[libxml2] Fix unability to validate ambiguously constructed interleave for RelaxNG

[Nick Wellnhofer <nwellnhof src gnome org>]

commit 8074b881792b354b0e8c1b4076c5f41efd951a52
Author: Jan Pokorný <jpokorny redhat com>
Date:   Thu Aug 8 23:33:48 2019 +0200

    Fix unability to validate ambiguously constructed interleave for RelaxNG
    
    Previously, test/relaxng/ambig_name-class.xml would fail to validate
    for a simple reason -- interleave within "open-name-class" context
    is supposed to be fine with whatever else is pending the consumption,
    since effectively, it's unrelated from a higher parsing perspective.
    
    Signed-off-by: Jan Pokorný <jpokorny redhat com>

 relaxng.c                             | 12 +++++++++++-
 result/relaxng/ambig_name-class_err   |  1 +
 result/relaxng/ambig_name-class_valid |  0
 test/relaxng/ambig_name-class.rng     |  1 +
 test/relaxng/ambig_name-class.xml     | 16 ++++++++++++++++
 5 files changed, 29 insertions(+), 1 deletion(-)
---
diff --git a/relaxng.c b/relaxng.c
index 2f13cbdd..1c337e3d 100644
--- a/relaxng.c
+++ b/relaxng.c
@@ -9476,7 +9476,17 @@ xmlRelaxNGValidateInterleave(xmlRelaxNGValidCtxtPtr ctxt,
             xmlRelaxNGFreeValidState(ctxt, oldstate);
             oldstate = ctxt->state;
             ctxt->state = NULL;
-            if (cur != NULL) {
+            if (cur != NULL
+                    /* there's a nasty violation of context-free unambiguities,
+                       since in open-name-class context, interleave in the
+                       production shall finish without caring about anything
+                       else that is OK to follow in that case -- it would
+                       otherwise get marked as "extra content" and would
+                       hence fail the validation, hence this perhaps
+                       dirty attempt to rectify such a situation */
+                    && (define->parent->type != XML_RELAXNG_DEF
+                        || !xmlStrEqual(define->parent->name,
+                                        (const xmlChar *) "open-name-class"))) {
                 VALID_ERR2(XML_RELAXNG_ERR_INTEREXTRA, cur->name);
                 ret = -1;
                 ctxt->state = oldstate;
diff --git a/result/relaxng/ambig_name-class_err b/result/relaxng/ambig_name-class_err
new file mode 100644
index 00000000..0afe5cd6
--- /dev/null
+++ b/result/relaxng/ambig_name-class_err
@@ -0,0 +1 @@
+./test/relaxng/ambig_name-class.rng validates
diff --git a/result/relaxng/ambig_name-class_valid b/result/relaxng/ambig_name-class_valid
new file mode 100644
index 00000000..e69de29b
diff --git a/test/relaxng/ambig_name-class.rng b/test/relaxng/ambig_name-class.rng
new file mode 120000
index 00000000..08533d39
--- /dev/null
+++ b/test/relaxng/ambig_name-class.rng
@@ -0,0 +1 @@
+tutorA.rng
\ No newline at end of file
diff --git a/test/relaxng/ambig_name-class.xml b/test/relaxng/ambig_name-class.xml
new file mode 100644
index 00000000..de673f2e
--- /dev/null
+++ b/test/relaxng/ambig_name-class.xml
@@ -0,0 +1,16 @@
+<grammar xmlns="http://relaxng.org/ns/structure/1.0"; >
+  <start>
+    <element name="foo">
+      <attribute>
+        <choice>
+          <name>alpha</name>
+          <name>bravo</name>
+        </choice>
+        <choice>
+          <value>none</value>
+          <value>all</value>
+        </choice>
+      </attribute>
+    </element>
+  </start>
+</grammar>