patch 9.0.1686: undotree() only works for the current buffer

Problem:    undotree() only works for the current buffer
Solution:   Add an optional "buffer number" parameter to undotree().  If
            omitted, use the current buffer for backwards compatibility.

closes: #4001
closes: #12292

Signed-off-by: Christian Brabandt <cb@256bit.org>
Co-authored-by: zeertzjq <zeertzjq@outlook.com>
Co-authored-by: Devin J. Pohly <djpohly@gmail.com>

runtime/doc/builtin.txt

@@ -707,7 +707,7 @@ trunc({expr})			Float	truncate Float {expr}
 type({expr})			Number	type of value {expr}
 typename({expr})		String	representation of the type of {expr}
 undofile({name})		String	undo file name for {name}
-undotree()			List	undo file tree
+undotree([{buf}])		List	undo file tree for buffer {buf}
 uniq({list} [, {func} [, {dict}]])
 				List	remove adjacent duplicates from a list
 utf16idx({string}, {idx} [, {countcc} [, {charidx}]])
@@ -10073,9 +10073,10 @@ undofile({name})					*undofile()*
 		Can also be used as a |method|: >
 			GetFilename()->undofile()
 
-undotree()						*undotree()*
+undotree([{buf}])					*undotree()*
-		Return the current state of the undo tree in a dictionary with
+		Return the current state of the undo tree for the current
-		the following items:
+		buffer, or for a specific buffer if {buf} is given.  The
+		result is a dictionary with the following items:
 		  "seq_last"	The highest undo sequence number used.
 		  "seq_cur"	The sequence number of the current position in
 				the undo tree.  This differs from "seq_last"

runtime/doc/todo.txt

@@ -5535,7 +5535,6 @@ Undo:
 -   Undo history wrong when ":next file" re-uses a buffer. (#5426) ex_next()
     should pass flag to do_argfile(), then to do_ecmd().  Is there a test for
     this?
--   Add buffer argument to undotree(). (#4001)
 -   Undo problem: "g-" doesn't go back, gets stuck. (Björn Linse, 2016 Jul 18)
 -   Undo message is not always properly displayed.  Patch by Ken Takata, 2013
     oct 3.  Doesn't work properly according to Yukihiro Nakadaira.

runtime/doc/usr_41.txt

@@ -1373,7 +1373,7 @@ Various:					*various-functions*
 	libcallnr()		idem, returning a number
 
 	undofile()		get the name of the undo file
-	undotree()		return the state of the undo tree
+	undotree()		return the state of the undo tree for a buffer
 
 	shiftwidth()		effective value of 'shiftwidth'
 

src/evalfunc.c

@@ -2798,7 +2798,7 @@ static funcentry_T global_functions[] =
 			ret_string,	    f_typename},
     {"undofile",	1, 1, FEARG_1,	    arg1_string,
 			ret_string,	    f_undofile},
-    {"undotree",	0, 0, 0,	    NULL,
+    {"undotree",	0, 1, FEARG_1,	    arg1_buffer,
 			ret_dict_any,	    f_undotree},
     {"uniq",		1, 3, FEARG_1,	    arg13_sortuniq,
 			ret_first_arg,	    f_uniq},

src/testdir/test_undo.vim

@@ -93,6 +93,53 @@ func FillBuffer()
   endfor
 endfunc
 
+func Test_undotree_bufnr()
+  new
+  let buf1 = bufnr()
+
+  normal! Aabc
+  set ul=100
+
+  " Save undo tree without bufnr as ground truth for buffer 1
+  let d1 = undotree()
+
+  new
+  let buf2 = bufnr()
+
+  normal! Adef
+  set ul=100
+
+  normal! Aghi
+  set ul=100
+
+  " Save undo tree without bufnr as ground truth for buffer 2
+  let d2 = undotree()
+
+  " Check undotree() with bufnr argument
+  let d = undotree(buf1)
+  call assert_equal(d1, d)
+  call assert_notequal(d2, d)
+
+  let d = undotree(buf2)
+  call assert_notequal(d1, d)
+  call assert_equal(d2, d)
+
+  " Switch buffers and check again
+  wincmd p
+
+  let d = undotree(buf1)
+  call assert_equal(d1, d)
+
+  let d = undotree(buf2)
+  call assert_notequal(d1, d)
+  call assert_equal(d2, d)
+
+  " Drop created windows
+  set ul&
+  new
+  only!
+endfunc
+
 func Test_global_local_undolevels()
   new one
   set undolevels=5

src/undo.c

@@ -3629,7 +3629,7 @@ curbufIsChanged(void)
  * Recursive.
  */
     static void
-u_eval_tree(u_header_T *first_uhp, list_T *list)
+u_eval_tree(buf_T *buf, u_header_T *first_uhp, list_T *list)
 {
     u_header_T  *uhp = first_uhp;
     dict_T	*dict;
@@ -3641,9 +3641,9 @@ u_eval_tree(u_header_T *first_uhp, list_T *list)
 	    return;
 	dict_add_number(dict, "seq", uhp->uh_seq);
 	dict_add_number(dict, "time", (long)uhp->uh_time);
-	if (uhp == curbuf->b_u_newhead)
+	if (uhp == buf->b_u_newhead)
 	    dict_add_number(dict, "newhead", 1);
-	if (uhp == curbuf->b_u_curhead)
+	if (uhp == buf->b_u_curhead)
 	    dict_add_number(dict, "curhead", 1);
 	if (uhp->uh_save_nr > 0)
 	    dict_add_number(dict, "save", uhp->uh_save_nr);
@@ -3655,7 +3655,7 @@ u_eval_tree(u_header_T *first_uhp, list_T *list)
 	    if (alt_list != NULL)
 	    {
 		// Recursive call to add alternate undo tree.
-		u_eval_tree(uhp->uh_alt_next.ptr, alt_list);
+		u_eval_tree(buf, uhp->uh_alt_next.ptr, alt_list);
 		dict_add_list(dict, "alt", alt_list);
 	    }
 	}
@@ -3721,28 +3721,40 @@ u_undofile_reset_and_delete(buf_T *buf)
  #endif
 
 /*
- * "undotree()" function
+ * "undotree(expr)" function
  */
     void
 f_undotree(typval_T *argvars UNUSED, typval_T *rettv)
 {
+    typval_T	*tv = &argvars[0];
+    buf_T	*buf;
+    dict_T	*dict;
+    list_T	*list;
+
+    if (in_vim9script() && check_for_opt_buffer_arg(argvars, 0) == FAIL)
+	return;
+
+    if (tv->v_type == VAR_UNKNOWN)
+	buf = curbuf;
+    else
+	buf = tv_get_buf_from_arg(tv);
+
     if (rettv_dict_alloc(rettv) == FAIL)
 	return;
 
-    dict_T *dict = rettv->vval.v_dict;
+    dict = rettv->vval.v_dict;
-    list_T *list;
 
-    dict_add_number(dict, "synced", (long)curbuf->b_u_synced);
+    dict_add_number(dict, "synced", (long)buf->b_u_synced);
-    dict_add_number(dict, "seq_last", curbuf->b_u_seq_last);
+    dict_add_number(dict, "seq_last", buf->b_u_seq_last);
-    dict_add_number(dict, "save_last", curbuf->b_u_save_nr_last);
+    dict_add_number(dict, "save_last", buf->b_u_save_nr_last);
-    dict_add_number(dict, "seq_cur", curbuf->b_u_seq_cur);
+    dict_add_number(dict, "seq_cur", buf->b_u_seq_cur);
-    dict_add_number(dict, "time_cur", (long)curbuf->b_u_time_cur);
+    dict_add_number(dict, "time_cur", (long)buf->b_u_time_cur);
-    dict_add_number(dict, "save_cur", curbuf->b_u_save_nr_cur);
+    dict_add_number(dict, "save_cur", buf->b_u_save_nr_cur);
 
     list = list_alloc();
     if (list != NULL)
     {
-	u_eval_tree(curbuf->b_u_oldhead, list);
+	u_eval_tree(buf, buf->b_u_oldhead, list);
 	dict_add_list(dict, "entries", list);
     }
 }

src/version.c

@@ -695,6 +695,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1686,
 /**/
     1685,
 /**/