Fix contrib/xml2 so regression test still works when it's built without libxslt.

This involves modifying the module to have a stable ABI, that is, the
xslt_process() function still exists even without libxslt.  It throws a
runtime error if called, but doesn't prevent executing the CREATE FUNCTION
call.  This is a good thing anyway to simplify cross-version upgrades.

contrib/xml2/Makefile

@@ -1,20 +1,28 @@
 # This makefile will build the new XML and XSLT routines.
 
+# This module will not work without libxml2, but it will work without libxslt.
+# To build without libxslt, run "gmake USE_LIBXSLT=0", or comment out the
+# following line:
+USE_LIBXSLT = 1
+
 MODULE_big = pgxml
 
-# Remove xslt_proc.o from the following line if you don't have libxslt
 OBJS = xpath.o xslt_proc.o
 
-# Remove -lxslt from the following line if you don't have libxslt.
+PG_CPPFLAGS := $(shell xml2-config --cflags)
+
+ifeq ($(USE_LIBXSLT),1)
+PG_CPPFLAGS += -DUSE_LIBXSLT
 SHLIB_LINK = -lxslt -lxml2
+else
+SHLIB_LINK = -lxml2
+endif
 
 DATA_built = pgxml.sql
 DATA = uninstall_pgxml.sql
 REGRESS = xml2
 DOCS = README.xml2
 
-PG_CPPFLAGS := $(shell xml2-config --cflags)
-
 ifdef USE_PGXS
 PGXS := $(shell pg_config --pgxs)
 include $(PGXS)
@@ -24,4 +32,3 @@ top_builddir = ../..
 include $(top_builddir)/src/Makefile.global
 include $(top_srcdir)/contrib/contrib-global.mk
 endif
-

contrib/xml2/expected/xml2_1.out

@@ -0,0 +1,102 @@
+--
+-- first, define the functions.  Turn off echoing so that expected file
+-- does not depend on contents of pgxml.sql.
+--
+SET client_min_messages = warning;
+\set ECHO none
+RESET client_min_messages;
+select xslt_process( 
+'<table xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
+
+<row>
+  <x>1</x>
+</row>
+
+<row>
+  <x>2</x>
+</row>
+
+<row>
+  <x>3</x>
+</row>
+
+<row>
+  <x>4</x>
+</row>
+
+<row>
+  <x>5</x>
+</row>
+
+</table>'::text,
+$$<xsl:stylesheet version="1.0"
+               xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
+<xsl:output method="xml" indent="yes" />
+<xsl:template match="*">
+  <xsl:copy>
+     <xsl:copy-of select="@*" />
+     <xsl:apply-templates />
+  </xsl:copy>
+</xsl:template>
+<xsl:template match="comment()|processing-instruction()">
+  <xsl:copy />
+</xsl:template>
+</xsl:stylesheet>
+$$::text);
+ERROR:  xslt_process() is not available without libxslt
+CREATE TABLE xpath_test (id integer NOT NULL, t text);
+INSERT INTO xpath_test VALUES (1, '<doc><int>1</int></doc>');
+SELECT * FROM xpath_table('id', 't', 'xpath_test', '/doc/int', 'true')
+as t(id int4);
+ id 
+----
+(0 rows)
+
+SELECT * FROM xpath_table('id', 't', 'xpath_test', '/doc/int', 'true')
+as t(id int4, doc int4);
+ id | doc 
+----+-----
+  1 |   1
+(1 row)
+
+create table articles (article_id integer, article_xml text, date_entered date);
+insert into articles (article_id, article_xml, date_entered)
+values (2, '<article><author>test</author><pages>37</pages></article>', now());
+SELECT * FROM
+xpath_table('article_id',
+            'article_xml',
+            'articles',
+            '/article/author|/article/pages|/article/title',
+            'date_entered > ''2003-01-01'' ')
+AS t(article_id integer, author text, page_count integer, title text);
+ article_id | author | page_count | title 
+------------+--------+------------+-------
+          2 | test   |         37 | 
+(1 row)
+
+-- this used to fail when invoked a second time
+select xslt_process('<aaa/>',$$<xsl:stylesheet version="1.0"
+xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
+<xsl:template match="@*|node()">
+      <xsl:copy>
+         <xsl:apply-templates select="@*|node()"/>
+      </xsl:copy>
+   </xsl:template>
+</xsl:stylesheet>$$);
+ERROR:  xslt_process() is not available without libxslt
+select xslt_process('<aaa/>',$$<xsl:stylesheet version="1.0"
+xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
+<xsl:template match="@*|node()">
+      <xsl:copy>
+         <xsl:apply-templates select="@*|node()"/>
+      </xsl:copy>
+   </xsl:template>
+</xsl:stylesheet>$$);
+ERROR:  xslt_process() is not available without libxslt
+create table t1 (id integer, xml_data text);
+insert into t1 (id, xml_data)
+values
+(1, '<attributes><attribute name="attr_1">Some
+Value</attribute></attributes>');
+create index idx_xpath on t1 ( xpath_string
+('/attributes/attribute[@name="attr_1"]/text()', xml_data));

contrib/xml2/pgxml.sql.in

@@ -28,19 +28,14 @@ CREATE OR REPLACE FUNCTION xpath_list(text,text,text) RETURNS text
 	AS 'MODULE_PATHNAME'
 	LANGUAGE C STRICT IMMUTABLE;
 
-
 CREATE OR REPLACE FUNCTION xpath_list(text,text) RETURNS text 
 AS 'SELECT xpath_list($1,$2,'','')' LANGUAGE SQL STRICT IMMUTABLE;
 
-
-
 -- Wrapper functions for nodeset where no tags needed
 
-
 CREATE OR REPLACE FUNCTION xpath_nodeset(text,text) RETURNS text AS
 'SELECT xpath_nodeset($1,$2,'''','''')' LANGUAGE SQL STRICT IMMUTABLE;
 
-
 CREATE OR REPLACE FUNCTION xpath_nodeset(text,text,text) RETURNS text AS
 'SELECT xpath_nodeset($1,$2,'''',$3)' LANGUAGE SQL STRICT IMMUTABLE;
 
@@ -51,14 +46,10 @@ CREATE OR REPLACE FUNCTION xpath_table(text,text,text,text,text) RETURNS setof r
 	LANGUAGE C STRICT STABLE;
 
 -- XSLT functions
--- Delete from here to the end of the file if you are not compiling with
--- XSLT support.
-
 
 CREATE OR REPLACE FUNCTION xslt_process(text,text,text) RETURNS text 
 	AS 'MODULE_PATHNAME' LANGUAGE C STRICT VOLATILE;
 
 -- the function checks for the correct argument count
-
 CREATE OR REPLACE FUNCTION xslt_process(text,text) RETURNS text 
 	AS 'MODULE_PATHNAME' LANGUAGE C STRICT IMMUTABLE;

contrib/xml2/xslt_proc.c

@@ -7,6 +7,8 @@
 #include "funcapi.h"
 #include "miscadmin.h"
 
+#ifdef USE_LIBXSLT
+
 /* libxml includes */
 
 #include <libxml/xpath.h>
@@ -20,11 +22,15 @@
 #include <libxslt/transform.h>
 #include <libxslt/xsltutils.h>
 
+#endif /* USE_LIBXSLT */
+
 
 /* externally accessible functions */
 
 Datum		xslt_process(PG_FUNCTION_ARGS);
 
+#ifdef USE_LIBXSLT
+
 /* declarations to come from xpath.c */
 extern void elog_error(const char *explain, bool force);
 extern void pgxml_parser_init(void);
@@ -36,13 +42,15 @@ static void parse_params(const char **params, text *paramstr);
 
 #define GET_STR(textp) DatumGetCString(DirectFunctionCall1(textout, PointerGetDatum(textp)))
 
+#endif /* USE_LIBXSLT */
+
 
 PG_FUNCTION_INFO_V1(xslt_process);
 
 Datum
 xslt_process(PG_FUNCTION_ARGS)
 {
-
+#ifdef USE_LIBXSLT
 
 	const char *params[MAXPARAMS + 1];	/* +1 for the terminator */
 	xsltStylesheetPtr stylesheet = NULL;
@@ -58,7 +66,6 @@ xslt_process(PG_FUNCTION_ARGS)
 	text	   *paramstr;
 	text	   *tres;
 
-
 	if (fcinfo->nargs == 3)
 	{
 		paramstr = PG_GETARG_TEXT_P(2);
@@ -128,8 +135,18 @@ xslt_process(PG_FUNCTION_ARGS)
 	VARATT_SIZEP(tres) = reslen + VARHDRSZ;
 
 	PG_RETURN_TEXT_P(tres);
+
+#else /* !USE_LIBXSLT */
+
+	ereport(ERROR,
+			(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+			 errmsg("xslt_process() is not available without libxslt")));
+	PG_RETURN_NULL();
+
+#endif /* USE_LIBXSLT */
 }
 
+#ifdef USE_LIBXSLT
 
 static void
 parse_params(const char **params, text *paramstr)
@@ -178,3 +195,5 @@ parse_params(const char **params, text *paramstr)
 
 	params[i] = NULL;
 }
+
+#endif /* USE_LIBXSLT */