kObjectTypeWindow == kObjectTypeBuffer + 1
+                  && kObjectTypeTabpage == kObjectTypeWindow + 1,
+                  "Buffer, window and tabpage enum items are in order");
     switch (cur.aobj->type) {
       case kObjectTypeNil: {
         msgpack_pack_nil(res);