test: Refactor functional helpers to use vim_input

The vim_input function accepts raw terminal input and so is better to emulate
real user, especially because it is not deferred as vim_feedkeys.

Using this function required a number of changes:

- expect() was refactored to use curbuf_contents()
- The vim_eval function in request() was moved to curbuf_contents(). For most
  cases this is enough(we only care for synchronizing api calls with user input
  when verifying buffer contents).
- <C-@>(NUL) is preprocessed before being passed to replace_termcodes.
- Legacy test 4 had a bug that only became visible when using vim_input, it is
  fixed now.
- An extra blank line deletion was required for test 101

The last two items show that vim_feedkeys because it is not 100% equivalent to
receiving terminal input.

test/functional/helpers.lua

@@ -42,7 +42,6 @@ local function request(method, ...)
   if not loop_stopped then
     -- Except when the loop has been stopped by a notification triggered
     -- by the initial request, for example.
-    session:request('vim_eval', '1')
   end
   return rv
 end
@@ -99,25 +98,20 @@ local function nvim_eval(expr)
   return request('vim_eval', expr)
 end
 
-local function nvim_feed(input, mode)
-  mode = mode or ''
-  request('vim_feedkeys', input, mode)
-end
-
-local function buffer_slice(start, stop, buffer_idx)
-  local include_end = false
-  if not stop then
-    stop = -1
-    include_end = true
+local function nvim_feed(input)
+  while #input > 0 do
+    local written = request('vim_input', input)
+    input = input:sub(written + 1)
   end
-  local buffer = request('vim_get_buffers')[buffer_idx or 1]
-  local slice = request('buffer_get_line_slice', buffer, start or 0, stop,
-                        true, include_end)
-  return table.concat(slice, '\n')
 end
 
 local function nvim_replace_termcodes(input)
-  return request('vim_replace_termcodes', input, false, true, true)
+  -- small hack to stop <C-@> from being replaced by the internal
+  -- representation(which is different and won't work for vim_input)
+  local temp_replacement = 'CCCCCCCCC@@@@@@@@@@'
+  input = input:gsub('<[Cc][-]@>', temp_replacement)
+  local rv = request('vim_replace_termcodes', input, false, true, true)
+  return rv:gsub(temp_replacement, '\000')
 end
 
 local function dedent(str)
@@ -150,7 +144,7 @@ end
 
 local function rawfeed(...)
   for _, v in ipairs({...}) do
-    nvim_feed(dedent(v), 'nt')
+    nvim_feed(dedent(v))
   end
 end
 
@@ -166,19 +160,19 @@ local function clear()
 end
 
 local function insert(...)
-  nvim_feed('i', 'nt')
+  nvim_feed('i')
   rawfeed(...)
-  nvim_feed(nvim_replace_termcodes('<ESC>'), 'nt')
+  nvim_feed(nvim_replace_termcodes('<ESC>'))
 end
 
 local function execute(...)
   for _, v in ipairs({...}) do
     if v:sub(1, 1) ~= '/' then
       -- not a search command, prefix with colon
-      nvim_feed(':', 'nt')
+      nvim_feed(':')
     end
-    nvim_feed(v, 'nt')
-    nvim_feed(nvim_replace_termcodes('<CR>'), 'nt')
+    nvim_feed(v)
+    nvim_feed(nvim_replace_termcodes('<CR>'))
   end
 end
 
@@ -200,10 +194,6 @@ local function neq(expected, actual)
   return assert.are_not.same(expected, actual)
 end
 
-local function expect(contents, first, last, buffer_index)
-  return eq(dedent(contents), buffer_slice(first, last, buffer_index))
-end
-
 local function ok(expr)
   assert.is_true(expr)
 end
@@ -233,6 +223,10 @@ local function curbuf(method, ...)
 end
 
 local function curbuf_contents()
+  -- Before inspecting the buffer, execute 'vim_eval' to wait until all
+  -- previously sent keys are processed(vim_eval is a deferred function, and
+  -- only processed after all input)
+  session:request('vim_eval', '1')
   return table.concat(curbuf('get_line_slice', 0, -1, true, true), '\n')
 end
 
@@ -252,6 +246,10 @@ local function curtab(method, ...)
   return tabpage(method, tab, ...)
 end
 
+local function expect(contents)
+  return eq(dedent(contents), curbuf_contents())
+end
+
 clear()
 
 return {

test/functional/legacy/004_bufenter_with_modelines_spec.lua

@@ -31,7 +31,7 @@ describe('BufEnter with modelines', function()
     execute('sp Xxx')
 
     -- Append text with autoindent to this file
-    feed('G?this is a<Esc>')
+    feed('G?this is a<CR>')
     feed('othis should be auto-indented<Esc>')
 
     -- Go to Xxx, no autocmd anymore
@@ -39,7 +39,7 @@ describe('BufEnter with modelines', function()
     execute('buf Xxx')
 
     -- Append text without autoindent to Xxx
-    feed('G?this is a<Esc>')
+    feed('G?this is a<CR>')
     feed('othis should be in column 1<Esc>')
     execute('wq')
 

test/functional/legacy/101_hlsearch_spec.lua

@@ -3,6 +3,7 @@
 local helpers = require('test.functional.helpers')
 local clear, feed, insert = helpers.clear, helpers.feed, helpers.insert
 local execute, expect = helpers.execute, helpers.expect
+local eval = helpers.eval
 
 describe('v:hlsearch', function()
   setup(clear)
@@ -44,7 +45,7 @@ describe('v:hlsearch', function()
     execute('$put=r')
     execute('call garbagecollect(1)')
     execute('call getchar()')
-    execute('1d')
+    execute('1d', '1d')
 
     -- Assert buffer contents.
     expect([[

test/functional/shell/viml_system_spec.lua

@@ -10,6 +10,7 @@ local eq, clear, eval, feed, nvim =
 local function create_file_with_nuls(name)
   return function()
     feed('ipart1<C-V>000part2<C-V>000part3<ESC>:w '..name..'<CR>')
+    eval('1')  -- wait for the file to be created
   end
 end