fix(cruby): SAX and Push parser error handling in the presence of foreign handlers

CHANGELOG.md

@@ -4,6 +4,13 @@ Nokogiri follows [Semantic Versioning](https://semver.org/), please see the [REA
 
 ---
 
+## v1.11.1 / unreleased
+
+### Fixed
+
+* [CRuby] If `libxml-ruby` is loaded before `nokogiri`, the SAX and Push parsers no longer call `libxml-ruby`'s handlers. Instead, they defensively override the libxml2 global handler before parsing. [[#2168](https://github.com/sparklemotion/nokogiri/issues/2168)]
+
+
 ## v1.11.0 / 2021-01-03
 
 ### Notes

ext/nokogiri/html_sax_parser_context.c

@@ -92,6 +92,8 @@ parse_with(VALUE self, VALUE sax_handler)
     ctxt->sax = sax;
     ctxt->userData = (void *)NOKOGIRI_SAX_TUPLE_NEW(ctxt, sax_handler);
 
+    xmlSetStructuredErrorFunc(NULL, NULL);
+
     rb_ensure(parse_doc, (VALUE)ctxt, parse_doc_finalize, (VALUE)ctxt);
 
     return self;

ext/nokogiri/html_sax_push_parser.c

@@ -9,9 +9,10 @@
 static VALUE native_write(VALUE self, VALUE _chunk, VALUE _last_chunk)
 {
   xmlParserCtxtPtr ctx;
-  const char * chunk  = NULL;
-  int size            = 0;
-
+  const char * chunk = NULL;
+  int size = 0;
+  int status = 0;
+  libxmlStructuredErrorHandlerState handler_state;
 
   Data_Get_Struct(self, xmlParserCtxt, ctx);
 
@@ -20,11 +21,16 @@ static VALUE native_write(VALUE self, VALUE _chunk, VALUE _last_chunk)
     size = (int)RSTRING_LEN(_chunk);
   }
 
-  if(htmlParseChunk(ctx, chunk, size, Qtrue == _last_chunk ? 1 : 0)) {
-    if (!(ctx->options & XML_PARSE_RECOVER)) {
-      xmlErrorPtr e = xmlCtxtGetLastError(ctx);
-      Nokogiri_error_raise(NULL, e);
-    }
+  Nokogiri_structured_error_func_save_and_set(&handler_state, NULL, NULL);
+
+  status = htmlParseChunk(ctx, chunk, size, Qtrue == _last_chunk ? 1 : 0);
+
+  Nokogiri_structured_error_func_restore(&handler_state);
+
+  if ((status != 0) && !(ctx->options & XML_PARSE_RECOVER)) {
+    // TODO: there appear to be no tests for this block
+    xmlErrorPtr e = xmlCtxtGetLastError(ctx);
+    Nokogiri_error_raise(NULL, e);
   }
 
   return self;

ext/nokogiri/nokogiri.c

@@ -1,5 +1,7 @@
 #include <nokogiri.h>
 
+void init_test_global_handlers(); /* in lieu of test_global_handlers.h */
+
 VALUE mNokogiri ;
 VALUE mNokogiriXml ;
 VALUE mNokogiriHtml ;
@@ -132,4 +134,5 @@ void Init_nokogiri()
   init_xml_relax_ng();
   init_nokogiri_io();
   init_xml_encoding_handler();
+  init_test_global_handlers();
 }

ext/nokogiri/test_global_handlers.c

@@ -0,0 +1,41 @@
+#include <nokogiri.h>
+#include "libxml/xmlerror.h"
+
+static VALUE foreign_error_handler_block = Qnil;
+
+static void foreign_error_handler(void* user_data, xmlErrorPtr c_error)
+{
+  rb_funcall(foreign_error_handler_block, rb_intern("call"), 0);
+}
+
+/*
+ * call-seq:
+ *   __foreign_error_handler { ... } -> nil
+ *
+ * Override libxml2's global error handlers to call the block. This method thus has very little
+ * value except to test that Nokogiri is properly setting error handlers elsewhere in the code. See
+ * test/helper.rb for how this is being used.
+ */
+static VALUE
+rb_foreign_error_handler(VALUE klass)
+{
+  rb_need_block();
+  foreign_error_handler_block = rb_block_proc();
+  xmlSetStructuredErrorFunc(NULL, foreign_error_handler);
+  return Qnil;
+}
+
+/*
+ *  Document-module: Nokogiri::Test
+ *
+ *  The Nokogiri::Test module should only be used for testing Nokogiri.
+ *  Do NOT use this outside of the Nokogiri test suite.
+ */
+void
+init_test_global_handlers()
+{
+  VALUE mNokogiri = rb_define_module("Nokogiri");
+  VALUE mNokogiriTest = rb_define_module_under(mNokogiri, "Test");
+
+  rb_define_singleton_method(mNokogiriTest, "__foreign_error_handler", rb_foreign_error_handler, 0);
+}

ext/nokogiri/xml_sax_parser_context.c

@@ -120,6 +120,8 @@ parse_with(VALUE self, VALUE sax_handler)
     ctxt->sax = sax;
     ctxt->userData = (void *)NOKOGIRI_SAX_TUPLE_NEW(ctxt, sax_handler);
 
+    xmlSetStructuredErrorFunc(NULL, NULL);
+
     rb_ensure(parse_doc, (VALUE)ctxt, parse_doc_finalize, (VALUE)ctxt);
 
     return Qnil;

ext/nokogiri/xml_sax_push_parser.c

@@ -35,6 +35,8 @@ static VALUE native_write(VALUE self, VALUE _chunk, VALUE _last_chunk)
     size = (int)RSTRING_LEN(_chunk);
   }
 
+  xmlSetStructuredErrorFunc(NULL, NULL);
+
   if (xmlParseChunk(ctx, chunk, size, Qtrue == _last_chunk ? 1 : 0)) {
     if (!(ctx->options & XML_PARSE_RECOVER)) {
       xmlErrorPtr e = xmlCtxtGetLastError(ctx);

ext/nokogiri/xml_syntax_error.c

@@ -1,5 +1,28 @@
 #include <xml_syntax_error.h>
 
+void
+Nokogiri_structured_error_func_save(libxmlStructuredErrorHandlerState *handler_state)
+{
+  /* this method is tightly coupled to the implementation of xmlSetStructuredErrorFunc */
+  handler_state->user_data = xmlStructuredErrorContext;
+  handler_state->handler = xmlStructuredError;
+}
+
+void
+Nokogiri_structured_error_func_save_and_set(libxmlStructuredErrorHandlerState *handler_state,
+                                            void *user_data,
+                                            xmlStructuredErrorFunc handler)
+{
+  Nokogiri_structured_error_func_save(handler_state);
+  xmlSetStructuredErrorFunc(user_data, handler);
+}
+
+void
+Nokogiri_structured_error_func_restore(libxmlStructuredErrorHandlerState *handler_state)
+{
+  xmlSetStructuredErrorFunc(handler_state->user_data, handler_state->handler);
+}
+
 void Nokogiri_error_array_pusher(void * ctx, xmlErrorPtr error)
 {
   VALUE list = (VALUE)ctx;

ext/nokogiri/xml_syntax_error.h

@@ -3,11 +3,23 @@
 
 #include <nokogiri.h>
 
+typedef struct _libxmlStructuredErrorHandlerState {
+  void *user_data;
+  xmlStructuredErrorFunc handler;
+} libxmlStructuredErrorHandlerState ;
+
 void init_xml_syntax_error();
+
+void Nokogiri_structured_error_func_save(libxmlStructuredErrorHandlerState *handler_state);
+void Nokogiri_structured_error_func_save_and_set(libxmlStructuredErrorHandlerState *handler_state,
+                                                 void *user_data,
+                                                 xmlStructuredErrorFunc handler);
+void Nokogiri_structured_error_func_restore(libxmlStructuredErrorHandlerState *handler_state);
+
 VALUE Nokogiri_wrap_xml_syntax_error(xmlErrorPtr error);
-void Nokogiri_error_array_pusher(void * ctx, xmlErrorPtr error);
-NORETURN(void Nokogiri_error_raise(void * ctx, xmlErrorPtr error));
+void Nokogiri_error_array_pusher(void *ctx, xmlErrorPtr error);
+NORETURN(void Nokogiri_error_raise(void *ctx, xmlErrorPtr error));
 
 extern VALUE cNokogiriXmlSyntaxError;
-#endif
 
+#endif /* NOKOGIRI_XML_SYNTAX_ERROR */

test/helper.rb

@@ -58,7 +58,16 @@ class TestCase < MiniTest::Spec
     XSLT_FILE           = File.join(ASSETS_DIR, 'staff.xslt')
     XPATH_FILE          = File.join(ASSETS_DIR, 'slow-xpath.xml')
 
+    def setup
+      @fake_error_handler_called = false
+      Nokogiri::Test.__foreign_error_handler do
+        @fake_error_handler_called = true
+      end if Nokogiri.uses_libxml?
+    end
+
     def teardown
+      refute(@fake_error_handler_called, "the fake error handler should never get called") if Nokogiri.uses_libxml?
+
       if ENV['NOKOGIRI_GC']
         STDOUT.putc '!'
         if RUBY_PLATFORM =~ /java/
@@ -135,6 +144,11 @@ class Doc < XML::SAX::Document
         attr_reader :xmldecls
         attr_reader :processing_instructions
 
+        def initialize
+          @errors = []
+          super
+        end
+
         def xmldecl version, encoding, standalone
           @xmldecls = [version, encoding, standalone].compact
           super

test/namespaces/test_namespaces_preservation.rb

@@ -5,6 +5,7 @@ module XML
     class TestNamespacePreservation < Nokogiri::TestCase
 
       def setup
+        super
         @xml = Nokogiri.XML <<-eoxml
               <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">
                 <xs:element xmlns:quer="http://api.geotrust.com/webtrust/query"/>

test/test_xslt_transforms.rb

@@ -2,6 +2,7 @@
 
 class TestXsltTransforms < Nokogiri::TestCase
   def setup
+    super
     @doc = Nokogiri::XML(File.open(XML_FILE))
   end
 

test/xml/sax/test_parser_context.rb

@@ -7,6 +7,7 @@ module XML
     module SAX
       class TestParserContext < Nokogiri::SAX::TestCase
         def setup
+          super
           @xml = '<hello>
 
 world

test/xml/test_relax_ng.rb

@@ -4,6 +4,7 @@ module Nokogiri
   module XML
     class TestRelaxNG < Nokogiri::TestCase
       def setup
+        super
         assert @schema = Nokogiri::XML::RelaxNG(File.read(ADDRESS_SCHEMA_FILE))
       end
 

test/xml/test_schema.rb

@@ -4,6 +4,7 @@ module Nokogiri
   module XML
     class TestSchema < Nokogiri::TestCase
       def setup
+        super
         assert @xsd = Nokogiri::XML::Schema(File.read(PO_SCHEMA_FILE))
       end
 

test/xml/test_unparented_node.rb

@@ -6,6 +6,7 @@ module Nokogiri
   module XML
     class TestUnparentedNode < Nokogiri::TestCase
       def setup
+        super
         begin
           xml = Nokogiri::XML.parse(File.read(XML_FILE), XML_FILE)
           @node = xml.at('staff')