vim-patch:9.0.0511: unnecessary scrolling for message of only one line (#20261)

Problem:    Unnecessary scrolling for message of only one line.
Solution:   Only set msg_scroll when needed. (closes vim/vim#11178)
https://github.com/vim/vim/commit/bdedd2bcce3a59028c7504a397ff77d901b1b12a

1 files changed, 32 insertions, 0 deletions

diff --git a/src/nvim/testdir/test_messages.vim b/src/nvim/testdir/test_messages.vim
index a83fcd7138..0f348c22cb 100644
--- a/src/nvim/testdir/test_messages.vim
+++ b/src/nvim/testdir/test_messages.vim
@@ -171,6 +171,38 @@ func Test_echospace()
   set ruler& showcmd&
 endfunc
 
+func Test_warning_scroll()
+  CheckRunVimInTerminal
+  let lines =<< trim END
+      call test_override('ui_delay', 50)
+      set noruler
+      set readonly
+      undo
+  END
+  call writefile(lines, 'XTestWarningScroll', 'D')
+  let buf = RunVimInTerminal('', #{rows: 8})
+
+  " When the warning comes from a script, messages are scrolled so that the
+  " stacktrace is visible.
+  call term_sendkeys(buf, ":source XTestWarningScroll\n")
+  " only match the final colon in the line that shows the source
+  call WaitForAssert({-> assert_match(':$', term_getline(buf, 5))})
+  call WaitForAssert({-> assert_equal('line    4:W10: Warning: Changing a readonly file', term_getline(buf, 6))})
+  call WaitForAssert({-> assert_equal('Already at oldest change', term_getline(buf, 7))})
+  call WaitForAssert({-> assert_equal('Press ENTER or type command to continue', term_getline(buf, 8))})
+  call term_sendkeys(buf, "\n")
+
+  " When the warning does not come from a script, messages are not scrolled.
+  call term_sendkeys(buf, ":enew\n")
+  call term_sendkeys(buf, ":set readonly\n")
+  call term_sendkeys(buf, 'u')
+  call WaitForAssert({-> assert_equal('W10: Warning: Changing a readonly file', term_getline(buf, 8))})
+  call WaitForAssert({-> assert_equal('Already at oldest change', term_getline(buf, 8))})
+
+  " clean up
+  call StopVimInTerminal(buf)
+endfunc
+
 " Test more-prompt (see :help more-prompt).
 func Test_message_more()
   CheckRunVimInTerminal