Fix trix parser to allow lowercase trix, add tests (#1966)

Changed TriX parser to allow `trix` and `TriX`

The RDFLib TriX parser currently only accepts TriX documents conforming to the the [Nokia-published XSD](https://web.archive.org/web/20040821093939/http://swdev.nokia.com/trix/trix-1.0.xsd) which specifies (the mixed-case) `TriX`, contradicting the [W3C-published XSD spec for TriX](https://www.w3.org/2004/03/trix/trix-1/trix-1.0.xsd) which specifies (the lower-case) `trix`. We should accept both.

We were also a bit light on a TriX test suite for exercising the parser, so I recruited some TriX test fixtures from NG4J and Jena and fleshed out the TriX test suite, using the W3C "Manifest"-style approach.

rdflib/plugins/parsers/trix.py

@@ -56,7 +56,7 @@ def startElementNS(self, name, qname, attrs):
                 % (name[0], TRIXNS)
             )
 
-        if name[1] == "TriX":
+        if name[1].lower() == "trix":
             if self.state == 0:
                 self.state = 1
             else:
@@ -205,7 +205,7 @@ def endElementNS(self, name, qname):
             self.graph = None
             self.state = 1
 
-        elif name[1] == "TriX":
+        elif name[1].lower() == "trix":
             self.state = 0
 
         else:

test/data/suites/trix/README

@@ -0,0 +1,42 @@
+This README is adapted from the README of the W3C RDF Working Group's
+TriG test suite and modified for use with RDFLib's informally-assembled
+TrIX test suite. This test suite contains three kinds of tests:
+
+  Evaluation (rdft:TestTrixEval) - a pair of an input trig file
+  and reference ntriples file.
+
+  Positive syntax (rdft:TestTrixPositiveSyntax) - an input trig
+  file with no syntax errors.
+
+  Negative syntax (rdft:TestTrixNegativeSyntax) - an input trig
+  file with at least one syntax error.
+
+The manifest.ttl file in this directory lists all of the tests in the
+RDFLib TriX test suite. Each test is one of the above tests. All
+tests have a name (mf:name) and an input (mf:action). The Evaluation
+tests have an expected result (mf:result).
+
+• An implementation passes an Evaluation test if it parses the input
+  into a graph, parses the expecte result into another graph, and
+  those two graphs are isomorphic (see
+  <http://www.w3.org/TR/rdf11-concepts/#graph-isomorphism>).
+
+• An implementation passes a positive syntax test if it parses the
+  input.
+
+• An implementation passes a negative syntax test if it fails to parse
+  the input.
+
+The IRI for the test suite is <https://rdflib.github.io/tests/trix/>.
+Per RFC 3986 section 5.1.3, the base IRI for parsing each file is the
+retrieval IRI for that file. For example, the tests trig-subm-01 and
+trig-subm-27 require relative IRI resolution against a base of
+<https://rdflib.github.io/tests/trix/trig-subm-01.trix> and
+<https://rdflib.github.io/tests/trix/strig-subm-27.trix> respectively.
+
+
+Adapted from https://github.com/w3c/rdf-tests/blob/main/trig/README,
+authors:
+
+Eric Prud'hommeaux <eric+turtle@w3.org> - 11 June 2013.
+Gregg Kellogg <gregg@greggkellogg.net> - 12 June 2013.

test/data/suites/trix/extension1.xsl

@@ -0,0 +1,20 @@
+<?xml version="1.0"?>
+<!-- Replaces any XML document by a hard-coded TriX document containing
+	one graph with one triple -->
+<xsl:stylesheet 
+		xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
+		xmlns="http://www.w3.org/2004/03/trix/trix-1/"
+		xmlns:ex="http://example.com/#"
+		version="2.0">
+	<xsl:template match="/">
+		<TriX>
+			<graph>
+				<triple>
+					<qname>ex:a</qname>
+					<qname>ex:b</qname>
+					<qname>ex:c</qname>
+				</triple>
+			</graph>
+		</TriX>
+	</xsl:template>
+</xsl:stylesheet>

test/data/suites/trix/extension2.xsl

@@ -0,0 +1,33 @@
+<?xml version="1.0"?>
+<!-- Expands <qname>ns:foo</qname> to <uri>.....foo</uri> using xmlns:ns -->
+<xsl:stylesheet 
+		xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
+		xmlns="http://www.w3.org/2004/03/trix/trix-1/"
+		xmlns:trix="http://www.w3.org/2004/03/trix/trix-1/"
+		xmlns:ex="http://example.com/#"
+		version="2.0">
+
+	<!-- Expand qnames -->
+	<xsl:template match="trix:qname">
+		<uri>
+			<xsl:variable name="ns">
+				<xsl:value-of select="substring-before(text(),':')"/>
+			</xsl:variable>
+			<xsl:value-of select="namespace::*[local-name()=$ns]"/>
+			<xsl:value-of select="substring-after(text(),':')"/>
+		</uri>
+	</xsl:template>
+
+	<!-- Not necessary, but avoids namespace declarations scattered through
+		the result document -->
+	<xsl:template match="trix:TriX">
+		<TriX><xsl:apply-templates/></TriX>
+	</xsl:template>
+
+	<!-- This is a simple identity function -->
+	<xsl:template match="@*|*|processing-instruction()|comment()" priority="-2">
+		<xsl:copy>
+			<xsl:apply-templates select="*|@*|text()|processing-instruction()|comment()"/>
+		</xsl:copy>
+	</xsl:template>
+</xsl:stylesheet>