bpo-35018: Sax parser should provide user access to lexical handlers (GH-20958)
Co-Authored-By: Jonathan Gossage <jgossage@gmail.com>
This commit is contained in:
Zackery Spytz
GitHub
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@ -11,12 +11,12 @@
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--------------
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The SAX API defines four kinds of handlers: content handlers, DTD handlers,
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error handlers, and entity resolvers. Applications normally only need to
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implement those interfaces whose events they are interested in; they can
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implement the interfaces in a single object or in multiple objects. Handler
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implementations should inherit from the base classes provided in the module
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:mod:`xml.sax.handler`, so that all methods get default implementations.
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The SAX API defines five kinds of handlers: content handlers, DTD handlers,
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error handlers, entity resolvers and lexical handlers. Applications normally
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only need to implement those interfaces whose events they are interested in;
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they can implement the interfaces in a single object or in multiple objects.
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Handler implementations should inherit from the base classes provided in the
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module :mod:`xml.sax.handler`, so that all methods get default implementations.
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.. class:: ContentHandler
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@ -47,6 +47,12 @@ implementations should inherit from the base classes provided in the module
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application. The methods of this object control whether errors are immediately
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converted to exceptions or are handled in some other way.
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.. class:: LexicalHandler
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Interface used by the parser to represent low freqency events which may not
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be of interest to many applications.
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In addition to these classes, :mod:`xml.sax.handler` provides symbolic constants
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for the feature and property names.
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@ -114,7 +120,7 @@ for the feature and property names.
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.. data:: property_lexical_handler
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| value: ``"http://xml.org/sax/properties/lexical-handler"``
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| data type: xml.sax.sax2lib.LexicalHandler (not supported in Python 2)
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| data type: xml.sax.handler.LexicalHandler (not supported in Python 2)
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| description: An optional extension handler for lexical events like
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comments.
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| access: read/write
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@ -413,3 +419,45 @@ the passed-in exception object.
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information will continue to be passed to the application. Raising an exception
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in this method will cause parsing to end.
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.. _lexical-handler-objects:
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LexicalHandler Objects
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----------------------
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Optional SAX2 handler for lexical events.
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This handler is used to obtain lexical information about an XML
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document. Lexical information includes information describing the
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document encoding used and XML comments embedded in the document, as
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well as section boundaries for the DTD and for any CDATA sections.
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The lexical handlers are used in the same manner as content handlers.
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Set the LexicalHandler of an XMLReader by using the setProperty method
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with the property identifier
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``'http://xml.org/sax/properties/lexical-handler'``.
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.. method:: LexicalHandler.comment(content)
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Reports a comment anywhere in the document (including the DTD and
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outside the document element).
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.. method:: LexicalHandler.startDTD(name, public_id, system_id)
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Reports the start of the DTD declarations if the document has an
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associated DTD.
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.. method:: LexicalHandler.endDTD()
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Reports the end of DTD declaration.
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.. method:: LexicalHandler.startCDATA()
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Reports the start of a CDATA marked section.
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The contents of the CDATA marked section will be reported through
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the characters handler.
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.. method:: LexicalHandler.endCDATA()
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Reports the end of a CDATA marked section.
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@ -139,6 +139,13 @@ Add :data:`sys.orig_argv` attribute: the list of the original command line
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arguments passed to the Python executable.
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(Contributed by Victor Stinner in :issue:`23427`.)
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xml
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---
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Add a :class:`~xml.sax.handler.LexicalHandler` class to the
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:mod:`xml.sax.handler` module.
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(Contributed by Jonathan Gossage and Zackery Spytz in :issue:`35018`.)
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Optimizations
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=============
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@ -13,7 +13,8 @@ except SAXReaderNotAvailable:
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from xml.sax.saxutils import XMLGenerator, escape, unescape, quoteattr, \
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XMLFilterBase, prepare_input_source
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from xml.sax.expatreader import create_parser
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from xml.sax.handler import feature_namespaces, feature_external_ges
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from xml.sax.handler import (feature_namespaces, feature_external_ges,
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LexicalHandler)
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from xml.sax.xmlreader import InputSource, AttributesImpl, AttributesNSImpl
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from io import BytesIO, StringIO
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import codecs
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@ -1356,6 +1357,155 @@ class XmlReaderTest(XmlTestBase):
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self.assertEqual(attrs.getQNameByName((ns_uri, "attr")), "ns:attr")
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class LexicalHandlerTest(unittest.TestCase):
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def setUp(self):
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self.parser = None
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self.specified_version = '1.0'
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self.specified_encoding = 'UTF-8'
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self.specified_doctype = 'wish'
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self.specified_entity_names = ('nbsp', 'source', 'target')
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self.specified_comment = ('Comment in a DTD',
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'Really! You think so?')
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self.test_data = StringIO()
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self.test_data.write('<?xml version="{}" encoding="{}"?>\n'.
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format(self.specified_version,
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self.specified_encoding))
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self.test_data.write('<!DOCTYPE {} [\n'.
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format(self.specified_doctype))
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self.test_data.write('<!-- {} -->\n'.
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format(self.specified_comment[0]))
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self.test_data.write('<!ELEMENT {} (to,from,heading,body,footer)>\n'.
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format(self.specified_doctype))
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self.test_data.write('<!ELEMENT to (#PCDATA)>\n')
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self.test_data.write('<!ELEMENT from (#PCDATA)>\n')
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self.test_data.write('<!ELEMENT heading (#PCDATA)>\n')
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self.test_data.write('<!ELEMENT body (#PCDATA)>\n')
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self.test_data.write('<!ELEMENT footer (#PCDATA)>\n')
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self.test_data.write('<!ENTITY {} " ">\n'.
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format(self.specified_entity_names[0]))
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self.test_data.write('<!ENTITY {} "Written by: Alexander.">\n'.
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format(self.specified_entity_names[1]))
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self.test_data.write('<!ENTITY {} "Hope it gets to: Aristotle.">\n'.
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format(self.specified_entity_names[2]))
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self.test_data.write(']>\n')
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self.test_data.write('<{}>'.format(self.specified_doctype))
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self.test_data.write('<to>Aristotle</to>\n')
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self.test_data.write('<from>Alexander</from>\n')
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self.test_data.write('<heading>Supplication</heading>\n')
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self.test_data.write('<body>Teach me patience!</body>\n')
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self.test_data.write('<footer>&{};&{};&{};</footer>\n'.
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format(self.specified_entity_names[1],
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self.specified_entity_names[0],
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self.specified_entity_names[2]))
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self.test_data.write('<!-- {} -->\n'.format(self.specified_comment[1]))
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self.test_data.write('</{}>\n'.format(self.specified_doctype))
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self.test_data.seek(0)
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# Data received from handlers - to be validated
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self.version = None
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self.encoding = None
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self.standalone = None
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self.doctype = None
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self.publicID = None
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self.systemID = None
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self.end_of_dtd = False
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self.comments = []
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def test_handlers(self):
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class TestLexicalHandler(LexicalHandler):
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def __init__(self, test_harness, *args, **kwargs):
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super().__init__(*args, **kwargs)
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self.test_harness = test_harness
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def startDTD(self, doctype, publicID, systemID):
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self.test_harness.doctype = doctype
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self.test_harness.publicID = publicID
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self.test_harness.systemID = systemID
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def endDTD(self):
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self.test_harness.end_of_dtd = True
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def comment(self, text):
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self.test_harness.comments.append(text)
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self.parser = create_parser()
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self.parser.setContentHandler(ContentHandler())
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self.parser.setProperty(
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'http://xml.org/sax/properties/lexical-handler',
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TestLexicalHandler(self))
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source = InputSource()
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source.setCharacterStream(self.test_data)
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self.parser.parse(source)
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self.assertEqual(self.doctype, self.specified_doctype)
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self.assertIsNone(self.publicID)
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self.assertIsNone(self.systemID)
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self.assertTrue(self.end_of_dtd)
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self.assertEqual(len(self.comments),
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len(self.specified_comment))
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self.assertEqual(f' {self.specified_comment[0]} ', self.comments[0])
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class CDATAHandlerTest(unittest.TestCase):
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def setUp(self):
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self.parser = None
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self.specified_chars = []
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self.specified_chars.append(('Parseable character data', False))
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self.specified_chars.append(('<> &% - assorted other XML junk.', True))
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self.char_index = 0 # Used to index specified results within handlers
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self.test_data = StringIO()
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self.test_data.write('<root_doc>\n')
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self.test_data.write('<some_pcdata>\n')
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self.test_data.write(f'{self.specified_chars[0][0]}\n')
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self.test_data.write('</some_pcdata>\n')
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self.test_data.write('<some_cdata>\n')
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self.test_data.write(f'<![CDATA[{self.specified_chars[1][0]}]]>\n')
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self.test_data.write('</some_cdata>\n')
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self.test_data.write('</root_doc>\n')
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self.test_data.seek(0)
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# Data received from handlers - to be validated
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self.chardata = []
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self.in_cdata = False
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def test_handlers(self):
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class TestLexicalHandler(LexicalHandler):
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def __init__(self, test_harness, *args, **kwargs):
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super().__init__(*args, **kwargs)
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self.test_harness = test_harness
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def startCDATA(self):
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self.test_harness.in_cdata = True
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def endCDATA(self):
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self.test_harness.in_cdata = False
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class TestCharHandler(ContentHandler):
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def __init__(self, test_harness, *args, **kwargs):
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super().__init__(*args, **kwargs)
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self.test_harness = test_harness
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def characters(self, content):
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if content != '\n':
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h = self.test_harness
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t = h.specified_chars[h.char_index]
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h.assertEqual(t[0], content)
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h.assertEqual(t[1], h.in_cdata)
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h.char_index += 1
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self.parser = create_parser()
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self.parser.setContentHandler(TestCharHandler(self))
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self.parser.setProperty(
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'http://xml.org/sax/properties/lexical-handler',
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TestLexicalHandler(self))
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source = InputSource()
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source.setCharacterStream(self.test_data)
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self.parser.parse(source)
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self.assertFalse(self.in_cdata)
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self.assertEqual(self.char_index, 2)
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def test_main():
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run_unittest(MakeParserTest,
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ParseTest,
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@ -1368,7 +1518,10 @@ def test_main():
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StreamReaderWriterXmlgenTest,
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ExpatReaderTest,
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ErrorReportingTest,
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XmlReaderTest)
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XmlReaderTest,
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LexicalHandlerTest,
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CDATAHandlerTest)
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if __name__ == "__main__":
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test_main()
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@ -340,3 +340,48 @@ all_properties = [property_lexical_handler,
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property_xml_string,
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property_encoding,
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property_interning_dict]
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class LexicalHandler:
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"""Optional SAX2 handler for lexical events.
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This handler is used to obtain lexical information about an XML
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document, that is, information about how the document was encoded
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(as opposed to what it contains, which is reported to the
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ContentHandler), such as comments and CDATA marked section
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boundaries.
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To set the LexicalHandler of an XMLReader, use the setProperty
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method with the property identifier
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'http://xml.org/sax/properties/lexical-handler'."""
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def comment(self, content):
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"""Reports a comment anywhere in the document (including the
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DTD and outside the document element).
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content is a string that holds the contents of the comment."""
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def startDTD(self, name, public_id, system_id):
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"""Report the start of the DTD declarations, if the document
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has an associated DTD.
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A startEntity event will be reported before declaration events
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from the external DTD subset are reported, and this can be
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used to infer from which subset DTD declarations derive.
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name is the name of the document element type, public_id the
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public identifier of the DTD (or None if none were supplied)
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and system_id the system identfier of the external subset (or
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None if none were supplied)."""
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def endDTD(self):
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"""Signals the end of DTD declarations."""
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def startCDATA(self):
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"""Reports the beginning of a CDATA marked section.
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The contents of the CDATA marked section will be reported
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through the characters event."""
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def endCDATA(self):
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"""Reports the end of a CDATA marked section."""
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@ -0,0 +1,2 @@
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Add the :class:`xml.sax.handler.LexicalHandler` class that is present in
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other SAX XML implementations.
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