executor/converter: Make it possible to supply {} to Dictionary arg

src/nvim/viml/executor/converter.c

@@ -33,6 +33,7 @@ typedef struct {
                     ///< either kObjectTypeNil, kObjectTypeDictionary or
                     ///< kObjectTypeArray, depending on other properties.
   lua_Number val;  ///< If has_val_key and val_type == LUA_TNUMBER: value.
+  bool has_type_key;  ///< True if type key is present.
 } LuaTableProps;
 
 #ifdef INCLUDE_GENERATED_DECLARATIONS
@@ -48,8 +49,6 @@ typedef struct {
 static LuaTableProps nlua_traverse_table(lua_State *const lstate)
   FUNC_ATTR_NONNULL_ALL FUNC_ATTR_WARN_UNUSED_RESULT
 {
-  bool has_type_key = false;  // True if type key was found,
-                              // @see nlua_push_type_idx().
   size_t tsize = 0;  // Total number of keys.
   int val_type = 0;  // If has_val_key: lua type of the value.
   bool has_val_key = false;  // True if val key was found,
@@ -96,7 +95,7 @@ static LuaTableProps nlua_traverse_table(lua_State *const lstate)
             if (n == (lua_Number)kObjectTypeFloat
                 || n == (lua_Number)kObjectTypeArray
                 || n == (lua_Number)kObjectTypeDictionary) {
-              has_type_key = true;
+              ret.has_type_key = true;
               ret.type = (ObjectType)n;
             } else {
               other_keys_num++;
@@ -121,7 +120,7 @@ static LuaTableProps nlua_traverse_table(lua_State *const lstate)
     tsize++;
     lua_pop(lstate, 1);
   }
-  if (has_type_key) {
+  if (ret.has_type_key) {
     if (ret.type == kObjectTypeFloat
         && (!has_val_key || val_type != LUA_TNUMBER)) {
       ret.type = kObjectTypeNil;
@@ -133,7 +132,7 @@ static LuaTableProps nlua_traverse_table(lua_State *const lstate)
       // should be ignored.
       if (ret.maxidx != 0
           && ret.maxidx != (tsize
-                            - has_type_key
+                            - ret.has_type_key
                             - other_keys_num
                             - has_val_key
                             - ret.string_keys_num)) {
@@ -789,7 +788,12 @@ static inline LuaTableProps nlua_check_type(lua_State *const lstate,
     }
     return (LuaTableProps) { .type = kObjectTypeNil };
   }
-  const LuaTableProps table_props = nlua_traverse_table(lstate);
+  LuaTableProps table_props = nlua_traverse_table(lstate);
+
+  if (type == kObjectTypeDictionary && table_props.type == kObjectTypeArray
+      && table_props.maxidx == 0 && !table_props.has_type_key) {
+    table_props.type = kObjectTypeDictionary;
+  }
 
   if (table_props.type != type) {
     if (err) {

test/functional/lua_spec.lua

@@ -234,11 +234,29 @@ describe('luaeval() function', function()
 
     eq({}, funcs.luaeval('vim.api._vim_id_array({[vim.type_idx]=vim.types.array})'))
 
-    -- Presence of type_idx makes Vim ignore some keys
     eq({42}, funcs.luaeval('vim.api._vim_id_array({[vim.type_idx]=vim.types.array, [vim.val_idx]=10, [5]=1, foo=2, [1]=42})'))
     eq({{foo=2}}, funcs.luaeval('vim.api._vim_id_array({{[vim.type_idx]=vim.types.dictionary, [vim.val_idx]=10, [5]=1, foo=2, [1]=42}})'))
     eq({10}, funcs.luaeval('vim.api._vim_id_array({{[vim.type_idx]=vim.types.float, [vim.val_idx]=10, [5]=1, foo=2, [1]=42}})'))
     eq({}, funcs.luaeval('vim.api._vim_id_array({[vim.type_idx]=vim.types.array, [vim.val_idx]=10, [5]=1, foo=2})'))
+
+    eq({}, funcs.luaeval('vim.api._vim_id_array({})'))
+    eq(3, eval([[type(luaeval('vim.api._vim_id_array({})'))]]))
+  end)
+
+  it('correctly converts dictionaries with type_idx to API objects', function()
+    eq(4, eval([[type(luaeval('vim.api._vim_id_dictionary({[vim.type_idx]=vim.types.dictionary})'))]]))
+
+    eq({}, funcs.luaeval('vim.api._vim_id_dictionary({[vim.type_idx]=vim.types.dictionary})'))
+
+    eq({v={42}}, funcs.luaeval('vim.api._vim_id_dictionary({v={[vim.type_idx]=vim.types.array, [vim.val_idx]=10, [5]=1, foo=2, [1]=42}})'))
+    eq({foo=2}, funcs.luaeval('vim.api._vim_id_dictionary({[vim.type_idx]=vim.types.dictionary, [vim.val_idx]=10, [5]=1, foo=2, [1]=42})'))
+    eq({v=10}, funcs.luaeval('vim.api._vim_id_dictionary({v={[vim.type_idx]=vim.types.float, [vim.val_idx]=10, [5]=1, foo=2, [1]=42}})'))
+    eq({v={}}, funcs.luaeval('vim.api._vim_id_dictionary({v={[vim.type_idx]=vim.types.array, [vim.val_idx]=10, [5]=1, foo=2}})'))
+
+    -- If API requests dictionary, then empty table will be the one. This is not
+    -- the case normally because empty table is an empty arrray.
+    eq({}, funcs.luaeval('vim.api._vim_id_dictionary({})'))
+    eq(4, eval([[type(luaeval('vim.api._vim_id_dictionary({})'))]]))
   end)
 
   it('correctly converts self-containing containers', function()