Add support for indenting method chaining

Support indenting chained method calls:

  local colon_out = self.kitchen
    :getContents()
    :getCheese()
    :enjoyCheese(self
      :mouth()
      :open()
      :extendTongue())
    :eatCheese()
    :digestCheese()

  local dot_out = self.kitchen
    .getContents()
    .getCheese()
    .enjoyCheese(self
      .mouth()
      .open()
      .extendTongue())
    .eatCheese()
    .digestCheese()

Author: idbrii

indent/lua.vim

@@ -29,6 +29,8 @@ let s:close_patt = '\C\%(\<\%(end\|until\)\>\|)\|}\)'
 let s:anon_func_start = '\S\+\s*[({].*\<function\s*(.*)\s*$'
 let s:anon_func_end = '\<end\%(\s*[)}]\)\+'
 
+let s:chained_func_call = "^\\v\\s*[:.]\\w+[({\"']"
+
 " Expression used to check whether we should skip a match with searchpair().
 let s:skip_expr = "synIDattr(synID(line('.'),col('.'),1),'name') =~# 'luaComment\\|luaString'"
 
@@ -98,6 +100,16 @@ function GetLuaIndent()
     let i += 1
   endif
 
+  " if the current line chains a function call to previous unchained line
+  if contents_prev !~# s:chained_func_call && contents_cur =~# s:chained_func_call
+    let i += 1
+  endif
+
+  " if the current line chains a function call to previous unchained line
+  if contents_prev =~# s:chained_func_call && contents_cur !~# s:chained_func_call
+    let i -= 1
+  endif
+
   " special case: call(with, {anon = function() -- should indent only once
   if i > 1 && contents_prev =~# s:anon_func_start
     let i = 1