vim-patch:8.2.4858: K_SPECIAL may be escaped twice

Problem:    K_SPECIAL may be escaped twice.
Solution:   Avoid double escaping. (closes vim/vim#10340)
https://github.com/vim/vim/commit/db08887f24d20be11d184ce321bc0890613e42bd

4 files changed, 50 insertions, 2 deletions

diff --git a/src/nvim/testdir/test_eval_stuff.vim b/src/nvim/testdir/test_eval_stuff.vim
index 95eccde35c..811c6c946d 100644
--- a/src/nvim/testdir/test_eval_stuff.vim
+++ b/src/nvim/testdir/test_eval_stuff.vim
@@ -320,4 +320,26 @@ func Test_curly_assignment()
   unlet g:gvar
 endfunc
 
+" K_SPECIAL in the modified character used be escaped, which causes
+" double-escaping with feedkeys() or as the return value of an <expr> mapping,
+" and doesn't match what getchar() returns,
+func Test_modified_char_no_escape_special()
+  nnoremap <M-…> <Cmd>let g:got_m_ellipsis += 1<CR>
+  call feedkeys("\<M-…>", 't')
+  call assert_equal("\<M-…>", getchar())
+  let g:got_m_ellipsis = 0
+  call feedkeys("\<M-…>", 'xt')
+  call assert_equal(1, g:got_m_ellipsis)
+  func Func()
+    return "\<M-…>"
+  endfunc
+  nmap <expr> <F2> Func()
+  call feedkeys("\<F2>", 'xt')
+  call assert_equal(2, g:got_m_ellipsis)
+  delfunc Func
+  nunmap <F2>
+  unlet g:got_m_ellipsis
+  nunmap <M-…>
+endfunc
+
 " vim: shiftwidth=2 sts=2 expandtab
diff --git a/src/nvim/testdir/test_feedkeys.vim b/src/nvim/testdir/test_feedkeys.vim
index f343b0174c..fb64711863 100644
--- a/src/nvim/testdir/test_feedkeys.vim
+++ b/src/nvim/testdir/test_feedkeys.vim
@@ -23,4 +23,15 @@ func Test_feedkeys_with_abbreviation()
   iunabbrev trigger
 endfunc
 
+func Test_feedkeys_escape_special()
+  nnoremap … <Cmd>let g:got_ellipsis += 1<CR>
+  call feedkeys('…', 't')
+  call assert_equal('…', getcharstr())
+  let g:got_ellipsis = 0
+  call feedkeys('…', 'xt')
+  call assert_equal(1, g:got_ellipsis)
+  unlet g:got_ellipsis
+  nunmap …
+endfunc
+
 " vim: shiftwidth=2 sts=2 expandtab
diff --git a/src/nvim/testdir/test_functions.vim b/src/nvim/testdir/test_functions.vim
index f8be250f73..87606f17b8 100644
--- a/src/nvim/testdir/test_functions.vim
+++ b/src/nvim/testdir/test_functions.vim
@@ -1751,8 +1751,8 @@ func Test_nr2char()
   call assert_equal('a', nr2char(97, 1))
   call assert_equal('a', nr2char(97, 0))
 
-  call assert_equal("\x80\xfc\b\xf4\x80\xfeX\x80\xfeX\x80\xfeX", eval('"\<M-' .. nr2char(0x100000) .. '>"'))
-  call assert_equal("\x80\xfc\b\xfd\x80\xfeX\x80\xfeX\x80\xfeX\x80\xfeX\x80\xfeX", eval('"\<M-' .. nr2char(0x40000000) .. '>"'))
+  call assert_equal("\x80\xfc\b" .. nr2char(0x100000), eval('"\<M-' .. nr2char(0x100000) .. '>"'))
+  call assert_equal("\x80\xfc\b" .. nr2char(0x40000000), eval('"\<M-' .. nr2char(0x40000000) .. '>"'))
 endfunc
 
 " Test for getcurpos() and setpos()
diff --git a/src/nvim/testdir/test_mapping.vim b/src/nvim/testdir/test_mapping.vim
index 1da3b71a32..752b1700d0 100644
--- a/src/nvim/testdir/test_mapping.vim
+++ b/src/nvim/testdir/test_mapping.vim
@@ -1025,4 +1025,19 @@ func Test_unmap_simplifiable()
   unmap <C-I>
 endfunc
 
+func Test_expr_map_escape_special()
+  nnoremap … <Cmd>let g:got_ellipsis += 1<CR>
+  func Func()
+    return '…'
+  endfunc
+  nmap <expr> <F2> Func()
+  let g:got_ellipsis = 0
+  call feedkeys("\<F2>", 'xt')
+  call assert_equal(1, g:got_ellipsis)
+  delfunc Func
+  nunmap <F2>
+  unlet g:got_ellipsis
+  nunmap …
+endfunc
+
 " vim: shiftwidth=2 sts=2 expandtab