From: Omar Polo <op@omarpolo.com>
Subject: Re: mg: "support" for exuberant/universal ctags tags files
To: Omar Polo <op@omarpolo.com>
Cc: tech@openbsd.org
Date: Tue, 04 Jun 2024 08:59:56 +0200

36-week bump :)

I noticed I still had this in my tree.  Actually I am in doubt whether
to actually keep the first hunk or not, I could as well drop it, but the
others are nice for compatibility.

While it could be interesting to support uctags annotations, I don't
have plans to do so.

Thoughts?

On 2023/09/27 18:23:52 +0200, Omar Polo <op@omarpolo.com> wrote:
> TL;DR "support" because this is not about supporting the fancy new
> stuff, but just not breaking on a universal-ctags generated tag file.
> I'd just like to tell mg enough of the file format to ignore the
> extensions over plain tag files.
> 
> The diff is mostly from troglobit' mg:
> https://github.com/troglobit/mg/commit/64cd07ecf5c521d50966eca8ba04026e7c9f3be8
> 
> The documentation about the universal-ctags extension over tags files
> is documented in utags(5) after you install the universal-ctags
> package.  Tags file entries follows this scheme:
> 
> 	{tagname}<tab>{tagfile}<tab>{tagaddress}
> 
> where tagaddress is an ex command (could be anything, I haven't
> checked how vi(1) actually implements it, but mg assumes it's a search
> and just does that.  Works most of the times).
> 
> To store extra metadata about the tag itself, the address is put a
> comment in the tagaddress.  For example, here's how the main() entry
> would look like.  Not the type information after ;"
> 
> % uctags *.c
> % g ^main tags
> tags:526: main  main.c  /^main(int argc, char **argv)$/;"       f       typeref:typename:int
> 
> Similarly, universal-ctags introduced support for some meta-tag using
> some dummy entries under the !_TAG_ "namespace"
> (e.g. !_TAG_FILE_FORMAT, !_TAG_FILE_SORTED, ...)
> 
> So, the idea is to just ignore tags starting with !_TAG_ and ignore
> comments.  As simple as that :-)

Index: tags.c
===================================================================
RCS file: /home/cvs/src/usr.bin/mg/tags.c,v
diff -u -p -r1.27 tags.c
--- tags.c	29 Mar 2023 19:09:04 -0000	1.27
+++ tags.c	27 Sep 2023 16:21:42 -0000
@@ -281,6 +281,10 @@ loadtags(const char *fn)
 	}
 	while ((l = fparseln(fd, NULL, NULL, "\\\\\0",
 	    FPARSELN_UNESCCONT | FPARSELN_UNESCREST)) != NULL) {
+		if (!strncmp(l, "!_TAG_", 6)) {
+			free(l);
+			continue;
+		}
 		if (addctag(l) == FALSE) {
 			fclose(fd);
 			return (FALSE);
@@ -340,7 +344,7 @@ int
 addctag(char *s)
 {
 	struct ctag *t = NULL;
-	char *l;
+	char *l, *c;
 
 	if ((t = malloc(sizeof(struct ctag))) == NULL) {
 		dobeep();
@@ -357,6 +361,15 @@ addctag(char *s)
 	*l++ = '\0';
 	if (*l == '\0')
 		goto cleanup;
+
+	/*
+	 * Newer universal ctags format abuse vi comments in the
+	 * pattern to store extra metadata.  Since we don't support it
+	 * remove it so the pattern is not mangled.
+	 */
+	if ((c = strstr(l, ";\"")) != NULL)
+		*c = '\0';
+
 	t->pat = strip(l, strlen(l));
 	if (RB_INSERT(tagtree, &tags, t) != NULL) {
 		free(t);