vim-patch:9.1.0046: :drop does not re-use empty buffer (#27165)

Problem:  :drop does not re-use empty buffer
          (Rocco Mao)
Solution: Make :drop re-use an empty buffer
          (Rocco Mao)

fixes: vim/vim#13851
closes: vim/vim#13881

https://github.com/vim/vim/commit/f96dc8d07f752ddd96d1447d85278a85255a1462

Co-authored-by: Rocco Mao <dapeng.mao@qq.com>

2 files changed, 85 insertions, 9 deletions

diff --git a/test/old/testdir/test_excmd.vim b/test/old/testdir/test_excmd.vim
index c729ff4929..b7356c22fa 100644
--- a/test/old/testdir/test_excmd.vim
+++ b/test/old/testdir/test_excmd.vim
@@ -90,23 +90,31 @@ endfunc
 
 " Test for the :drop command
 func Test_drop_cmd()
-  call writefile(['L1', 'L2'], 'Xfile')
+  call writefile(['L1', 'L2'], 'Xdropfile', 'D')
+  " Test for reusing the current buffer
   enew | only
-  drop Xfile
+  let expected_nr = bufnr()
+  drop Xdropfile
+  call assert_equal(expected_nr, bufnr())
   call assert_equal('L2', getline(2))
   " Test for switching to an existing window
   below new
-  drop Xfile
+  drop Xdropfile
   call assert_equal(1, winnr())
-  " Test for splitting the current window
+  " Test for splitting the current window (set nohidden)
   enew | only
   set modified
-  drop Xfile
+  drop Xdropfile
   call assert_equal(2, winnr('$'))
+  " Not splitting the current window even if modified (set hidden)
+  set hidden
+  enew | only
+  set modified
+  drop Xdropfile
+  call assert_equal(1, winnr('$'))
   " Check for setting the argument list
-  call assert_equal(['Xfile'], argv())
+  call assert_equal(['Xdropfile'], argv())
   enew | only!
-  call delete('Xfile')
 endfunc
 
 " Test for the :append command
diff --git a/test/old/testdir/test_tabpage.vim b/test/old/testdir/test_tabpage.vim
index d3393af04b..d335f3c1ee 100644
--- a/test/old/testdir/test_tabpage.vim
+++ b/test/old/testdir/test_tabpage.vim
@@ -164,6 +164,74 @@ func Test_tabpage_drop()
   bwipe!
   bwipe!
   call assert_equal(1, tabpagenr('$'))
+
+  call assert_equal(1, winnr('$'))
+  call assert_equal('', bufname(''))
+  call writefile(['L1', 'L2'], 'Xdropfile', 'D')
+
+  " Test for ':tab drop single-file': reuse current buffer
+  let expected_nr = bufnr()
+  tab drop Xdropfile
+  call assert_equal(1, tabpagenr('$'))
+  call assert_equal(expected_nr, bufnr())
+  call assert_equal('L2', getline(2))
+  bwipe!
+
+  " Test for ':tab drop single-file': not reuse modified buffer
+  set modified
+  let expected_nr = bufnr() + 1
+  tab drop Xdropfile
+  call assert_equal(2, tabpagenr())
+  call assert_equal(2, tabpagenr('$'))
+  call assert_equal(expected_nr, bufnr())
+  call assert_equal('L2', getline(2))
+  bwipe!
+
+  " Test for ':tab drop single-file': multiple tabs already exist
+  tab split f2
+  tab split f3
+  let expected_nr = bufnr() + 1
+  tab drop Xdropfile
+  call assert_equal(4, tabpagenr())
+  call assert_equal(4, tabpagenr('$'))
+  call assert_equal(expected_nr, bufnr())
+  call assert_equal('L2', getline(2))
+  %bwipe!
+
+  " Test for ':tab drop multi-files': reuse current buffer
+  let expected_nr = bufnr()
+  tab drop Xdropfile f1 f2 f3
+  call assert_equal(1, tabpagenr())
+  call assert_equal(4, tabpagenr('$'))
+  call assert_equal(expected_nr, bufnr())
+  call assert_equal('L2', getline(2))
+  %bwipe!
+
+  " Test for ':tab drop multi-files': not reuse modified buffer
+  set modified
+  let expected_nr = bufnr() + 1
+  tab drop Xdropfile f1 f2 f3
+  call assert_equal(2, tabpagenr())
+  call assert_equal(5, tabpagenr('$'))
+  call assert_equal(expected_nr, bufnr())
+  call assert_equal('L2', getline(2))
+  %bwipe!
+
+  " Test for ':tab drop multi-files': multiple tabs already exist
+  tab split f2
+  tab split f3
+  let expected_nr = bufnr() + 1
+  tab drop a b c
+  call assert_equal(4, tabpagenr())
+  call assert_equal(6, tabpagenr('$'))
+  call assert_equal(expected_nr, bufnr())
+  let expected_nr = bufnr() + 3
+  tab drop Xdropfile f1 f2 f3
+  call assert_equal(5, tabpagenr())
+  call assert_equal(8, tabpagenr('$'))
+  call assert_equal(expected_nr, bufnr())
+  call assert_equal('L2', getline(2))
+  %bwipe!
 endfunc
 
 " Test autocommands
@@ -260,14 +328,14 @@ function Test_tabpage_with_autocmd_tab_drop()
 
   let s:li = []
   tab drop test1
-  call assert_equal(['BufLeave', 'BufEnter'], s:li)
+  call assert_equal(['BufEnter'], s:li)
 
   let s:li = []
   tab drop test2 test3
   call assert_equal([
         \ 'TabLeave', 'TabEnter', 'TabLeave', 'TabEnter',
         \ 'TabLeave', 'WinEnter', 'TabEnter', 'BufEnter',
-        \ 'TabLeave', 'WinEnter', 'TabEnter', 'BufEnter'], s:li)
+        \ 'TabLeave', 'WinEnter', 'TabEnter', 'BufEnter', 'BufEnter'], s:li)
 
   autocmd! TestTabpageGroup
   augroup! TestTabpageGroup