feat(jumplist): allow opting out of removing unloaded buffers

Problem:  Cannot opt out of removing unloaded buffers from the jumplist.
Solution: Only enable that with "unload" flag in 'jumpoptions'.

runtime/doc/options.txt

@@ -3619,7 +3619,7 @@ A jump table for the options with a short description can be found at |Q_op|.
 	Otherwise only one space is inserted.
 
 						*'jumpoptions'* *'jop'*
-'jumpoptions' 'jop'	string	(default "")
+'jumpoptions' 'jop'	string	(default "unload")
 			global
 	List of words that change the behavior of the |jumplist|.
 	  stack         Make the jumplist behave like the tagstack.
@@ -3632,6 +3632,8 @@ A jump table for the options with a short description can be found at |Q_op|.
 			|alternate-file| or using |mark-motions| try to
 			restore the |mark-view| in which the action occurred.
 
+	  unload        Remove unloaded buffers from the jumplist.
+
 						*'keymap'* *'kmp'*
 'keymap' 'kmp'		string	(default "")
 			local to buffer

runtime/doc/vim_diff.txt

@@ -62,6 +62,7 @@ Defaults                                                    *nvim-defaults*
 - 'isfname' does not include ":" (on Windows). Drive letters are handled
   correctly without it. (Use |gF| for filepaths suffixed with ":line:col").
 - 'joinspaces' is disabled
+- 'jumpoptions' defaults to "unload"
 - 'langnoremap' is enabled
 - 'langremap' is disabled
 - 'laststatus' defaults to 2 (statusline is always shown)
@@ -341,6 +342,7 @@ string options work.
 - 'inccommand'  shows interactive results for |:substitute|-like commands
                 and |:command-preview| commands
 - 'jumpoptions' "view" tries to restore the |mark-view| when moving through
+                "unload" removes unloaded buffer from the jumplist
 - the |jumplist|, |changelist|, |alternate-file| or using |mark-motions|.
 - 'laststatus'  global statusline support
 - 'mousescroll' amount to scroll by when scrolling with a mouse

src/nvim/buffer.c

@@ -1396,8 +1396,10 @@ int do_buffer(int action, int start, int dir, int count, int forceit)
 
     // If the buffer to be deleted is not the current one, delete it here.
     if (buf != curbuf) {
-      // Remove the buffer to be deleted from the jump list.
-      buf_remove_from_jumplist(buf);
+      if (jop_flags & JOP_UNLOAD) {
+        // Remove the buffer to be deleted from the jump list.
+        buf_remove_from_jumplist(buf);
+      }
 
       close_windows(buf, false);
 
@@ -1420,28 +1422,37 @@ int do_buffer(int action, int start, int dir, int count, int forceit)
     if (au_new_curbuf.br_buf != NULL && bufref_valid(&au_new_curbuf)) {
       buf = au_new_curbuf.br_buf;
     } else if (curwin->w_jumplistlen > 0) {
-      // Remove the current buffer from the jump list.
-      buf_remove_from_jumplist(curbuf);
+      if (jop_flags & JOP_UNLOAD) {
+        // Remove the current buffer from the jump list.
+        buf_remove_from_jumplist(curbuf);
+      }
 
       // It's possible that we removed all jump list entries, in that case we need to try another
       // approach
       if (curwin->w_jumplistlen > 0) {
-        // If the index is the same as the length, the current position was not yet added to the jump
-        // list. So we can safely go back to the last entry and search from there.
-        if (curwin->w_jumplistidx == curwin->w_jumplistlen) {
-          curwin->w_jumplistidx = curwin->w_jumplistlen - 1;
-        }
-
         int jumpidx = curwin->w_jumplistidx;
 
+        if (jop_flags & JOP_UNLOAD) {
+          // If the index is the same as the length, the current position was not yet added to the
+          // jump list. So we can safely go back to the last entry and search from there.
+          if (jumpidx == curwin->w_jumplistlen) {
+            jumpidx = curwin->w_jumplistidx = curwin->w_jumplistlen - 1;
+          }
+        } else {
+          jumpidx--;
+          if (jumpidx < 0) {
+            jumpidx = curwin->w_jumplistlen - 1;
+          }
+        }
+
         forward = jumpidx;
-        do {
+        while ((jop_flags & JOP_UNLOAD) || jumpidx != curwin->w_jumplistidx) {
           buf = buflist_findnr(curwin->w_jumplist[jumpidx].fmark.fnum);
 
           if (buf != NULL) {
-            // Skip unlisted bufs.  Also skip a quickfix
+            // Skip current and unlisted bufs.  Also skip a quickfix
             // buffer, it might be deleted soon.
-            if (!buf->b_p_bl || bt_quickfix(buf)) {
+            if (buf == curbuf || !buf->b_p_bl || bt_quickfix(buf)) {
               buf = NULL;
             } else if (buf->b_ml.ml_mfp == NULL) {
               // skip unloaded buf, but may keep it for later
@@ -1452,8 +1463,10 @@ int do_buffer(int action, int start, int dir, int count, int forceit)
             }
           }
           if (buf != NULL) {         // found a valid buffer: stop searching
-            curwin->w_jumplistidx = jumpidx;
-            update_jumplist = false;
+            if (jop_flags & JOP_UNLOAD) {
+              curwin->w_jumplistidx = jumpidx;
+              update_jumplist = false;
+            }
             break;
           }
           // advance to older entry in jump list
@@ -1466,7 +1479,7 @@ int do_buffer(int action, int start, int dir, int count, int forceit)
           if (jumpidx == forward) {               // List exhausted for sure
             break;
           }
-        } while (jumpidx != curwin->w_jumplistidx);
+        }
       }
     }
 
@@ -3728,7 +3741,7 @@ void ex_buffer_all(exarg_T *eap)
 
       // Open the buffer in this window.
       swap_exists_action = SEA_DIALOG;
-      set_curbuf(buf, DOBUF_GOTO, false);
+      set_curbuf(buf, DOBUF_GOTO, !(jop_flags & JOP_UNLOAD));
       if (!bufref_valid(&bufref)) {
         // Autocommands deleted the buffer.
         swap_exists_action = SEA_NONE;

src/nvim/option_vars.h

@@ -540,6 +540,7 @@ EXTERN char *p_jop;             ///< 'jumpooptions'
 EXTERN unsigned jop_flags;
 #define JOP_STACK               0x01
 #define JOP_VIEW                0x02
+#define JOP_UNLOAD              0x04
 EXTERN char *p_keymap;          ///< 'keymap'
 EXTERN char *p_kp;              ///< 'keywordprg'
 EXTERN char *p_km;              ///< 'keymodel'

src/nvim/options.lua

@@ -4495,7 +4495,7 @@ return {
     {
       abbreviation = 'jop',
       cb = 'did_set_jumpoptions',
-      defaults = { if_true = '' },
+      defaults = { if_true = 'unload' },
       deny_duplicates = true,
       desc = [=[
         List of words that change the behavior of the |jumplist|.
@@ -4508,6 +4508,8 @@ return {
           view          When moving through the jumplist, |changelist|,
         		|alternate-file| or using |mark-motions| try to
         		restore the |mark-view| in which the action occurred.
+
+          unload        Remove unloaded buffers from the jumplist.
       ]=],
       expand_cb = 'expand_set_jumpoptions',
       full_name = 'jumpoptions',

src/nvim/optionstr.c

@@ -137,7 +137,7 @@ static char *(p_fdc_values[]) = { "auto", "auto:1", "auto:2", "auto:3", "auto:4"
                                   "5", "6", "7", "8", "9", NULL };
 static char *(p_spo_values[]) = { "camel", "noplainbuffer", NULL };
 static char *(p_icm_values[]) = { "nosplit", "split", NULL };
-static char *(p_jop_values[]) = { "stack", "view", NULL };
+static char *(p_jop_values[]) = { "stack", "view", "unload", NULL };
 static char *(p_tpf_values[]) = { "BS", "HT", "FF", "ESC", "DEL", "C0", "C1", NULL };
 static char *(p_rdb_values[]) = { "compositor", "nothrottle", "invalid", "nodelta", "line",
                                   "flush", NULL };

test/functional/editor/jump_spec.lua

@@ -194,7 +194,7 @@ describe("jumpoptions=stack behaves like 'tagstack'", function()
   end)
 end)
 
-describe('buffer deletion', function()
+describe('buffer deletion with jumpoptions+=unload', function()
   local base_file = 'Xtest-functional-buffer-deletion'
   local file1 = base_file .. '1'
   local file2 = base_file .. '2'
@@ -227,6 +227,12 @@ describe('buffer deletion', function()
     command('edit ' .. file3)
   end)
 
+  after_each(function()
+    os.remove(file1)
+    os.remove(file2)
+    os.remove(file3)
+  end)
+
   it('deletes jump list entries when the current buffer is deleted', function()
     command('edit ' .. file1)
 
@@ -319,6 +325,44 @@ describe('buffer deletion', function()
   end)
 end)
 
+describe('buffer deletion with jumpoptions-=unload', function()
+  local base_file = 'Xtest-functional-buffer-deletion'
+  local file1 = base_file .. '1'
+  local file2 = base_file .. '2'
+  local base_content = 'text'
+  local content1 = base_content .. '1'
+  local content2 = base_content .. '2'
+
+  before_each(function()
+    clear()
+    command('clearjumps')
+    command('set jumpoptions-=unload')
+
+    write_file(file1, content1, false, false)
+    write_file(file2, content2, false, false)
+
+    command('edit ' .. file1)
+    command('edit ' .. file2)
+  end)
+
+  after_each(function()
+    os.remove(file1)
+    os.remove(file2)
+  end)
+
+  it('Ctrl-O reopens previous buffer with :bunload or :bdelete #28968', function()
+    eq(file2, fn.bufname(''))
+    command('bunload')
+    eq(file1, fn.bufname(''))
+    feed('<C-O>')
+    eq(file2, fn.bufname(''))
+    command('bdelete')
+    eq(file1, fn.bufname(''))
+    feed('<C-O>')
+    eq(file2, fn.bufname(''))
+  end)
+end)
+
 describe('jumpoptions=view', function()
   local file1 = 'Xtestfile-functional-editor-jumps'
   local file2 = 'Xtestfile-functional-editor-jumps-2'