vim-patch:8.2.3198: cannot use 'formatlistpat' for breakindent

Problem:    Cannot use 'formatlistpat' for breakindent.
Solution:   Use a negative list indent. (Maxim Kim, closes vim/vim#8594)
f674b358fc

Port get_showbreak_value() from patch v8.1.2281
to avoid breaking changes when porting older patches.

runtime/doc/options.txt

@@ -1041,6 +1041,8 @@ A jump table for the options with a short description can be found at |Q_op|.
 		list:{n}    Adds an additional indent for lines that match a
 			    numbered or bulleted list (using the
 			    'formatlistpat' setting).
+		list:-1	    Uses the length of a match with 'formatlistpat'
+			    for indentation.
 	The default value for min is 20, shift and list is 0.
 
 						*'browsedir'* *'bsdir'*

src/nvim/indent.c

@@ -462,15 +462,11 @@ int get_breakindent_win(win_T *wp, char_u *line)
   }
   bri = prev_indent + wp->w_briopt_shift;
 
-  // indent minus the length of the showbreak string
-  if (wp->w_briopt_sbr) {
-    bri -= vim_strsize(p_sbr);
-  }
   // Add offset for number column, if 'n' is in 'cpoptions'
   bri += win_col_off2(wp);
 
   // add additional indent for numbered lists
-  if (wp->w_briopt_list > 0) {
+  if (wp->w_briopt_list != 0) {
     regmatch_T regmatch = {
       .regprog = vim_regcomp(curbuf->b_p_flp,
                              RE_MAGIC + RE_STRING + RE_AUTO + RE_STRICT),
@@ -478,12 +474,20 @@ int get_breakindent_win(win_T *wp, char_u *line)
 
     if (regmatch.regprog != NULL) {
       if (vim_regexec(&regmatch, line, 0)) {
-        bri += wp->w_briopt_list;
+        if (wp->w_briopt_list > 0) {
+          bri += wp->w_briopt_list;
+        } else {
+          bri = (int)(*regmatch.endp - *regmatch.startp);
+        }
       }
       vim_regfree(regmatch.regprog);
     }
   }
 
+  // indent minus the length of the showbreak string
+  if (wp->w_briopt_sbr) {
+    bri -= vim_strsize(get_showbreak_value(wp));
+  }
 
   // never indent past left window margin
   if (bri < 0) {

src/nvim/option.c

@@ -7674,6 +7674,12 @@ int win_signcol_configured(win_T *wp, int *is_fixed)
   return ret;
 }
 
+// Get the local or global value of 'showbreak'.
+char_u *get_showbreak_value(win_T *win FUNC_ATTR_UNUSED)
+{
+  return p_sbr;
+}
+
 /// Get window or buffer local options
 dict_T *get_winbuf_options(const int bufopt)
   FUNC_ATTR_WARN_UNUSED_RESULT

src/nvim/testdir/test_breakindent.vim

@@ -796,6 +796,7 @@ func Test_breakindent20_list()
 	\ ]
   let lines = s:screen_lines2(1, 9, 20)
   call s:compare_lines(expect, lines)
+
   " reset linebreak option
   " Note: it indents by one additional
   " space, because of the leading space.
@@ -812,7 +813,59 @@ func Test_breakindent20_list()
   let lines = s:screen_lines2(1, 6, 20)
   call s:compare_lines(expect, lines)
 
-  call s:close_windows('set breakindent& briopt& linebreak& list& listchars&')
+  " check formatlistpat indent
+  setl briopt=min:5,list:-1
+  setl linebreak list&vim listchars&vim
+  let &l:flp = '^\s*\d\+\.\?[\]:)}\t ]\s*'
+  redraw!
+  let expect = [
+	\ "  1.  Congress      ",
+	\ "      shall make no ",
+	\ "      law           ",
+	\ "  2.) Congress      ",
+	\ "      shall make no ",
+	\ "      law           ",
+	\ "  3.] Congress      ",
+	\ "      shall make no ",
+	\ "      law           ",
+	\ ]
+  let lines = s:screen_lines2(1, 9, 20)
+  call s:compare_lines(expect, lines)
+  " check formatlistpat indent with different list levels
+  let &l:flp = '^\s*\*\+\s\+'
+  redraw!
+  %delete _
+  call setline(1, ['* Congress shall make no law',
+        \ '*** Congress shall make no law',
+        \ '**** Congress shall make no law'])
+  norm! 1gg
+  let expect = [
+	\ "* Congress shall    ",
+	\ "  make no law       ",
+	\ "*** Congress shall  ",
+	\ "    make no law     ",
+	\ "**** Congress shall ",
+	\ "     make no law    ",
+	\ ]
+  let lines = s:screen_lines2(1, 6, 20)
+  call s:compare_lines(expect, lines)
+
+  " check formatlistpat indent with different list level
+  " showbreak and sbr
+  setl briopt=min:5,sbr,list:-1,shift:2
+  setl showbreak=>
+  redraw!
+  let expect = [
+	\ "* Congress shall    ",
+	\ "> make no law       ",
+	\ "*** Congress shall  ",
+	\ ">   make no law     ",
+	\ "**** Congress shall ",
+	\ ">    make no law    ",
+	\ ]
+  let lines = s:screen_lines2(1, 6, 20)
+  call s:compare_lines(expect, lines)
+  call s:close_windows('set breakindent& briopt& linebreak& list& listchars& showbreak&')
 endfunc
 
 " vim: shiftwidth=2 sts=2 expandtab