vim-patch:8.2.5043: can open a cmdline window from a substitute expression

Problem:    Can open a cmdline window from a substitute expression.
Solution:   Disallow opening a command line window when text or buffer is
            locked.
https://github.com/vim/vim/commit/71223e2db87c2bf3b09aecb46266b56cda26191d

4 files changed, 45 insertions, 10 deletions

diff --git a/src/nvim/buffer.c b/src/nvim/buffer.c
index 411705cfa3..7e1eae9632 100644
--- a/src/nvim/buffer.c
+++ b/src/nvim/buffer.c
@@ -1963,11 +1963,7 @@ int buflist_getfile(int n, linenr_T lnum, int options, int forceit)
     return OK;
   }
 
-  if (text_locked()) {
-    text_locked_msg();
-    return FAIL;
-  }
-  if (curbuf_locked()) {
+  if (text_or_buf_locked()) {
     return FAIL;
   }
 
diff --git a/src/nvim/ex_getln.c b/src/nvim/ex_getln.c
index f322c46bf1..51085c4fa0 100644
--- a/src/nvim/ex_getln.c
+++ b/src/nvim/ex_getln.c
@@ -2726,6 +2726,17 @@ char *get_text_locked_msg(void)
   }
 }
 
+/// Check for text, window or buffer locked.
+/// Give an error message and return true if something is locked.
+bool text_or_buf_locked(void)
+{
+  if (text_locked()) {
+    text_locked_msg();
+    return true;
+  }
+  return curbuf_locked();
+}
+
 /// Check if "curbuf->b_ro_locked" or "allbuf_lock" is set and
 /// return true when it is and give an error message.
 bool curbuf_locked(void)
@@ -6600,6 +6611,11 @@ static int open_cmdwin(void)
   bool save_exmode = exmode_active;
   int save_cmdmsg_rl = cmdmsg_rl;
 
+  // Can't do this when text or buffer is locked.
+  if (text_or_buf_locked()) {
+    return K_IGNORE;
+  }
+
   // Can't do this recursively.  Can't do it when typing a password.
   if (cmdwin_type != 0
       || cmdline_star > 0) {
diff --git a/src/nvim/testdir/test_substitute.vim b/src/nvim/testdir/test_substitute.vim
index e06da3b44f..bc1b3fae4b 100644
--- a/src/nvim/testdir/test_substitute.vim
+++ b/src/nvim/testdir/test_substitute.vim
@@ -1,5 +1,7 @@
 " Tests for the substitute (:s) command
 
+source shared.vim
+
 func Test_multiline_subst()
   enew!
   call append(0, ["1 aa",
@@ -873,6 +875,31 @@ func Test_sub_undo_change()
   delfunc Repl
 endfunc
 
+" This was opening a command line window from the expression
+func Test_sub_open_cmdline_win()
+  " the error only happens in a very specific setup, run a new Vim instance to
+  " get a clean starting point.
+  let lines =<< trim [SCRIPT]
+    norm o0000000000000000000000000000000000000000000000000000
+    func Replace()
+      norm q/
+    endfunc
+    s/\%')/\=Replace()
+    redir >Xresult
+    messages
+    redir END
+    qall!
+  [SCRIPT]
+  call writefile(lines, 'Xscript')
+  if RunVim([], [], '-u NONE -S Xscript')
+    let messages = readfile('Xresult')
+    call assert_match('E565: Not allowed to change text or change window', messages[3])
+  endif
+
+  call delete('Xscript')
+  call delete('Xresult')
+endfunc
+
 " Test for the 2-letter and 3-letter :substitute commands
 func Test_substitute_short_cmd()
   new
diff --git a/src/nvim/window.c b/src/nvim/window.c
index ee0d19b1fe..771a85479d 100644
--- a/src/nvim/window.c
+++ b/src/nvim/window.c
@@ -4571,12 +4571,8 @@ void win_goto(win_T *wp)
 {
   win_T *owp = curwin;
 
-  if (text_locked()) {
+  if (text_or_buf_locked()) {
     beep_flush();
-    text_locked_msg();
-    return;
-  }
-  if (curbuf_locked()) {
     return;
   }