feat(vimscript): log function name in "fast" message #32616

(cherry picked from commit e42050f4ae)

src/nvim/lua/executor.c

@@ -1152,7 +1152,10 @@ int nlua_call(lua_State *lstate)
   size_t name_len;
   const char *name = luaL_checklstring(lstate, 1, &name_len);
   if (!nlua_is_deferred_safe() && !viml_func_is_fast(name)) {
-    return luaL_error(lstate, e_fast_api_disabled, "Vimscript function");
+    size_t length = MIN(strlen(name), 100) + sizeof("Vimscript function \"\"");
+    vim_snprintf(IObuff, length, "Vimscript function \"%s\"", name);
+    int ret = luaL_error(lstate, e_fast_api_disabled, IObuff);
+    return ret;
   }
 
   int nargs = lua_gettop(lstate) - 1;

test/functional/lua/vim_spec.lua

@@ -1328,6 +1328,22 @@ describe('lua stdlib', function()
     )
   end)
 
+  it('vim.call fails in fast context', function()
+    local screen = Screen.new(120, 10)
+    exec_lua([[
+      local timer = vim.uv.new_timer()
+      timer:start(0, 0, function()
+        timer:close()
+        vim.call('sin', 0.0)
+      end)
+    ]])
+    screen:expect({
+      any = pesc('E5560: Vimscript function "sin" must not be called in a fast event context'),
+    })
+    feed('<CR>')
+    assert_alive()
+  end)
+
   it('vim.fn errors when calling API function', function()
     matches(
       'Tried to call API function with vim.fn: use vim.api.nvim_get_current_line instead',