vim-patch:8.1.0671: cursor in wrong column after auto-format #9729

Problem:    Cursor in the wrong column after auto-formatting.
Solution:   Check for deleting more spaces than adding. (closes vim/vim#3748)
e1e714ef0d

src/nvim/mark.c

@@ -1069,19 +1069,24 @@ static void mark_adjust_internal(linenr_T line1, linenr_T line2,
     { \
       posp->lnum += lnum_amount; \
       assert(col_amount > INT_MIN && col_amount <= INT_MAX); \
-      if (col_amount < 0 && posp->col <= (colnr_T)-col_amount) \
+      if (col_amount < 0 && posp->col <= (colnr_T)-col_amount) { \
         posp->col = 0; \
-      else \
+      } else if (posp->col < spaces_removed) { \
+        posp->col = (int)col_amount + spaces_removed; \
+      } else { \
         posp->col += (colnr_T)col_amount; \
       } \
+    } \
   }
 
-/*
- * Adjust marks in line "lnum" at column "mincol" and further: add
- * "lnum_amount" to the line number and add "col_amount" to the column
- * position.
- */
-void mark_col_adjust(linenr_T lnum, colnr_T mincol, long lnum_amount, long col_amount)
+// Adjust marks in line "lnum" at column "mincol" and further: add
+// "lnum_amount" to the line number and add "col_amount" to the column
+// position.
+// "spaces_removed" is the number of spaces that were removed, matters when the
+// cursor is inside them.
+void mark_col_adjust(
+    linenr_T lnum, colnr_T mincol, long lnum_amount, long col_amount,
+    int spaces_removed)
 {
   int i;
   int fnum = curbuf->b_fnum;

src/nvim/misc1.c

@@ -849,10 +849,11 @@ open_line (
         if (flags & OPENLINE_MARKFIX)
           mark_col_adjust(curwin->w_cursor.lnum,
                           curwin->w_cursor.col + less_cols_off,
-              1L, (long)-less_cols);
-      } else
+                          1L, (long)-less_cols, 0);
+      } else {
         changed_bytes(curwin->w_cursor.lnum, curwin->w_cursor.col);
       }
+    }
 
     /*
      * Put the cursor on the new line.  Careful: the scrollup() above may

src/nvim/ops.c

@@ -3707,10 +3707,16 @@ int do_join(size_t count,
       cend -= spaces[t];
       memset(cend, ' ', (size_t)(spaces[t]));
     }
+
+    // If deleting more spaces than adding, the cursor moves no more than
+    // what is added if it is inside these spaces.
+    const int spaces_removed = (int)((curr - curr_start) - spaces[t]);
+
     mark_col_adjust(curwin->w_cursor.lnum + t, (colnr_T)0, (linenr_T)-t,
-        (long)(cend - newp + spaces[t] - (curr - curr_start)));
-    if (t == 0)
+                    (long)(cend - newp - spaces_removed), spaces_removed);
+    if (t == 0) {
       break;
+    }
     curr = curr_start = ml_get((linenr_T)(curwin->w_cursor.lnum + t - 1));
     if (remove_comments)
       curr += comments[t - 1];
@@ -4138,14 +4144,14 @@ format_lines (
         if (next_leader_len > 0) {
           (void)del_bytes(next_leader_len, false, false);
           mark_col_adjust(curwin->w_cursor.lnum, (colnr_T)0, 0L,
-                          (long)-next_leader_len);
+                          (long)-next_leader_len, 0);
         } else if (second_indent > 0) {   // the "leader" for FO_Q_SECOND
           int indent = (int)getwhitecols_curline();
 
           if (indent > 0) {
             (void)del_bytes(indent, FALSE, FALSE);
             mark_col_adjust(curwin->w_cursor.lnum,
-                (colnr_T)0, 0L, (long)-indent);
+                            (colnr_T)0, 0L, (long)-indent, 0);
           }
         }
         curwin->w_cursor.lnum--;

src/nvim/testdir/test_textformat.vim

@@ -450,5 +450,16 @@ func Test_format_undo()
 	      \ ], getline(1, '$'))
 
   unmap gg
+  set tw&
   enew!
 endfunc
+
+func Test_format_list_auto()
+  new
+  call setline(1, ['1. abc', '2. def', '3.  ghi'])
+  set fo=tan ai bs=2
+  call feedkeys("3G0lli\<BS>\<BS>x\<Esc>", 'tx')
+  call assert_equal('2. defx ghi', getline(2))
+  bwipe!
+  set fo& ai& bs&
+endfunc