patch 9.2.0506: home_replace() function can be improved

Problem:  home_replace() function can be improved
Solution: Refactor home_replace() to return the length of the string
          (John Marriott).

In addition:
- in function set_b0_fname() move ulen into the block where it is used.
- In function findswapname() rework logic around displaying "swap file
  already exists" dialogue so that literal message text is set once.

closes: #20249

Signed-off-by: John Marriott <basilisk@internode.on.net>
Signed-off-by: Christian Brabandt <cb@256bit.org>

src/buffer.c

@@ -3948,9 +3948,8 @@ fileinfo(
 	    name = curbuf->b_fname;
 	else
 	    name = curbuf->b_ffname;
-	home_replace(shorthelp ? curbuf : NULL, name, (char_u *)buffer + bufferlen,
-					  IOSIZE - (int)bufferlen, TRUE);
-	bufferlen += STRLEN(buffer + bufferlen);
+	bufferlen += home_replace(shorthelp ? curbuf : NULL, name,
+	    (char_u *)buffer + bufferlen, IOSIZE - (int)bufferlen, TRUE);
     }
 
     bufferlen += vim_snprintf_safelen(

src/fileio.c

@@ -3200,11 +3200,13 @@ set_rw_fname(char_u *fname, char_u *sfname)
     void
 msg_add_fname(buf_T *buf, char_u *fname)
 {
+    size_t  IObufflen = 0;
+
     if (fname == NULL)
 	fname = (char_u *)"-stdin-";
-    home_replace(buf, fname, IObuff + 1, IOSIZE - 4, TRUE);
-    IObuff[0] = '"';
-    STRCAT(IObuff, "\" ");
+    IObuff[IObufflen++] = '"';
+    IObufflen += home_replace(buf, fname, IObuff + IObufflen, IOSIZE - 4, TRUE);
+    STRCPY(IObuff + IObufflen, "\" ");
 }
 
 /*

src/filepath.c

@@ -442,27 +442,29 @@ repeat:
 
 	if (p != NULL)
 	{
+	    size_t  dirnamelen = 0;
+
 	    if (c == '.')
 	    {
-		size_t	namelen;
-
 		mch_dirname(dirname, MAXPATHL);
 		if (has_homerelative)
 		{
 		    s = vim_strsave(dirname);
 		    if (s != NULL)
 		    {
-			home_replace(NULL, s, dirname, MAXPATHL, TRUE);
+			dirnamelen = home_replace(NULL, s, dirname, MAXPATHL, TRUE);
 			vim_free(s);
 		    }
 		}
-		namelen = STRLEN(dirname);
+
+		if (dirnamelen == 0)
+		    dirnamelen = STRLEN(dirname);
 
 		// Do not call shorten_fname() here since it removes the prefix
 		// even though the path does not have a prefix.
-		if (fnamencmp(p, dirname, namelen) == 0)
+		if (fnamencmp(p, dirname, dirnamelen) == 0)
 		{
-		    p += namelen;
+		    p += dirnamelen;
 		    if (vim_ispathsep(*p))
 		    {
 			while (*p && vim_ispathsep(*p))
@@ -480,11 +482,11 @@ repeat:
 	    }
 	    else
 	    {
-		home_replace(NULL, p, dirname, MAXPATHL, TRUE);
+		dirnamelen = home_replace(NULL, p, dirname, MAXPATHL, TRUE);
 		// Only replace it when it starts with '~'
 		if (*dirname == '~')
 		{
-		    s = vim_strsave(dirname);
+		    s = vim_strnsave(dirname, dirnamelen);
 		    if (s != NULL)
 		    {
 			*fnamep = s;
@@ -2724,7 +2726,7 @@ f_filecopy(typval_T *argvars, typval_T *rettv)
  * 'src'.
  * If anything fails (except when out of space) dst equals src.
  */
-    void
+    size_t
 home_replace(
     buf_T	*buf,	// when not NULL, check for help files
     char_u	*src,	// input file name
@@ -2737,21 +2739,19 @@ home_replace(
     size_t	len;
     char_u	*homedir_env, *homedir_env_orig;
     char_u	*p;
+    char_u	*dst_start;
 
     if (src == NULL)
     {
 	*dst = NUL;
-	return;
+	return 0;
     }
 
     /*
      * If the file is a help file, remove the path completely.
      */
     if (buf != NULL && buf->b_help)
-    {
-	vim_snprintf((char *)dst, dstlen, "%s", gettail(src));
-	return;
-    }
+	return vim_snprintf_safelen((char *)dst, dstlen, "%s", gettail(src));
 
     /*
      * We check both the value of the $HOME environment variable and the
@@ -2793,6 +2793,7 @@ home_replace(
 
     if (!one)
 	src = skipwhite(src);
+    dst_start = dst;		// remember the start
     while (*src && dstlen > 0)
     {
 	/*
@@ -2842,6 +2843,8 @@ home_replace(
 
     if (homedir_env != homedir_env_orig)
 	vim_free(homedir_env);
+
+    return (size_t)(dst - dst_start);
 }
 
 /*

src/memline.c

@@ -1021,7 +1021,7 @@ set_b0_fname(ZERO_BL *b0p, buf_T *buf)
 	forward_slash(b0p->b0_fname);
 # endif
 #else
-	size_t	flen, ulen;
+	size_t	flen;
 	char_u	uname[B0_UNAME_SIZE];
 
 	/*
@@ -1031,11 +1031,12 @@ set_b0_fname(ZERO_BL *b0p, buf_T *buf)
 	 * First replace home dir path with "~/" with home_replace().
 	 * Then insert the user name to get "~user/".
 	 */
-	home_replace(NULL, buf->b_ffname, b0p->b0_fname,
+	flen = home_replace(NULL, buf->b_ffname, b0p->b0_fname,
 						   B0_FNAME_SIZE_CRYPT, TRUE);
 	if (b0p->b0_fname[0] == '~')
 	{
-	    flen = STRLEN(b0p->b0_fname);
+	    size_t  ulen;
+
 	    // If there is no user name or it is too long, don't use "~/"
 	    if (get_user_name(uname, B0_UNAME_SIZE) == FAIL
 		   || (ulen = STRLEN(uname)) + flen > B0_FNAME_SIZE_CRYPT - 1)
@@ -5343,24 +5344,32 @@ findswapname(
 		    if (swap_exists_action != SEA_NONE
 						  && choice == SEA_CHOICE_NONE)
 		    {
-			char_u	*name;
-			int	dialog_result;
-			size_t  len = STRLEN(_("Swap file \""));
+			string_T    prefix = {(char_u *)_("Swap file \""), 0};
+			string_T    suffix = {(char_u *)_("\" already exists!"), 0};
+			size_t	    message_size;
+			string_T    message;
+			char_u	    *tofree;
+			int	    dialog_result;
 
-			name = alloc(STRLEN(fname)
-				+ len
-				+ STRLEN(_("\" already exists!")) + 5);
-			if (name != NULL)
+			prefix.length = STRLEN(prefix.string);
+			suffix.length = STRLEN(suffix.string);
+			message_size = prefix.length
+				+ STRLEN(fname)
+				+ suffix.length + 5;
+			message.string = tofree = alloc(message_size);
+			if (message.string != NULL)
 			{
-			    STRCPY(name, _("Swap file \""));
-			    home_replace(NULL, fname, name + len, 1000, TRUE);
-			    STRCAT(name, _("\" already exists!"));
+			    STRCPY(message.string, prefix.string);
+			    message.length = prefix.length;
+			    message.length += home_replace(NULL, fname,
+				message.string + message.length, (int)(message_size - message.length), TRUE);
+			    STRCPY(message.string + message.length, suffix.string);
 			}
+			else
+			    message.string = (char_u *)_("Swap file already exists!");
 			dialog_result = do_dialog(VIM_WARNING,
 				    (char_u *)_("VIM - ATTENTION"),
-				    name == NULL
-					?  (char_u *)_("Swap file already exists!")
-					: name,
+				    message.string,
 # ifdef HAVE_PROCESS_STILL_RUNNING
 				    process_still_running
 					? (char_u *)_("&Open Read-Only\n&Edit anyway\n&Recover\n&Quit\n&Abort") :
@@ -5373,7 +5382,7 @@ findswapname(
 			    dialog_result++;
 # endif
 			choice = dialog_result;
-			vim_free(name);
+			vim_free(tofree);
 
 			// pretend screen didn't scroll, need redraw anyway
 			msg_scrolled = 0;

src/po/vim.pot

@@ -8,7 +8,7 @@ msgid ""
 msgstr ""
 "Project-Id-Version: Vim\n"
 "Report-Msgid-Bugs-To: vim-dev@vim.org\n"
-"POT-Creation-Date: 2026-05-19 18:20+0000\n"
+"POT-Creation-Date: 2026-05-20 18:41+0000\n"
 "PO-Revision-Date: YEAR-MO-DA HO:MI+ZONE\n"
 "Last-Translator: FULL NAME <EMAIL@ADDRESS>\n"
 "Language-Team: LANGUAGE <LL@li.org>\n"
@@ -2169,10 +2169,10 @@ msgstr ""
 msgid "\" already exists!"
 msgstr ""
 
-msgid "VIM - ATTENTION"
+msgid "Swap file already exists!"
 msgstr ""
 
-msgid "Swap file already exists!"
+msgid "VIM - ATTENTION"
 msgstr ""
 
 msgid ""

src/proto/filepath.pro

@@ -36,7 +36,7 @@ char_u *do_browse(int flags, char_u *title, char_u *dflt, char_u *ext, char_u *i
 void f_browse(typval_T *argvars, typval_T *rettv);
 void f_browsedir(typval_T *argvars, typval_T *rettv);
 void f_filecopy(typval_T *argvars, typval_T *rettv);
-void home_replace(buf_T *buf, char_u *src, char_u *dst, int dstlen, int one);
+size_t home_replace(buf_T *buf, char_u *src, char_u *dst, int dstlen, int one);
 char_u *home_replace_save(buf_T *buf, char_u *src);
 int fullpathcmp(char_u *s1, char_u *s2, int checkname, int expandenv);
 char_u *gettail(char_u *fname);

src/version.c

@@ -729,6 +729,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    506,
 /**/
     505,
 /**/

src/viminfo.c

@@ -435,6 +435,8 @@ write_viminfo_bufferlist(FILE *fp)
     fputs(_("\n# Buffer list:\n"), fp);
     FOR_ALL_BUFFERS(buf)
     {
+	size_t	linelen;
+
 	if (buf->b_fname == NULL
 		|| !buf->b_p_bl
 		|| bt_quickfix(buf)
@@ -445,8 +447,8 @@ write_viminfo_bufferlist(FILE *fp)
 	if (max_buffers-- == 0)
 	    break;
 	putc('%', fp);
-	home_replace(NULL, buf->b_ffname, line, MAXPATHL, TRUE);
-	vim_snprintf_add((char *)line, LINE_BUF_LEN, "\t%ld\t%d",
+	linelen = home_replace(NULL, buf->b_ffname, line, MAXPATHL, TRUE);
+	vim_snprintf((char *)line + linelen, LINE_BUF_LEN - linelen, "\t%ld\t%d",
 			(long)buf->b_last_cursor.lnum,
 			buf->b_last_cursor.col);
 	viminfo_writestring(fp, line);