1 files changed, 29 insertions, 11 deletions
diff --git a/lua/nvim_lsp/util.lua b/lua/nvim_lsp/util.lua
index 33eff0c9..1c68e1fc 100644
--- a/lua/nvim_lsp/util.lua
+++ b/lua/nvim_lsp/util.lua
@@ -46,20 +46,38 @@ function M.add_hook_after(func, new_fn)
   end
 end
 
-function M.tbl_deep_extend(dst, ...)
-  validate { dst = { dst, 't' } }
-  for i = 1, select("#", ...) do
-    local t = select(i, ...)
-    validate { arg = { t, 't' } }
-    for k, v in pairs(t) do
-      if type(v) == 'table' and not vim.tbl_islist(v) then
-        dst[k] = M.tbl_deep_extend(dst[k] or vim.empty_dict(), v)
-      else
-        dst[k] = v
+function M.tbl_deep_extend(behavior, ...)
+  if (behavior ~= 'error' and behavior ~= 'keep' and behavior ~= 'force') then
+    error('invalid "behavior": '..tostring(behavior))
+  end
+
+  if select('#', ...) < 2 then
+    error('wrong number of arguments (given '..tostring(1 + select('#', ...))..', expected at least 3)')
+  end
+
+  local ret = {}
+  if vim._empty_dict_mt ~= nil and getmetatable(select(1, ...)) == vim._empty_dict_mt then
+    ret = vim.empty_dict()
+  end
+
+  for i = 1, select('#', ...) do
+    local tbl = select(i, ...)
+    vim.validate{["after the second argument"] = {tbl,'t'}}
+    if tbl then
+      for k, v in pairs(tbl) do
+        if type(v) == 'table' and not vim.tbl_islist(v) then
+          ret[k] = M.tbl_deep_extend(behavior, ret[k] or vim.empty_dict(), v)
+        elseif behavior ~= 'force' and ret[k] ~= nil then
+          if behavior == 'error' then
+            error('key found in more than one map: '..k)
+          end  -- Else behavior is "keep".
+        else
+          ret[k] = v
+        end
       end
     end
   end
-  return dst
+  return ret
 end
 
 function M.nvim_multiline_command(command)