Subject: [PATCH] [core-updates] Add option --xpath0 to xmllint from libxml2
From: david larsson <[email-masked]>
To: [email-masked]
Date: Mon, 19 Apr 2021 20:48:47 +0200
List-Id: <debbugs-submit.debbugs.gnu.org>

Hi!
This patch adds the option to separate xpath results from xmllint by a 
null delimiter when using the --xpath0 option-flag. It is something 
that's been asked for for a long time by users on stackoverflow and 
merge-attempts have been made to upstream without success.

Examples:
   - https://gitlab.gnome.org/GNOME/libxml2/-/issues/227
   - https://gitlab.gnome.org/GNOME/libxml2/-/merge_requests/8

Best regards,
David

From 714a6a26da55f7e06c94d3d2bb2965b9d2f832da Mon Sep 17 00:00:00 2001
From: David Larsson <[email-masked]>
Date: Mon, 19 Apr 2021 20:39:23 +0200
Subject: [PATCH] gnu: libxml2: Add patch for xpath0 option to xmllint.

* gnu/packages/patches/libxml2-Add-option-xpath0.patch: New file...
* gnu/packages/xml.scm (libxml2) [source]: ...add it.
---
 .../patches/libxml2-Add-option-xpath0.patch   | 139 ++++++++++++++++++
 gnu/packages/xml.scm                          |   3 +-
 2 files changed, 141 insertions(+), 1 deletion(-)
 create mode 100644 gnu/packages/patches/libxml2-Add-option-xpath0.patch

diff --git a/gnu/packages/patches/libxml2-Add-option-xpath0.patch b/gnu/packages/patches/libxml2-Add-option-xpath0.patch
new file mode 100644
index 0000000000..3337374a8c
--- /dev/null
+++ b/gnu/packages/patches/libxml2-Add-option-xpath0.patch
@@ -0,0 +1,139 @@
+From e1df743329bdfd94fbfdea18303c5c6c6fe13403 Mon Sep 17 00:00:00 2001
+From: methuselah-0 <[email-masked]>
+Date: Thu, 1 Apr 2021 08:33:56 +0200
+Subject: [PATCH] Add option --xpath0
+
+---
+ doc/xmllint.xml | 16 ++++++++++++++++
+ xmllint.c       | 32 +++++++++++++++++++++++---------
+ 2 files changed, 39 insertions(+), 9 deletions(-)
+
+diff --git a/doc/xmllint.xml b/doc/xmllint.xml
+index 1008179b..fcdc237e 100644
+--- a/doc/xmllint.xml
++++ b/doc/xmllint.xml
+@@ -70,6 +70,7 @@
+ 			<arg choice="plain"><option>--debug</option></arg>
+ 			<arg choice="plain"><option>--shell</option></arg>
+ 			<arg choice="plain"><option>--xpath "<replaceable class="option">XPath_expression</replaceable>"</option></arg>
++			<arg choice="plain"><option>--xpath0 "<replaceable class="option">XPath_expression</replaceable>"</option></arg>
+ 			<arg choice="plain"><option>--debugent</option></arg>
+ 			<arg choice="plain"><option>--copy</option></arg>
+ 			<arg choice="plain"><option>--recover</option></arg>
+@@ -537,6 +538,21 @@
+ 			node set is serialized in full in the output. In case
+ 			of an empty node set the "XPath set is empty" result
+ 			will be shown and an error exit code will be returned.
++			Results are separated by the newline character.
++		</para>
++	</listitem>
++		</varlistentry>
++
++		<varlistentry>
++	<term><option>--xpath0 "<replaceable class="option">XPath_expression</replaceable>"</option></term>
++	<listitem>
++		<para>
++			Run an XPath expression given as argument and print the
++			result. In case of a nodeset result, each node in the
++			node set is serialized in full in the output. In case
++			of an empty node set the "XPath set is empty" result
++			will be shown and an error exit code will be returned.
++			Results are separated by the null character.
+ 		</para>
+ 	</listitem>
+ 		</varlistentry>
+diff --git a/xmllint.c b/xmllint.c
+index 6ca1bf54..a60e1f4f 100644
+--- a/xmllint.c
++++ b/xmllint.c
+@@ -194,6 +194,7 @@ static int sax1 = 0;
+ #endif /* LIBXML_SAX1_ENABLED */
+ #ifdef LIBXML_XPATH_ENABLED
+ static const char *xpathquery = NULL;
++static const char *xpathsep = "\n";
+ #endif
+ static int options = XML_PARSE_COMPACT | XML_PARSE_BIG_LINES;
+ static int sax = 0;
+@@ -2095,7 +2096,7 @@ static void doXPathDump(xmlXPathObjectPtr cur) {
+             for (i = 0;i < cur->nodesetval->nodeNr;i++) {
+                 node = cur->nodesetval->nodeTab[i];
+                 xmlNodeDumpOutput(buf, NULL, node, 0, 0, NULL);
+-                xmlOutputBufferWrite(buf, 1, "\n");
++		xmlOutputBufferWrite(buf, 1, xpathsep);
+             }
+             xmlOutputBufferClose(buf);
+ #else
+@@ -2104,27 +2105,27 @@ static void doXPathDump(xmlXPathObjectPtr cur) {
+ 	    break;
+         }
+         case XPATH_BOOLEAN:
+-	    if (cur->boolval) printf("true\n");
+-	    else printf("false\n");
++	    if (cur->boolval) printf("true%s", xpathsep);
++	    else printf("false%s", xpathsep);
+ 	    break;
+         case XPATH_NUMBER:
+ 	    switch (xmlXPathIsInf(cur->floatval)) {
+ 	    case 1:
+-		printf("Infinity\n");
++	        printf("Infinity%s", xpathsep);
+ 		break;
+ 	    case -1:
+-		printf("-Infinity\n");
++	        printf("-Infinity%s", xpathsep);
+ 		break;
+ 	    default:
+ 		if (xmlXPathIsNaN(cur->floatval)) {
+-		    printf("NaN\n");
++		    printf("NaN%s", xpathsep);
+ 		} else {
+-		    printf("%0g\n", cur->floatval);
++		    printf("%0g%s", cur->floatval, xpathsep);
+ 		}
+ 	    }
+ 	    break;
+         case XPATH_STRING:
+-	    printf("%s\n", (const char *) cur->stringval);
++	    printf("%s%s", (const char *) cur->stringval, xpathsep);
+ 	    break;
+         case XPATH_UNDEFINED:
+ 	    fprintf(stderr, "XPath Object is uninitialized\n");
+@@ -3098,7 +3099,8 @@ static void usage(FILE *f, const char *name) {
+     fprintf(f, "\t--sax: do not build a tree but work just at the SAX level\n");
+     fprintf(f, "\t--oldxml10: use XML-1.0 parsing rules before the 5th edition\n");
+ #ifdef LIBXML_XPATH_ENABLED
+-    fprintf(f, "\t--xpath expr: evaluate the XPath expression, imply --noout\n");
++    fprintf(f, "\t--xpath expr: evaluate the XPath expression, results are separated by \\n, imply --noout\n");
++    fprintf(f, "\t--xpath0 expr: evaluate the XPath expression, results are separated by \\0, imply --noout\n");
+ #endif
+ 
+     fprintf(f, "\nLibxml project home page: http://xmlsoft.org/\n");
+@@ -3480,6 +3482,13 @@ main(int argc, char **argv) {
+ 	    i++;
+ 	    noout++;
+ 	    xpathquery = argv[i];
++	    xpathsep = "\n";
++        } else if ((!strcmp(argv[i], "-xpath0")) ||
++                   (!strcmp(argv[i], "--xpath0"))) {
++	    i++;
++	    noout++;
++	    xpathquery = argv[i];
++	    xpathsep = "\0";
+ #endif
+ 	} else if ((!strcmp(argv[i], "-oldxml10")) ||
+ 	           (!strcmp(argv[i], "--oldxml10"))) {
+@@ -3712,6 +3721,11 @@ main(int argc, char **argv) {
+ 	    i++;
+ 	    continue;
+ 	}
++        if ((!strcmp(argv[i], "-xpath0")) ||
++	    (!strcmp(argv[i], "--xpath0"))) {
++	    i++;
++	    continue;
++	}
+ #endif
+ 	if ((timing) && (repeat))
+ 	    startTimer();
+-- 
+2.30.2
+
diff --git a/gnu/packages/xml.scm b/gnu/packages/xml.scm
index ad5f35ef1e..d6a9b46e1d 100644
--- a/gnu/packages/xml.scm
+++ b/gnu/packages/xml.scm
@@ -177,7 +177,8 @@ hierarchical form with variable field lengths.")
                                  version ".tar.gz"))
              (sha256
               (base32
-               "07xynh8hcxb2yb1fs051xrgszjvj37wnxvxgsj10rzmqzy9y3zma"))))
+               "07xynh8hcxb2yb1fs051xrgszjvj37wnxvxgsj10rzmqzy9y3zma"))
+             (patches (list (search-patch "libxml2-Add-option-xpath0.patch")))))
     (build-system gnu-build-system)
     (outputs '("out" "static" "doc"))
     (arguments
-- 
2.30.2