vim-patch:8.2.1844: using "q" at the more prompt doesn't stop a long message

Problem:    Using "q" at the more prompt doesn't stop a long message.
Solution:   Check for "got_int". (closes vim/vim#7122)
3d30af8783

Cherry-pick file name change from patch 8.2.2112.

src/nvim/message.c

@@ -1486,6 +1486,10 @@ int msg_outtrans_len_attr(const char_u *msgstr, int len, int attr)
   char_u *s;
   int mb_l;
   int c;
+  int save_got_int = got_int;
+
+  // Only quit when got_int was set in here.
+  got_int = false;
 
   // if MSG_HIST flag set, add message to history
   if (attr & MSG_HIST) {
@@ -1503,7 +1507,7 @@ int msg_outtrans_len_attr(const char_u *msgstr, int len, int attr)
    * Go over the string.  Special characters are translated and printed.
    * Normal characters are printed several at a time.
    */
-  while (--len >= 0) {
+  while (--len >= 0 && !got_int) {
     // Don't include composing chars after the end.
     mb_l = utfc_ptr2len_len((char_u *)str, len + 1);
     if (mb_l > 1) {
@@ -1542,11 +1546,13 @@ int msg_outtrans_len_attr(const char_u *msgstr, int len, int attr)
     }
   }
 
-  if (str > plain_start) {
+  if (str > plain_start && !got_int) {
     // Print the printable chars at the end.
     msg_puts_attr_len(plain_start, str - plain_start, attr);
   }
 
+  got_int |= save_got_int;
+
   return retval;
 }
 

src/nvim/testdir/test_messages.vim

@@ -2,6 +2,9 @@
 
 source check.vim
 source shared.vim
+source term_util.vim
+source view_util.vim
+source screendump.vim
 
 func Test_messages()
   let oldmore = &more
@@ -109,6 +112,22 @@ func Test_echospace()
   set ruler& showcmd&
 endfunc
 
+func Test_quit_long_message()
+  CheckScreendump
+
+  let content =<< trim END
+    echom range(9999)->join("\x01")
+  END
+  call writefile(content, 'Xtest_quit_message')
+  let buf = RunVimInTerminal('-S Xtest_quit_message', #{rows: 6})
+  call term_sendkeys(buf, "q")
+  call VerifyScreenDump(buf, 'Test_quit_long_message', {})
+
+  " clean up
+  call StopVimInTerminal(buf)
+  call delete('Xtest_quit_message')
+endfunc
+
 " this was missing a terminating NUL
 func Test_echo_string_partial()
   function CountSpaces()

test/functional/legacy/messages_spec.lua

@@ -0,0 +1,38 @@
+local helpers = require('test.functional.helpers')(after_each)
+local Screen = require('test.functional.ui.screen')
+local clear = helpers.clear
+local command = helpers.command
+local feed = helpers.feed
+
+before_each(clear)
+
+describe('messages', function()
+  it('more prompt with control characters can be quit vim-patch:8.2.1844', function()
+    local screen = Screen.new(40, 6)
+    screen:set_default_attr_ids({
+      [1] = {foreground = Screen.colors.Blue},  -- SpecialKey
+      [2] = {bold = true, foreground = Screen.colors.SeaGreen},  -- MoreMsg
+      [3] = {bold = true, foreground = Screen.colors.Blue},  -- NonText
+    })
+    screen:attach()
+    command('set more')
+    feed([[:echom range(9999)->join("\x01")<CR>]])
+    screen:expect([[
+      0{1:^A}1{1:^A}2{1:^A}3{1:^A}4{1:^A}5{1:^A}6{1:^A}7{1:^A}8{1:^A}9{1:^A}10{1:^A}11{1:^A}12|
+      {1:^A}13{1:^A}14{1:^A}15{1:^A}16{1:^A}17{1:^A}18{1:^A}19{1:^A}20{1:^A}21{1:^A}22|
+      {1:^A}23{1:^A}24{1:^A}25{1:^A}26{1:^A}27{1:^A}28{1:^A}29{1:^A}30{1:^A}31{1:^A}32|
+      {1:^A}33{1:^A}34{1:^A}35{1:^A}36{1:^A}37{1:^A}38{1:^A}39{1:^A}40{1:^A}41{1:^A}42|
+      {1:^A}43{1:^A}44{1:^A}45{1:^A}46{1:^A}47{1:^A}48{1:^A}49{1:^A}50{1:^A}51{1:^A}52|
+      {2:-- More --}^                              |
+    ]])
+    feed('q')
+    screen:expect([[
+      ^                                        |
+      {3:~                                       }|
+      {3:~                                       }|
+      {3:~                                       }|
+      {3:~                                       }|
+                                              |
+    ]])
+  end)
+end)