patch 9.1.0785: cannot preserve error position when setting quickfix list

Problem:  cannot preserve error position when setting quickfix lists
Solution: Add the 'u' action for setqflist()/setloclist() and try
          to keep the closes target position (Jeremy Fleischman)

fixes: #15839
closes: #15841

Signed-off-by: Jeremy Fleischman <jeremyfleischman@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>

runtime/doc/builtin.txt

@@ -1,4 +1,4 @@
-*builtin.txt*	For Vim version 9.1.  Last change: 2024 Oct 12
+*builtin.txt*	For Vim version 9.1.  Last change: 2024 Oct 14
 
 
 		  VIM REFERENCE MANUAL	  by Bram Moolenaar
@@ -9766,6 +9766,8 @@ setqflist({list} [, {action} [, {what}]])		*setqflist()*
 			clear the list: >
 				:call setqflist([], 'r')
 <
+		'u'	Like 'r', but tries to preserve the current selection
+			in the quickfix list.
 		'f'	All the quickfix lists in the quickfix stack are
 			freed.
 

runtime/doc/version9.txt

@@ -1,4 +1,4 @@
-*version9.txt*  For Vim version 9.1.  Last change: 2024 Oct 08
+*version9.txt*  For Vim version 9.1.  Last change: 2024 Oct 14
 
 
 		  VIM REFERENCE MANUAL    by Bram Moolenaar
@@ -41598,6 +41598,8 @@ Changed~
 - the regex engines match correctly case-insensitive multi-byte characters
   (and apply proper case folding)
 - |:keeppatterns| preserves the last substitute pattern when used with |:s|
+- |setqflist()| and |setloclist()| can optionally try to preserve the current
+  selection in the quickfix list with the "u" action.
 
 							*added-9.2*
 Added ~

src/quickfix.c

@@ -190,6 +190,7 @@ static buf_T	*load_dummy_buffer(char_u *fname, char_u *dirname_start, char_u *re
 static void	wipe_dummy_buffer(buf_T *buf, char_u *dirname_start);
 static void	unload_dummy_buffer(buf_T *buf, char_u *dirname_start);
 static qf_info_T *ll_get_or_alloc_list(win_T *);
+static int	entry_is_closer_to_target(qfline_T *entry, qfline_T *other_entry, int target_fnum, int target_lnum, int target_col);
 
 // Quickfix window check helper macro
 #define IS_QF_WINDOW(wp) (bt_quickfix((wp)->w_buffer) && (wp)->w_llist_ref == NULL)
@@ -7499,6 +7500,62 @@ qf_add_entry_from_dict(
     return status;
 }
 
+/*
+ * Check if `entry` is closer to the target than `other_entry`.
+ *
+ * Only returns TRUE if `entry` is definitively closer. If it's further
+ * away, or there's not enough information to tell, return FALSE.
+ */
+    static int
+entry_is_closer_to_target(
+	qfline_T	*entry,
+	qfline_T	*other_entry,
+	int		target_fnum,
+	int		target_lnum,
+	int		target_col)
+{
+    // First, compare entries to target file.
+    if (!target_fnum)
+	// Without a target file, we can't know which is closer.
+	return FALSE;
+
+    int is_target_file = entry->qf_fnum && entry->qf_fnum == target_fnum;
+    int other_is_target_file = other_entry->qf_fnum && other_entry->qf_fnum == target_fnum;
+    if (!is_target_file && other_is_target_file)
+	return FALSE;
+    else if (is_target_file && !other_is_target_file)
+	return TRUE;
+
+    // Both entries are pointing at the exact same file. Now compare line
+    // numbers.
+    if (!target_lnum)
+	// Without a target line number, we can't know which is closer.
+	return FALSE;
+
+    int line_distance = entry->qf_lnum ? labs(entry->qf_lnum - target_lnum) : INT_MAX;
+    int other_line_distance = other_entry->qf_lnum ? labs(other_entry->qf_lnum - target_lnum) : INT_MAX;
+    if (line_distance > other_line_distance)
+	return FALSE;
+    else if (line_distance < other_line_distance)
+	return TRUE;
+
+    // Both entries are pointing at the exact same line number (or no line
+    // number at all). Now compare columns.
+    if (!target_col)
+	// Without a target column, we can't know which is closer.
+	return FALSE;
+
+    int column_distance = entry->qf_col ? abs(entry->qf_col - target_col) : INT_MAX;
+    int other_column_distance = other_entry->qf_col ? abs(other_entry->qf_col - target_col): INT_MAX;
+    if (column_distance > other_column_distance)
+	return FALSE;
+    else if (column_distance < other_column_distance)
+	return TRUE;
+
+    // It's a complete tie! The exact same file, line, and column.
+    return FALSE;
+}
+
 /*
  * Add list of entries to quickfix/location list. Each list entry is
  * a dictionary with item information.
@@ -7518,21 +7575,54 @@ qf_add_entries(
     int		retval = OK;
     int		valid_entry = FALSE;
 
+    // If there's an entry selected in the quickfix list, remember its location
+    // (file, line, column), so we can select the nearest entry in the updated
+    // quickfix list.
+    int prev_fnum = 0;
+    int prev_lnum = 0;
+    int prev_col = 0;
+    if (qfl->qf_ptr)
+    {
+	prev_fnum = qfl->qf_ptr->qf_fnum;
+	prev_lnum = qfl->qf_ptr->qf_lnum;
+	prev_col = qfl->qf_ptr->qf_col;
+    }
+
+    int select_first_entry = FALSE;
+    int select_nearest_entry = FALSE;
+
     if (action == ' ' || qf_idx == qi->qf_listcount)
     {
+	select_first_entry = TRUE;
 	// make place for a new list
 	qf_new_list(qi, title);
 	qf_idx = qi->qf_curlist;
 	qfl = qf_get_list(qi, qf_idx);
     }
-    else if (action == 'a' && !qf_list_empty(qfl))
+    else if (action == 'a')
+    {
+	if (qf_list_empty(qfl))
+	    // Appending to empty list, select first entry.
+	    select_first_entry = TRUE;
+	else
 	    // Adding to existing list, use last entry.
 	    old_last = qfl->qf_last;
+    }
     else if (action == 'r')
     {
+	select_first_entry = TRUE;
 	qf_free_items(qfl);
 	qf_store_title(qfl, title);
     }
+    else if (action == 'u')
+    {
+	select_nearest_entry = TRUE;
+	qf_free_items(qfl);
+	qf_store_title(qfl, title);
+    }
+
+    qfline_T *entry_to_select = NULL;
+    int entry_to_select_index = 0;
 
     FOR_ALL_LIST_ITEMS(list, li)
     {
@@ -7547,6 +7637,18 @@ qf_add_entries(
 								&valid_entry);
 	if (retval == QF_FAIL)
 	    break;
+
+	qfline_T *entry = qfl->qf_last;
+	if (
+	    (select_first_entry && entry_to_select == NULL) ||
+	    (select_nearest_entry &&
+		(entry_to_select == NULL ||
+		 entry_is_closer_to_target(entry, entry_to_select, prev_fnum,
+					   prev_lnum, prev_col))))
+	{
+	    entry_to_select = entry;
+	    entry_to_select_index = qfl->qf_count;
+        }
     }
 
     // Check if any valid error entries are added to the list.
@@ -7556,14 +7658,12 @@ qf_add_entries(
 	// no valid entry
 	qfl->qf_nonevalid = TRUE;
 
-    // If not appending to the list, set the current error to the first entry
+    // Set the current error.
-    if (action != 'a')
+    if (entry_to_select)
-	qfl->qf_ptr = qfl->qf_start;
+    {
-
+	qfl->qf_ptr = entry_to_select;
-    // Update the current error index if not appending to the list or if the
+	qfl->qf_index = entry_to_select_index;
-    // list was empty before and it is not empty now.
+    }
-    if ((action != 'a' || qfl->qf_index == 0) && !qf_list_empty(qfl))
-	qfl->qf_index = 1;
 
     // Don't update the cursor in quickfix window when appending entries
     qf_update_buffer(qi, old_last);
@@ -7700,7 +7800,7 @@ qf_setprop_items_from_lines(
     if (di->di_tv.v_type != VAR_LIST || di->di_tv.vval.v_list == NULL)
 	return FAIL;
 
-    if (action == 'r')
+    if (action == 'r' || action == 'u')
 	qf_free_items(&qi->qf_lists[qf_idx]);
     if (qf_init_ext(qi, qf_idx, NULL, NULL, &di->di_tv, errorformat,
 		FALSE, (linenr_T)0, (linenr_T)0, NULL, NULL) >= 0)
@@ -7897,8 +7997,8 @@ qf_free_stack(win_T *wp, qf_info_T *qi)
 /*
  * Populate the quickfix list with the items supplied in the list
  * of dictionaries. "title" will be copied to w:quickfix_title.
- * "action" is 'a' for add, 'r' for replace.  Otherwise create a new list.
+ * "action" is 'a' for add, 'r' for replace, 'u' for update.  Otherwise
- * When "what" is not NULL then only set some properties.
+ * create a new list. When "what" is not NULL then only set some properties.
  */
     int
 set_errorlist(
@@ -8740,7 +8840,7 @@ set_qf_ll_list(
 	    act = tv_get_string_chk(action_arg);
 	    if (act == NULL)
 		return;		// type error; errmsg already given
-	    if ((*act == 'a' || *act == 'r' || *act == ' ' || *act == 'f') &&
+	    if ((*act == 'a' || *act == 'r' || *act == 'u' || *act == ' ' || *act == 'f') &&
 		    act[1] == NUL)
 		action = *act;
 	    else

src/testdir/test_quickfix.vim

@@ -6462,6 +6462,97 @@ func Test_quickfix_buffer_contents()
   call setqflist([], 'f')
 endfunc
 
+func Test_quickfix_update()
+  " Setup: populate a couple buffers
+  new
+  call setline(1, range(1, 5))
+  let b1 = bufnr()
+  new
+  call setline(1, range(1, 3))
+  let b2 = bufnr()
+  " Setup: set a quickfix list.
+  let items = [{'bufnr': b1, 'lnum': 1}, {'bufnr': b1, 'lnum': 2}, {'bufnr': b2, 'lnum': 1}, {'bufnr': b2, 'lnum': 2}]
+  call setqflist(items)
+
+  " Open the quickfix list, select the third entry.
+  copen
+  exe "normal jj\<CR>"
+  call assert_equal(3, getqflist({'idx' : 0}).idx)
+
+  " Update the quickfix list. Make sure the third entry is still selected.
+  call setqflist([], 'u', { 'items': items })
+  call assert_equal(3, getqflist({'idx' : 0}).idx)
+
+  " Update the quickfix list again, but this time with missing line number
+  " information. Confirm that we keep the current buffer selected.
+  call setqflist([{'bufnr': b1}, {'bufnr': b2}], 'u')
+  call assert_equal(2, getqflist({'idx' : 0}).idx)
+
+  " Cleanup the buffers we allocated during this test.
+  %bwipe!
+  %bwipe!
+endfunc
+
+func Test_quickfix_update_with_missing_coordinate_info()
+  new
+  call setline(1, range(1, 5))
+  let b1 = bufnr()
+
+  new
+  call setline(1, range(1, 3))
+  let b2 = bufnr()
+
+  new
+  call setline(1, range(1, 2))
+  let b3 = bufnr()
+
+  " Setup: set a quickfix list with no coordinate information at all.
+  call setqflist([{}, {}])
+
+  " Open the quickfix list, select the second entry.
+  copen
+  exe "normal j\<CR>"
+  call assert_equal(2, getqflist({'idx' : 0}).idx)
+
+  " Update the quickfix list. As the previously selected entry has no
+  " coordinate information, we expect the first entry to now be selected.
+  call setqflist([{'bufnr': b1}, {'bufnr': b2}, {'bufnr': b3}], 'u')
+  call assert_equal(1, getqflist({'idx' : 0}).idx)
+
+  " Select the second entry in the quickfix list.
+  copen
+  exe "normal j\<CR>"
+  call assert_equal(2, getqflist({'idx' : 0}).idx)
+
+  " Update the quickfix list again. The currently selected entry does not have
+  " a line number, but we should keep the file selected.
+  call setqflist([{'bufnr': b1}, {'bufnr': b2, 'lnum': 3}, {'bufnr': b3}], 'u')
+  call assert_equal(2, getqflist({'idx' : 0}).idx)
+
+  " Update the quickfix list again. The currently selected entry (bufnr=b2, lnum=3)
+  " is no longer present. We should pick the nearest entry.
+  call setqflist([{'bufnr': b1}, {'bufnr': b2, 'lnum': 1}, {'bufnr': b2, 'lnum': 4}], 'u')
+  call assert_equal(3, getqflist({'idx' : 0}).idx)
+
+  " Set the quickfix list again, with a specific column number. The currently selected entry doesn't have a
+  " column number, but they share a line number.
+  call setqflist([{'bufnr': b1}, {'bufnr': b2, 'lnum': 4, 'col': 5}, {'bufnr': b2, 'lnum': 4, 'col': 6}], 'u')
+  call assert_equal(2, getqflist({'idx' : 0}).idx)
+
+  " Set the quickfix list again. The currently selected column number (6) is
+  " no longer present. We should select the nearest column number.
+  call setqflist([{'bufnr': b1}, {'bufnr': b2, 'lnum': 4, 'col': 2}, {'bufnr': b2, 'lnum': 4, 'col': 4}], 'u')
+  call assert_equal(3, getqflist({'idx' : 0}).idx)
+
+  " Now set the quickfix list, but without columns. We should still pick the
+  " same line.
+  call setqflist([{'bufnr': b2, 'lnum': 3}, {'bufnr': b2, 'lnum': 4}, {'bufnr': b2, 'lnum': 4}], 'u')
+  call assert_equal(2, getqflist({'idx' : 0}).idx)
+
+  " Cleanup the buffers we allocated during this test.
+  %bwipe!
+endfunc
+
 " Test for "%b" in "errorformat"
 func Test_efm_format_b()
   call setqflist([], 'f')

src/version.c

@@ -704,6 +704,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    785,
 /**/
     784,
 /**/