Extend list_extend to take start/finish.

runtime/lua/vim/lsp/default_callbacks.lua

@@ -5,12 +5,17 @@ local api = vim.api
 
 local M = {}
 
+local function err_message(...)
+  api.nvim_err_writeln(table.concat(vim.tbl_flatten{...}))
+  api.nvim_command("redraw")
+end
+
 M['textDocument/publishDiagnostics'] = function(_, _, result)
   if not result then return end
   local uri = result.uri
   local bufnr = vim.uri_to_bufnr(uri)
   if not bufnr then
-    api.nvim_err_writeln(string.format("LSP.publishDiagnostics: Couldn't find buffer for %s", uri))
+    err_message("LSP.publishDiagnostics: Couldn't find buffer for ", uri)
     return
   end
   util.buf_clear_diagnostics(bufnr)
@@ -20,11 +25,6 @@ M['textDocument/publishDiagnostics'] = function(_, _, result)
   -- util.buf_loclist(bufnr, result.diagnostics)
 end
 
-local function err_message(...)
-  api.nvim_err_writeln(table.concat(vim.tbl_flatten{...}))
-  api.nvim_command("redraw")
-end
-
 local function log_message(_, _, result, client_id)
   local message_type = result.type
   local message = result.message
@@ -34,8 +34,6 @@ local function log_message(_, _, result, client_id)
     err_message("LSP[", client_name, "] client has shut down after sending the message")
   end
   if message_type == protocol.MessageType.Error then
-    -- Might want to not use err_writeln,
-    -- but displaying a message with red highlights or something
     err_message("LSP[", client_name, "] ", message)
   else
     local message_type_name = protocol.MessageType[message_type]

runtime/lua/vim/lsp/util.lua

@@ -546,7 +546,6 @@ end
 
 -- Remove empty lines from the beginning and end.
 function M.trim_empty_lines(lines)
-  local result = {}
   local start = 1
   for i = 1, #lines do
     if #lines[i] > 0 then
@@ -561,11 +560,7 @@ function M.trim_empty_lines(lines)
       break
     end
   end
-  -- TODO(ashkan) use tbl_slice.
-  for i = start, finish do
-    table.insert(result, lines[i])
-  end
-  return result
+  return vim.list_extend({}, lines, start, finish)
 end
 
 -- Accepts markdown lines and tries to reduce it to a filetype if it is

runtime/lua/vim/shared.lua

@@ -226,18 +226,25 @@ function vim.tbl_add_reverse_lookup(o)
   return o
 end
 
---- Extends a list-like table with the values of another list-like table.
----
+-- Extends a list-like table with the values of another list-like table.
+--
 -- NOTE: This *mutates* dst!
 -- @see |extend()|
----
---@param dst The list which will be modified and appended to.
---@param src The list from which values will be inserted.
-function vim.list_extend(dst, src)
-  assert(type(dst) == 'table', "dst must be a table")
-  assert(type(src) == 'table', "src must be a table")
-  for _, v in ipairs(src) do
-    table.insert(dst, v)
+--
+-- @param dst list which will be modified and appended to.
+-- @param src list from which values will be inserted.
+-- @param start Start index on src. defaults to 1
+-- @param finish Final index on src. defaults to #src
+-- @returns dst
+function vim.list_extend(dst, src, start, finish)
+  vim.validate {
+    dst = {dst, 't'};
+    src = {src, 't'};
+    start = {start, 'n', true};
+    finish = {finish, 'n', true};
+  }
+  for i = start or 1, finish or #src do
+    table.insert(dst, src[i])
   end
   return dst
 end

test/functional/lua/vim_spec.lua

@@ -353,10 +353,14 @@ describe('lua stdlib', function()
 
   it('vim.list_extend', function()
     eq({1,2,3}, exec_lua [[ return vim.list_extend({1}, {2,3}) ]])
-    eq('Error executing lua: .../shared.lua: src must be a table',
+    eq('Error executing lua: .../shared.lua: src: expected table, got nil',
       pcall_err(exec_lua, [[ return vim.list_extend({1}, nil) ]]))
     eq({1,2}, exec_lua [[ return vim.list_extend({1}, {2;a=1}) ]])
     eq(true, exec_lua [[ local a = {1} return vim.list_extend(a, {2;a=1}) == a ]])
+    eq({2}, exec_lua [[ return vim.list_extend({}, {2;a=1}, 1) ]])
+    eq({}, exec_lua [[ return vim.list_extend({}, {2;a=1}, 2) ]])
+    eq({}, exec_lua [[ return vim.list_extend({}, {2;a=1}, 1, -1) ]])
+    eq({2}, exec_lua [[ return vim.list_extend({}, {2;a=1}, -1, 2) ]])
   end)
 
   it('vim.tbl_add_reverse_lookup', function()