vim-patch:8.1.0728: avoid breaking after single space #9733

Problem:    Cannot avoid breaking after a single space.
Solution:   Add the 'p' flag to 'formatoptions'. (Tom Ryder)
c3c3158756

runtime/doc/change.txt

@@ -1635,6 +1635,17 @@ j	Where it makes sense, remove a comment leader when joining lines.  For
 		         // in the list ~
 	Becomes:
 		int i;   // the index in the list ~
+p	Don't break lines at single spaces that follow periods.  This is
+	intended to complement 'joinspaces' and |cpo-J|, for prose with
+	sentences separated by two spaces.  For example, with 'textwidth' set
+	to 28: >
+		Surely you're joking, Mr. Feynman!
+<	Becomes: >
+		Surely you're joking,
+		Mr. Feynman!
+<	Instead of: >
+		Surely you're joking, Mr.
+		Feynman!
 
 
 With 't' and 'c' you can specify when Vim performs auto-wrapping:

src/nvim/edit.c

@@ -5486,16 +5486,33 @@ internal_format (
         /* remember position of blank just before text */
         end_col = curwin->w_cursor.col;
 
-        /* find start of sequence of blanks */
+        // find start of sequence of blanks
+        int wcc = 0;  // counter for whitespace chars
         while (curwin->w_cursor.col > 0 && WHITECHAR(cc)) {
           dec_cursor();
           cc = gchar_cursor();
+
+          // Increment count of how many whitespace chars in this
+          // group; we only need to know if it's more than one.
+          if (wcc < 2) {
+            wcc++;
           }
-        if (curwin->w_cursor.col == 0 && WHITECHAR(cc))
-          break;                        /* only spaces in front of text */
-        /* Don't break until after the comment leader */
-        if (curwin->w_cursor.col < leader_len)
+        }
+        if (curwin->w_cursor.col == 0 && WHITECHAR(cc)) {
+          break;                        // only spaces in front of text
+        }
+
+        // Don't break after a period when 'formatoptions' has 'p' and
+        // there are less than two spaces.
+        if (has_format_option(FO_PERIOD_ABBR) && cc == '.' && wcc < 2) {
+          continue;
+        }
+
+        // Don't break until after the comment leader
+        if (curwin->w_cursor.col < leader_len) {
           break;
+        }
+
         if (has_format_option(FO_ONE_LETTER)) {
           /* do not break after one-letter words */
           if (curwin->w_cursor.col == 0)

src/nvim/option_defs.h

@@ -74,13 +74,14 @@
 #define FO_MBYTE_JOIN   'M'     /* no space before/after multi-byte char */
 #define FO_MBYTE_JOIN2  'B'     /* no space between multi-byte chars */
 #define FO_ONE_LETTER   '1'
-#define FO_WHITE_PAR    'w'     /* trailing white space continues paragr. */
-#define FO_AUTO         'a'     /* automatic formatting */
-#define FO_REMOVE_COMS  'j'     /* remove comment leaders when joining lines */
+#define FO_WHITE_PAR    'w'     // trailing white space continues paragr.
+#define FO_AUTO         'a'     // automatic formatting
+#define FO_REMOVE_COMS  'j'     // remove comment leaders when joining lines
+#define FO_PERIOD_ABBR  'p'     // don't break a single space after a period
 
 #define DFLT_FO_VI      "vt"
 #define DFLT_FO_VIM     "tcqj"
-#define FO_ALL          "tcroq2vlb1mMBn,awj"    /* for do_set() */
+#define FO_ALL          "tcroq2vlb1mMBn,awjp"   // for do_set()
 
 // characters for the p_cpo option:
 #define CPO_ALTREAD     'a'     // ":read" sets alternate file name

src/nvim/testdir/test_textformat.vim

@@ -163,6 +163,32 @@ func Test_text_format()
 	      \ '# 1 xxxxx',
 	      \ '#   foobar'], getline(1, 2))
 
+  " Test the 'p' flag for 'formatoptions'
+  " First test without the flag: that it will break "Mr. Feynman" at the space
+  normal ggdG
+  setl tw=28 fo=tcq
+  call setline('.', 'Surely you''re joking, Mr. Feynman!')
+  normal gqq
+  call assert_equal([
+              \ 'Surely you''re joking, Mr.',
+              \ 'Feynman!'], getline(1, 2))
+  " Now test with the flag: that it will push the name with the title onto the
+  " next line
+  normal ggdG
+  setl fo+=p
+  call setline('.', 'Surely you''re joking, Mr. Feynman!')
+  normal gqq
+  call assert_equal([
+              \ 'Surely you''re joking,',
+              \ 'Mr. Feynman!'], getline(1, 2))
+  " Ensure that it will still break if two spaces are entered
+  normal ggdG
+  call setline('.', 'Surely you''re joking, Mr.  Feynman!')
+  normal gqq
+  call assert_equal([
+              \ 'Surely you''re joking, Mr.',
+              \ 'Feynman!'], getline(1, 2))
+
   setl ai& tw& fo& si& comments&
   enew!
 endfunc