From ff230b2956aafd42161f203fabde7ce05ea4d8c0 Mon Sep 17 00:00:00 2001
From: Mike Frysinger <vapier@gentoo.org>
Date: Thu, 24 Feb 2022 22:25:45 -0500
Subject: automake: fall back gracefully when texinfo inputs don't exist

Fixes automake bug https://bugs.gnu.org/54063.

The function scanning for @setfilename will fall back to a default
value if the input doesn't have one defined.  But we need to handle
the case where the file doesn't even exist before falling back.

* bin/automake.in: Scan /dev/null for @setfilename if input doesn't exist.
* t/list-of-tests.mk: Add txinfo-no-setfilename-no-inputs.sh.
* t/txinfo-no-setfilename-no-inputs.sh: New test.
---
 bin/automake.in                      |  4 +++-
 t/list-of-tests.mk                   |  1 +
 t/txinfo-no-setfilename-no-inputs.sh | 31 +++++++++++++++++++++++++++++++
 3 files changed, 35 insertions(+), 1 deletion(-)
 create mode 100644 t/txinfo-no-setfilename-no-inputs.sh

diff --git a/bin/automake.in b/bin/automake.in
index 9747510f9..c094234bc 100644
--- a/bin/automake.in
+++ b/bin/automake.in
@@ -3062,7 +3062,9 @@ sub scan_texinfo_file
 {
   my ($filename) = @_;
 
-  my $texi = new Automake::XFile "< $filename";
+  # If the source file doesn't exist, we'll fall back below.
+  my $source = -e $filename ? $filename : "/dev/null";
+  my $texi = new Automake::XFile "< $source";
   verb "reading $filename";
 
   my ($outfile, $vfile);
diff --git a/t/list-of-tests.mk b/t/list-of-tests.mk
index dbfd8d6d1..0af117a5a 100644
--- a/t/list-of-tests.mk
+++ b/t/list-of-tests.mk
@@ -1230,6 +1230,7 @@ t/txinfo-no-extra-dist.sh \
 t/txinfo-no-installinfo.sh \
 t/txinfo-no-repeated-targets.sh \
 t/txinfo-no-setfilename.sh \
+t/txinfo-no-setfilename-no-inputs.sh \
 t/txinfo-other-suffixes.sh \
 t/txinfo-override-infodeps.sh \
 t/txinfo-override-texinfo-tex.sh \
diff --git a/t/txinfo-no-setfilename-no-inputs.sh b/t/txinfo-no-setfilename-no-inputs.sh
new file mode 100644
index 000000000..4cedb2f88
--- /dev/null
+++ b/t/txinfo-no-setfilename-no-inputs.sh
@@ -0,0 +1,31 @@
+#! /bin/sh
+# Copyright (C) 2022 Free Software Foundation, Inc.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2, or (at your option)
+# any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+# Check Texinfo files work without a @setfilename line and no input files.
+# https://bugs.gnu.org/54063
+
+. test-init.sh
+
+cat > Makefile.am << 'END'
+info_TEXINFOS = file.texi
+END
+
+$ACLOCAL
+$AUTOMAKE --add-missing
+
+grep 'file.info:' Makefile.in
+
+:
-- 
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