vim-patch:9.1.0537: signed number detection for CTRL-X/A can be improved (#29590)

Problem:  signed number detection for CTRL-X/A can be improved
          (Chris Patuzzo)
Solution: Add the new "blank" value for the 'nrformat' setting. This
          will make Vim assume a signed number only if there is a blank
          in front of the sign.
          (distobs)

fixes: vim/vim#15033
closes: vim/vim#15110

https://github.com/vim/vim/commit/25ac6d67d92e0adda53b8d44b81c15031643ca1e

Co-authored-by: distobs <cuppotatocake@gmail.com>

3 files changed, 36 insertions, 13 deletions

diff --git a/src/nvim/ops.c b/src/nvim/ops.c
index 7bffb12412..f2f8708235 100644
--- a/src/nvim/ops.c
+++ b/src/nvim/ops.c
@@ -4420,6 +4420,7 @@ bool do_addsub(int op_type, pos_T *pos, int length, linenr_T Prenum1)
   int pre;  // 'X' or 'x': hex; '0': octal; 'B' or 'b': bin
   static bool hexupper = false;  // 0xABC
   uvarnumber_T n;
+  bool blank_unsigned = false;  // blank: treat as unsigned?
   bool negative = false;
   bool was_positive = true;
   bool visual = VIsual_active;
@@ -4430,12 +4431,12 @@ bool do_addsub(int op_type, pos_T *pos, int length, linenr_T Prenum1)
   pos_T endpos;
   colnr_T save_coladd = 0;
 
-  const bool do_hex = vim_strchr(curbuf->b_p_nf, 'x') != NULL;    // "heX"
-  const bool do_oct = vim_strchr(curbuf->b_p_nf, 'o') != NULL;    // "Octal"
-  const bool do_bin = vim_strchr(curbuf->b_p_nf, 'b') != NULL;    // "Bin"
-  const bool do_alpha = vim_strchr(curbuf->b_p_nf, 'p') != NULL;  // "alPha"
-  // "Unsigned"
-  const bool do_unsigned = vim_strchr(curbuf->b_p_nf, 'u') != NULL;
+  const bool do_hex = vim_strchr(curbuf->b_p_nf, 'x') != NULL;       // "heX"
+  const bool do_oct = vim_strchr(curbuf->b_p_nf, 'o') != NULL;       // "Octal"
+  const bool do_bin = vim_strchr(curbuf->b_p_nf, 'b') != NULL;       // "Bin"
+  const bool do_alpha = vim_strchr(curbuf->b_p_nf, 'p') != NULL;     // "alPha"
+  const bool do_unsigned = vim_strchr(curbuf->b_p_nf, 'u') != NULL;  // "Unsigned"
+  const bool do_blank = vim_strchr(curbuf->b_p_nf, 'k') != NULL;     // "blanK"
 
   if (virtual_active(curwin)) {
     save_coladd = pos->coladd;
@@ -4532,8 +4533,12 @@ bool do_addsub(int op_type, pos_T *pos, int length, linenr_T Prenum1)
     if (col > pos->col && ptr[col - 1] == '-'
         && !utf_head_off(ptr, ptr + col - 1)
         && !do_unsigned) {
-      negative = true;
-      was_positive = false;
+      if (do_blank && col >= 2 && !ascii_iswhite(ptr[col - 2])) {
+        blank_unsigned = true;
+      } else {
+        negative = true;
+        was_positive = false;
+      }
     }
   }
 
@@ -4579,9 +4584,13 @@ bool do_addsub(int op_type, pos_T *pos, int length, linenr_T Prenum1)
         && !utf_head_off(ptr, ptr + col - 1)
         && !visual
         && !do_unsigned) {
-      // negative number
-      col--;
-      negative = true;
+      if (do_blank && col >= 2 && !ascii_iswhite(ptr[col - 2])) {
+        blank_unsigned = true;
+      } else {
+        // negative number
+        col--;
+        negative = true;
+      }
     }
 
     // get the number value (unsigned)
@@ -4638,7 +4647,7 @@ bool do_addsub(int op_type, pos_T *pos, int length, linenr_T Prenum1)
       }
     }
 
-    if (do_unsigned && negative) {
+    if ((do_unsigned || blank_unsigned) && negative) {
       if (subtract) {
         // sticking at zero.
         n = 0;
diff --git a/src/nvim/options.lua b/src/nvim/options.lua
index 365679261c..6e317a426c 100644
--- a/src/nvim/options.lua
+++ b/src/nvim/options.lua
@@ -5717,6 +5717,20 @@ return {
         	    (without "unsigned" it would become "9-2019").
         	    Using CTRL-X on "0" or CTRL-A on "18446744073709551615"
         	    (2^64 - 1) has no effect, overflow is prevented.
+        blank	If included, treat numbers as signed or unsigned based on
+        	preceding whitespace. If a number with a leading dash has its
+        	dash immediately preceded by a non-whitespace character (i.e.,
+        	not a tab or a " "), the negative sign won't be considered as
+        	part of the number.  For example:
+        	    Using CTRL-A on "14" in "Carbon-14" results in "Carbon-15"
+        	    (without "blank" it would become "Carbon-13").
+        	    Using CTRL-X on "8" in "Carbon -8" results in "Carbon -9"
+        	    (because -8 is preceded by whitespace. If "unsigned" was
+        	    set, it would result in "Carbon -7").
+        	If this format is included, overflow is prevented as if
+        	"unsigned" were set. If both this format and "unsigned" are
+        	included, "unsigned" will take precedence.
+
         Numbers which simply begin with a digit in the range 1-9 are always
         considered decimal.  This also happens for numbers that are not
         recognized as octal or hex.
diff --git a/src/nvim/optionstr.c b/src/nvim/optionstr.c
index cdbb8c2d6d..1a4c142fdd 100644
--- a/src/nvim/optionstr.c
+++ b/src/nvim/optionstr.c
@@ -82,7 +82,7 @@ static char *(p_dip_values[]) = { "filler", "context:", "iblank", "icase",
                                   "closeoff", "hiddenoff", "foldcolumn:", "followwrap", "internal",
                                   "indent-heuristic", "linematch:", "algorithm:", NULL };
 static char *(p_dip_algorithm_values[]) = { "myers", "minimal", "patience", "histogram", NULL };
-static char *(p_nf_values[]) = { "bin", "octal", "hex", "alpha", "unsigned", NULL };
+static char *(p_nf_values[]) = { "bin", "octal", "hex", "alpha", "unsigned", "blank", NULL };
 static char *(p_ff_values[]) = { FF_UNIX, FF_DOS, FF_MAC, NULL };
 static char *(p_cb_values[]) = { "unnamed", "unnamedplus", NULL };
 static char *(p_cmp_values[]) = { "internal", "keepascii", NULL };