[libxslt] Add test for issue #37

[Nick Wellnhofer <nwellnhof src gnome org>]

commit ea1c27fca299f4f29d8bd1e29ac2ad21aea81bcc
Author: Nick Wellnhofer <wellnhofer aevum de>
Date:   Wed Jun 24 16:10:45 2020 +0200

    Add test for issue #37
    
    This requires a recent version of libxml2 with commit libxml2@9f42f6ba.

 tests/exslt/common/node-set.9.out |  2 ++
 tests/exslt/common/node-set.9.xml |  4 ++++
 tests/exslt/common/node-set.9.xsl | 28 ++++++++++++++++++++++++++++
 3 files changed, 34 insertions(+)
---
diff --git a/tests/exslt/common/node-set.9.out b/tests/exslt/common/node-set.9.out
new file mode 100644
index 00000000..d75dd479
--- /dev/null
+++ b/tests/exslt/common/node-set.9.out
@@ -0,0 +1,2 @@
+<?xml version="1.0"?>
+<out><match/><match/></out>
diff --git a/tests/exslt/common/node-set.9.xml b/tests/exslt/common/node-set.9.xml
new file mode 100644
index 00000000..cf458854
--- /dev/null
+++ b/tests/exslt/common/node-set.9.xml
@@ -0,0 +1,4 @@
+<?xml version="1.0"?>
+
+<doc>
+</doc>
diff --git a/tests/exslt/common/node-set.9.xsl b/tests/exslt/common/node-set.9.xsl
new file mode 100644
index 00000000..bc76586f
--- /dev/null
+++ b/tests/exslt/common/node-set.9.xsl
@@ -0,0 +1,28 @@
+<?xml version="1.0"?>
+
+<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"; version="1.0"
+xmlns:exslt="http://exslt.org/common";
+extension-element-prefixes="exslt">
+
+<!-- https://gitlab.gnome.org/GNOME/libxslt/-/issues/37 -->
+
+<xsl:variable name="tree1">
+  <a><b><c><d/></c></b></a>
+</xsl:variable>
+<xsl:variable name="tree2">
+  <a><b><c><d/></c></b></a>
+</xsl:variable>
+
+<xsl:template match="a">
+  <xsl:for-each select="/*">
+    <match/>
+  </xsl:for-each>
+</xsl:template>
+
+<xsl:template match="/">
+  <out>
+    <xsl:apply-templates select="exslt:node-set($tree1)/a | exslt:node-set($tree2)/a"/>
+  </out>
+</xsl:template>
+
+</xsl:stylesheet>