From a523088e937ba170e198c1080112d6bfab51a27c Mon Sep 17 00:00:00 2001
From: Ingo Schwarze <schwarze@openbsd.org>
Date: Fri, 19 Jul 2019 20:27:25 +0000
Subject: If no tags were generated at all, unlink(2) the empty tags file as
 soon as the condition can be detected and do not pass it to less(1). This may
 happen for man(7) pages, for preformatted pages, and for very simple pages
 like true(1).  The main benefit is that :t inside less(1) yields the clearer
 diagnostic message "No tags file" rather than the mildly confusing "No such
 tag in tags file": the latter might encourage further, futile attempts to
 jump to other tags.

Improvement suggested by Leah Neukirchen <leah at vuxu dot org>
from The Void.
---
 main.c |  2 +-
 tag.c  | 13 +++++++++++--
 2 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/main.c b/main.c
index e5a3976b..307e65dc 100644
--- a/main.c
+++ b/main.c
@@ -1194,7 +1194,7 @@ spawn_pager(struct tag_files *tag_files)
 
 	use_ofn = 1;
 #if HAVE_LESS_T
-	if ((cmdlen = strlen(argv[0])) >= 4) {
+	if (*tag_files->tfn != '\0' && (cmdlen = strlen(argv[0])) >= 4) {
 		cp = argv[0] + cmdlen - 4;
 		if (strcmp(cp, "less") == 0) {
 			argv[argc++] = mandoc_strdup("-T");
diff --git a/tag.c b/tag.c
index a0b0cd35..edff5064 100644
--- a/tag.c
+++ b/tag.c
@@ -225,6 +225,7 @@ tag_write(void)
 	struct tag_entry	*entry;
 	size_t			 i;
 	unsigned int		 slot;
+	int			 empty;
 
 	if (tag_files.tfd <= 0)
 		return;
@@ -235,12 +236,16 @@ tag_write(void)
 	}
 	if ((stream = fdopen(tag_files.tfd, "w")) == NULL)
 		mandoc_msg(MANDOCERR_FDOPEN, 0, 0, "%s", strerror(errno));
+	empty = 1;
 	entry = ohash_first(&tag_data, &slot);
 	while (entry != NULL) {
-		if (stream != NULL && entry->prio >= 0)
-			for (i = 0; i < entry->nlines; i++)
+		if (stream != NULL && entry->prio >= 0) {
+			for (i = 0; i < entry->nlines; i++) {
 				fprintf(stream, "%s %s %zu\n",
 				    entry->s, tag_files.ofn, entry->lines[i]);
+				empty = 0;
+			}
+		}
 		free(entry->lines);
 		free(entry);
 		entry = ohash_next(&tag_data, &slot);
@@ -251,6 +256,10 @@ tag_write(void)
 	else
 		close(tag_files.tfd);
 	tag_files.tfd = -1;
+	if (empty) {
+		unlink(tag_files.tfn);
+		*tag_files.tfn = '\0';
+	}
 }
 
 void
-- 
cgit