vim-patch:8.2.3787: no proper formatting of a C line comment after a statement

Problem:    No proper formatting of a C line comment after a statement.
Solution:   Find the start of the line comment, insert the comment leader and
            indent the comment properly.
6e371ecb27

src/nvim/change.c

@@ -952,11 +952,13 @@ int copy_indent(int size, char_u *src)
 ///
 /// "second_line_indent": indent for after ^^D in Insert mode or if flag
 ///                       OPENLINE_COM_LIST
+/// "did_do_comment" is set to true when intentionally putting the comment
+/// leader in fromt of the new line.
 ///
 /// @param dir  FORWARD or BACKWARD
 ///
 /// @return true on success, false on failure
-int open_line(int dir, int flags, int second_line_indent)
+int open_line(int dir, int flags, int second_line_indent, bool *did_do_comment)
 {
   char_u *next_line = NULL;       // copy of the next line
   char_u *p_extra = NULL;         // what goes to next line
@@ -969,6 +971,7 @@ int open_line(int dir, int flags, int second_line_indent)
   bool retval = false;            // return value
   int extra_len = 0;              // length of p_extra string
   int lead_len;                   // length of comment leader
+  int comment_start = 0;          // start index of the comment leader
   char_u *lead_flags;             // position in 'comments' for comment leader
   char_u *leader = NULL;          // copy of comment leader
   char_u *allocated = NULL;       // allocated memory
@@ -977,6 +980,7 @@ int open_line(int dir, int flags, int second_line_indent)
   pos_T *pos;
   bool do_si = (!p_paste && curbuf->b_p_si && !curbuf->b_p_cin
                 && *curbuf->b_p_inde == NUL);
+  bool do_cindent;
   bool no_si = false;             // reset did_si afterwards
   int first_char = NUL;           // init for GCC
   int vreplace_mode;
@@ -1189,11 +1193,29 @@ int open_line(int dir, int flags, int second_line_indent)
     did_ai = true;
   }
 
+  // May do indenting after opening a new line.
+  do_cindent = !p_paste && (curbuf->b_p_cin || *curbuf->b_p_inde != NUL)
+               && in_cinkeys(dir == FORWARD ? KEY_OPEN_FORW : KEY_OPEN_BACK,
+                             ' ', linewhite(curwin->w_cursor.lnum));
+
   // Find out if the current line starts with a comment leader.
   // This may then be inserted in front of the new line.
   end_comment_pending = NUL;
   if (flags & OPENLINE_DO_COM) {
     lead_len = get_leader_len(saved_line, &lead_flags, dir == BACKWARD, true);
+    if (lead_len == 0 && do_cindent) {
+      comment_start = check_linecomment(saved_line);
+      if (comment_start != MAXCOL) {
+        lead_len = get_leader_len(saved_line + comment_start,
+                                  &lead_flags, dir == BACKWARD, true);
+        if (lead_len != 0) {
+          lead_len += comment_start;
+          if (did_do_comment != NULL) {
+            *did_do_comment = true;
+          }
+        }
+      }
+    }
   } else {
     lead_len = 0;
   }
@@ -1349,6 +1371,13 @@ int open_line(int dir, int flags, int second_line_indent)
 
       STRLCPY(leader, saved_line, lead_len + 1);
 
+      // TODO(vim): handle multi-byte and double width chars
+      for (int li = 0; li < comment_start; li++) {
+        if (!ascii_iswhite(leader[li])) {
+          leader[li] = ' ';
+        }
+      }
+
       // Replace leader with lead_repl, right or left adjusted
       if (lead_repl != NULL) {
         int c = 0;
@@ -1758,13 +1787,7 @@ int open_line(int dir, int flags, int second_line_indent)
     ai_col = (colnr_T)getwhitecols_curline();
   }
   // May do indenting after opening a new line.
-  if (!p_paste
-      && (curbuf->b_p_cin
-          || *curbuf->b_p_inde != NUL
-          )
-      && in_cinkeys(dir == FORWARD
-                    ? KEY_OPEN_FORW
-                    : KEY_OPEN_BACK, ' ', linewhite(curwin->w_cursor.lnum))) {
+  if (do_cindent) {
     do_c_expr_indent();
     ai_col = (colnr_T)getwhitecols_curline();
   }

src/nvim/edit.c

@@ -6021,6 +6021,7 @@ static void internal_format(int textwidth, int second_indent, int flags, int for
     char_u *saved_text = NULL;
     colnr_T col;
     colnr_T end_col;
+    bool did_do_comment = false;
 
     virtcol = get_nolist_virtcol()
               + char2cells(c != NUL ? c : gchar_cursor());
@@ -6294,11 +6295,18 @@ static void internal_format(int textwidth, int second_indent, int flags, int for
               + (fo_white_par ? OPENLINE_KEEPTRAIL : 0)
               + (do_comments ? OPENLINE_DO_COM : 0)
               + ((flags & INSCHAR_COM_LIST) ? OPENLINE_COM_LIST : 0),
-              ((flags & INSCHAR_COM_LIST) ? second_indent : old_indent));
+              ((flags & INSCHAR_COM_LIST) ? second_indent : old_indent),
+              &did_do_comment);
     if (!(flags & INSCHAR_COM_LIST)) {
       old_indent = 0;
     }
 
+    // If a comment leader was inserted, may also do this on a following
+    // line.
+    if (did_do_comment) {
+      no_leader = false;
+    }
+
     replace_offset = 0;
     if (first_line) {
       if (!(flags & INSCHAR_COM_LIST)) {
@@ -9183,7 +9191,7 @@ static bool ins_eol(int c)
   AppendToRedobuff(NL_STR);
   bool i = open_line(FORWARD,
                      has_format_option(FO_RET_COMS) ? OPENLINE_DO_COM : 0,
-                     old_indent);
+                     old_indent, NULL);
   old_indent = 0;
   can_cindent = true;
   // When inserting a line the cursor line must never be in a closed fold.

src/nvim/indent_c.c

@@ -1906,13 +1906,26 @@ int get_c_indent(void)
    * If we're inside a "//" comment and there is a "//" comment in a
    * previous line, lineup with that one.
    */
-  if (cin_islinecomment(theline)
-      && (trypos = find_line_comment()) != NULL) {  // XXX
+  if (cin_islinecomment(theline)) {
+    pos_T linecomment_pos;
+
+    trypos = find_line_comment();  // XXX
+    if (trypos == NULL && curwin->w_cursor.lnum > 1) {
+      // There may be a statement before the comment, search from the end
+      // of the line for a comment start.
+      linecomment_pos.col = check_linecomment(ml_get(curwin->w_cursor.lnum - 1));
+      if (linecomment_pos.col != MAXCOL) {
+        trypos = &linecomment_pos;
+        trypos->lnum = curwin->w_cursor.lnum - 1;
+      }
+    }
+    if (trypos != NULL) {
       // find how indented the line beginning the comment is
       getvcol(curwin, trypos, &col, NULL, NULL);
       amount = col;
       goto theend;
     }
+  }
   /*
    * If we're inside a comment and not looking at the start of the
    * comment, try using the 'comments' option.

src/nvim/normal.c

@@ -6685,9 +6685,8 @@ static void n_opencmd(cmdarg_T *cap)
                           (cap->cmdchar == 'o' ? 1 : 0))
                )
         && open_line(cap->cmdchar == 'O' ? BACKWARD : FORWARD,
-                     has_format_option(FO_OPEN_COMS)
-                     ? OPENLINE_DO_COM : 0,
-                     0)) {
+                     has_format_option(FO_OPEN_COMS) ? OPENLINE_DO_COM : 0,
+                     0, NULL)) {
       if (win_cursorline_standout(curwin)) {
         // force redraw of cursorline
         curwin->w_valid &= ~VALID_CROW;

src/nvim/search.c

@@ -2318,7 +2318,7 @@ pos_T *findmatchlimit(oparg_T *oap, int initc, int flags, int64_t maxtravel)
  * Return MAXCOL if not, otherwise return the column.
  * TODO: skip strings.
  */
-static int check_linecomment(const char_u *line)
+int check_linecomment(const char_u *line)
 {
   const char_u *p = line;  // scan from start
   // skip Lispish one-line comments

src/nvim/testdir/test_textformat.vim

@@ -196,6 +196,36 @@ func Test_text_format()
   enew!
 endfunc
 
+func Test_format_c_comment()
+  new
+  setl ai cindent tw=40 et fo=croql
+  let text =<< trim END
+      var = 2345;  // asdf asdf asdf asdf asdf asdf asdf asdf asdf asdf
+  END
+  call setline(1, text)
+  normal gql
+  let expected =<< trim END
+      var = 2345;  // asdf asdf asdf asdf asdf
+                   // asdf asdf asdf asdf asdf
+  END
+  call assert_equal(expected, getline(1, '$'))
+
+  %del
+  let text =<< trim END
+      var = 2345;  // asdf asdf asdf asdf asdf asdf asdf asdf asdf asdf asdf asdf
+  END
+  call setline(1, text)
+  normal gql
+  let expected =<< trim END
+      var = 2345;  // asdf asdf asdf asdf asdf
+                   // asdf asdf asdf asdf asdf
+                   // asdf asdf
+  END
+  call assert_equal(expected, getline(1, '$'))
+
+  bwipe!
+endfunc
+
 " Tests for :right, :center and :left on text with embedded TAB.
 func Test_format_align()
   enew!