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>

6 files changed, 93 insertions, 15 deletions

diff --git a/src/nvim/arglist.c b/src/nvim/arglist.c
index 921d56ed78..e9108f72cc 100644
--- a/src/nvim/arglist.c
+++ b/src/nvim/arglist.c
@@ -477,7 +477,7 @@ static int do_arglist(char *str, int what, int after, bool will_edit)
 /// Redefine the argument list.
 void set_arglist(char *str)
 {
-  do_arglist(str, AL_SET, 0, false);
+  do_arglist(str, AL_SET, 0, true);
 }
 
 /// @return  true if window "win" is editing the file at the current argument
diff --git a/src/nvim/ex_cmds2.c b/src/nvim/ex_cmds2.c
index 234a927291..842f8a4297 100644
--- a/src/nvim/ex_cmds2.c
+++ b/src/nvim/ex_cmds2.c
@@ -799,8 +799,7 @@ static void script_host_do_range(char *name, exarg_T *eap)
 }
 
 /// ":drop"
-/// Opens the first argument in a window.  When there are two or more arguments
-/// the argument list is redefined.
+/// Opens the first argument in a window, and the argument list is redefined.
 void ex_drop(exarg_T *eap)
 {
   bool split = false;
@@ -825,6 +824,8 @@ void ex_drop(exarg_T *eap)
     // edited in a window yet.  It's like ":tab all" but without closing
     // windows or tabs.
     ex_all(eap);
+    cmdmod.cmod_tab = 0;
+    ex_rewind(eap);
     return;
   }
 
@@ -845,6 +846,7 @@ void ex_drop(exarg_T *eap)
         buf_check_timestamp(curbuf);
         curbuf->b_p_ar = save_ar;
       }
+      ex_rewind(eap);
       return;
     }
   }
diff --git a/test/functional/core/remote_spec.lua b/test/functional/core/remote_spec.lua
index a48534f51b..caff06f6ab 100644
--- a/test/functional/core/remote_spec.lua
+++ b/test/functional/core/remote_spec.lua
@@ -81,7 +81,7 @@ describe('Remote', function()
     it('edit a single file', function()
       eq({ '', '' }, run_remote('--remote', fname))
       expect(contents)
-      eq(2, #fn.getbufinfo())
+      eq(1, #fn.getbufinfo())
     end)
 
     it('tab edit a single file with a non-changed buffer', function()
@@ -102,7 +102,7 @@ describe('Remote', function()
       expect(contents)
       command('next')
       expect(other_contents)
-      eq(3, #fn.getbufinfo())
+      eq(2, #fn.getbufinfo())
     end)
 
     it('send keys', function()
diff --git a/test/functional/ex_cmds/drop_spec.lua b/test/functional/ex_cmds/drop_spec.lua
index c78928f7a1..cbda5aac98 100644
--- a/test/functional/ex_cmds/drop_spec.lua
+++ b/test/functional/ex_cmds/drop_spec.lua
@@ -38,7 +38,7 @@ describe(':drop', function()
                     │^                    |
       {0:~             }│{0:~                   }|*7
       {2:tmp2           }{1:tmp1                }|
-      :drop tmp1                         |
+      "tmp1" [New]                       |
     ]])
   end)
 
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