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245 lines
8.4 KiB
245 lines
8.4 KiB
5 months ago
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#
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# ElementTree
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# $Id: ElementInclude.py 1862 2004-06-18 07:31:02Z Fredrik $
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#
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# limited xinclude support for element trees
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#
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# history:
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# 2003-08-15 fl created
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# 2003-11-14 fl fixed default loader
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#
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# Copyright (c) 2003-2004 by Fredrik Lundh. All rights reserved.
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#
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# fredrik@pythonware.com
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# http://www.pythonware.com
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#
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# --------------------------------------------------------------------
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# The ElementTree toolkit is
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#
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# Copyright (c) 1999-2004 by Fredrik Lundh
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#
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# By obtaining, using, and/or copying this software and/or its
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# associated documentation, you agree that you have read, understood,
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# and will comply with the following terms and conditions:
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#
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# Permission to use, copy, modify, and distribute this software and
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# its associated documentation for any purpose and without fee is
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# hereby granted, provided that the above copyright notice appears in
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# all copies, and that both that copyright notice and this permission
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# notice appear in supporting documentation, and that the name of
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# Secret Labs AB or the author not be used in advertising or publicity
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# pertaining to distribution of the software without specific, written
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# prior permission.
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#
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# SECRET LABS AB AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH REGARD
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# TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANT-
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# ABILITY AND FITNESS. IN NO EVENT SHALL SECRET LABS AB OR THE AUTHOR
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# BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY
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# DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
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# WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
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# ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
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# OF THIS SOFTWARE.
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# --------------------------------------------------------------------
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"""
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Limited XInclude support for the ElementTree package.
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While lxml.etree has full support for XInclude (see
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`etree.ElementTree.xinclude()`), this module provides a simpler, pure
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Python, ElementTree compatible implementation that supports a simple
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form of custom URL resolvers.
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"""
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from lxml import etree
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try:
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from urlparse import urljoin
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from urllib2 import urlopen
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except ImportError:
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# Python 3
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from urllib.parse import urljoin
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from urllib.request import urlopen
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XINCLUDE = "{http://www.w3.org/2001/XInclude}"
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XINCLUDE_INCLUDE = XINCLUDE + "include"
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XINCLUDE_FALLBACK = XINCLUDE + "fallback"
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XINCLUDE_ITER_TAG = XINCLUDE + "*"
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# For security reasons, the inclusion depth is limited to this read-only value by default.
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DEFAULT_MAX_INCLUSION_DEPTH = 6
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##
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# Fatal include error.
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class FatalIncludeError(etree.LxmlSyntaxError):
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pass
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class LimitedRecursiveIncludeError(FatalIncludeError):
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pass
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##
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# ET compatible default loader.
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# This loader reads an included resource from disk.
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#
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# @param href Resource reference.
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# @param parse Parse mode. Either "xml" or "text".
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# @param encoding Optional text encoding.
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# @return The expanded resource. If the parse mode is "xml", this
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# is an ElementTree instance. If the parse mode is "text", this
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# is a Unicode string. If the loader fails, it can return None
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# or raise an IOError exception.
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# @throws IOError If the loader fails to load the resource.
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def default_loader(href, parse, encoding=None):
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file = open(href, 'rb')
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if parse == "xml":
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data = etree.parse(file).getroot()
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else:
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data = file.read()
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if not encoding:
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encoding = 'utf-8'
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data = data.decode(encoding)
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file.close()
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return data
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##
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# Default loader used by lxml.etree - handles custom resolvers properly
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#
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def _lxml_default_loader(href, parse, encoding=None, parser=None):
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if parse == "xml":
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data = etree.parse(href, parser).getroot()
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else:
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if "://" in href:
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f = urlopen(href)
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else:
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f = open(href, 'rb')
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data = f.read()
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f.close()
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if not encoding:
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encoding = 'utf-8'
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data = data.decode(encoding)
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return data
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##
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# Wrapper for ET compatibility - drops the parser
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def _wrap_et_loader(loader):
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def load(href, parse, encoding=None, parser=None):
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return loader(href, parse, encoding)
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return load
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##
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# Expand XInclude directives.
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#
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# @param elem Root element.
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# @param loader Optional resource loader. If omitted, it defaults
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# to {@link default_loader}. If given, it should be a callable
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# that implements the same interface as <b>default_loader</b>.
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# @param base_url The base URL of the original file, to resolve
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# relative include file references.
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# @param max_depth The maximum number of recursive inclusions.
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# Limited to reduce the risk of malicious content explosion.
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# Pass None to disable the limitation.
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# @throws LimitedRecursiveIncludeError If the {@link max_depth} was exceeded.
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# @throws FatalIncludeError If the function fails to include a given
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# resource, or if the tree contains malformed XInclude elements.
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# @throws IOError If the function fails to load a given resource.
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# @returns the node or its replacement if it was an XInclude node
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def include(elem, loader=None, base_url=None,
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max_depth=DEFAULT_MAX_INCLUSION_DEPTH):
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if max_depth is None:
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max_depth = -1
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elif max_depth < 0:
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raise ValueError("expected non-negative depth or None for 'max_depth', got %r" % max_depth)
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if base_url is None:
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if hasattr(elem, 'getroot'):
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tree = elem
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elem = elem.getroot()
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else:
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tree = elem.getroottree()
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if hasattr(tree, 'docinfo'):
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base_url = tree.docinfo.URL
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elif hasattr(elem, 'getroot'):
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elem = elem.getroot()
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_include(elem, loader, base_url, max_depth)
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def _include(elem, loader=None, base_url=None,
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max_depth=DEFAULT_MAX_INCLUSION_DEPTH, _parent_hrefs=None):
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if loader is not None:
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load_include = _wrap_et_loader(loader)
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else:
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load_include = _lxml_default_loader
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if _parent_hrefs is None:
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_parent_hrefs = set()
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parser = elem.getroottree().parser
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include_elements = list(
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elem.iter(XINCLUDE_ITER_TAG))
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for e in include_elements:
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if e.tag == XINCLUDE_INCLUDE:
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# process xinclude directive
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href = urljoin(base_url, e.get("href"))
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parse = e.get("parse", "xml")
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parent = e.getparent()
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if parse == "xml":
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if href in _parent_hrefs:
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raise FatalIncludeError(
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"recursive include of %r detected" % href
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)
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if max_depth == 0:
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raise LimitedRecursiveIncludeError(
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"maximum xinclude depth reached when including file %s" % href)
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node = load_include(href, parse, parser=parser)
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if node is None:
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raise FatalIncludeError(
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"cannot load %r as %r" % (href, parse)
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)
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node = _include(node, loader, href, max_depth - 1, {href} | _parent_hrefs)
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if e.tail:
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node.tail = (node.tail or "") + e.tail
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if parent is None:
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return node # replaced the root node!
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parent.replace(e, node)
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elif parse == "text":
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text = load_include(href, parse, encoding=e.get("encoding"))
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if text is None:
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raise FatalIncludeError(
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"cannot load %r as %r" % (href, parse)
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)
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predecessor = e.getprevious()
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if predecessor is not None:
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predecessor.tail = (predecessor.tail or "") + text
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elif parent is None:
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return text # replaced the root node!
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else:
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parent.text = (parent.text or "") + text + (e.tail or "")
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parent.remove(e)
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else:
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raise FatalIncludeError(
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"unknown parse type in xi:include tag (%r)" % parse
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)
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elif e.tag == XINCLUDE_FALLBACK:
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parent = e.getparent()
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if parent is not None and parent.tag != XINCLUDE_INCLUDE:
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raise FatalIncludeError(
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"xi:fallback tag must be child of xi:include (%r)" % e.tag
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)
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else:
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raise FatalIncludeError(
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"Invalid element found in XInclude namespace (%r)" % e.tag
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)
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return elem
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