mandoc: If a node is tagged explicitly, skip implicit tagging for that

mandoc: If a node is tagged explicitly, skip implicit tagging for that

[schwarze]

Log Message:
-----------
If a node is tagged explicitly, skip implicit tagging for that node.
Apart from making sense in the first place, this fixes an assertion
failure that happened when the calculated implicit tag did not match
the string value of the first child of the node,

Bug found by tb@ using afl(1).

Modified Files:
--------------
    mandoc:
        tag.c
    mandoc/regress/mdoc/Tg:
        Makefile

Added Files:
-----------
    mandoc/regress/mdoc/Tg:
        implicit.in
        implicit.out_ascii
        implicit.out_html
        implicit.out_markdown
        implicit.out_tag

Revision Data
-------------
Index: tag.c
===================================================================
RCS file: /home/cvs/mandoc/mandoc/tag.c,v
retrieving revision 1.36
retrieving revision 1.37
diff -Ltag.c -Ltag.c -u -p -r1.36 -r1.37
--- tag.c
+++ tag.c
@@ -1,6 +1,7 @@
 /* $Id$ */
 /*
- * Copyright (c) 2015,2016,2018,2019,2020 Ingo Schwarze <schwarze@openbsd.org>
+ * Copyright (c) 2015, 2016, 2018, 2019, 2020, 2022
+ *               Ingo Schwarze <schwarze@openbsd.org>
  *
  * Permission to use, copy, modify, and distribute this software for any
  * purpose with or without fee is hereby granted, provided that the above
@@ -80,7 +81,7 @@ tag_free(void)
 
 /*
  * Set a node where a term is defined,
- * unless it is already defined at a lower priority.
+ * unless the term is already defined at a lower priority.
  */
 void
 tag_put(const char *s, int prio, struct roff_node *n)
@@ -93,6 +94,18 @@ tag_put(const char *s, int prio, struct 
 
 	assert(prio <= TAG_FALLBACK);
 
+	/*
+	 * If the node is already tagged, the existing tag is
+	 * explicit and we are now about to add an implicit tag.
+	 * Don't do that; just skip implicit tagging if the author
+	 * specified an explicit tag.
+	 */
+
+	if (n->flags & NODE_ID)
+		return;
+
+	/* Determine the implicit tag. */
+
 	if (s == NULL) {
 		if (n->child == NULL || n->child->type != ROFFT_TEXT)
 			return;
@@ -150,7 +163,7 @@ tag_put(const char *s, int prio, struct 
 	 */
 
 	else if (entry->prio < prio)
-			return;
+		return;
 
 	/*
 	 * If the existing entry is worse, clear it.
--- /dev/null
+++ regress/mdoc/Tg/implicit.out_tag
@@ -0,0 +1,3 @@
+NAME implicit.mandoc_ascii 3
+DESCRIPTION implicit.mandoc_ascii 6
+explicit implicit.mandoc_ascii 9
--- /dev/null
+++ regress/mdoc/Tg/implicit.out_ascii
@@ -0,0 +1,13 @@
+TG-IMPLICIT(1)              General Commands Manual             TG-IMPLICIT(1)
+
+N\bNA\bAM\bME\bE
+     T\bTg\bg-\b-i\bim\bmp\bpl\bli\bic\bci\bit\bt - overriding implicit tagging
+
+D\bDE\bES\bSC\bCR\bRI\bIP\bPT\bTI\bIO\bON\bN
+     BEGINTEST
+
+     i\bim\bmp\bpl\bli\bic\bci\bit\bt i\bis\bs u\bun\bns\bsu\bus\bse\bed\bd
+
+     ENDTEST
+
+OpenBSD                         April 26, 2022                         OpenBSD
--- /dev/null
+++ regress/mdoc/Tg/implicit.out_html
@@ -0,0 +1,2 @@
+<p class="Pp" id="explicit"><a class="permalink" href="#explicit"><b class="Sy">implicit
+    is unsused</b></a></p>
Index: Makefile
===================================================================
RCS file: /home/cvs/mandoc/mandoc/regress/mdoc/Tg/Makefile,v
retrieving revision 1.2
retrieving revision 1.3
diff -Lregress/mdoc/Tg/Makefile -Lregress/mdoc/Tg/Makefile -u -p -r1.2 -r1.3
--- regress/mdoc/Tg/Makefile
+++ regress/mdoc/Tg/Makefile
@@ -1,9 +1,9 @@
-# $OpenBSD: Makefile,v 1.2 2020/04/06 09:55:50 schwarze Exp $
+# $OpenBSD: Makefile,v 1.3 2022/04/26 11:28:35 schwarze Exp $
 
-REGRESS_TARGETS = column list warn
-TAG_TARGETS	= column list warn
+REGRESS_TARGETS = column implicit list warn
+TAG_TARGETS	= column implicit list warn
 LINT_TARGETS	= warn
-HTML_TARGETS	= column list warn
+HTML_TARGETS	= column implicit list warn
 
 SKIP_TMAN	= column
 
--- /dev/null
+++ regress/mdoc/Tg/implicit.out_markdown
@@ -0,0 +1,15 @@
+TG-IMPLICIT(1) - General Commands Manual
+
+# NAME
+
+**Tg-implicit** - overriding implicit tagging
+
+# DESCRIPTION
+
+BEGINTEST
+
+**implicit is unsused**
+
+ENDTEST
+
+OpenBSD - April 26, 2022
--- /dev/null
+++ regress/mdoc/Tg/implicit.in
@@ -0,0 +1,14 @@
+.\" $OpenBSD: implicit.in,v 1.1 2022/04/26 11:28:35 schwarze Exp $
+.Dd $Mdocdate: April 26 2022 $
+.Dt TG-IMPLICIT 1
+.Os
+.Sh NAME
+.Nm Tg-implicit
+.Nd overriding implicit tagging
+.Sh DESCRIPTION
+BEGINTEST
+.Pp
+.Tg explicit
+.Sy implicit is unsused
+.Pp
+ENDTEST
--
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