Package lxml :: Module ElementInclude |
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# Source Code for Module lxml.ElementInclude

      1  #
      2  # ElementTree
      3  # $Id: ElementInclude.py 1862 2004-06-18 07:31:02Z Fredrik $
      4  #
      5  # limited xinclude support for element trees
      6  #
      7  # history:
      8  # 2003-08-15 fl   created
      9  # 2003-11-14 fl   fixed default loader
     10  #
     11  # Copyright (c) 2003-2004 by Fredrik Lundh.  All rights reserved.
     12  #
     13  # fredrik@pythonware.com
     14  # http://www.pythonware.com
     15  #
     16  # --------------------------------------------------------------------
     17  # The ElementTree toolkit is
     18  #
     19  # Copyright (c) 1999-2004 by Fredrik Lundh
     20  #
     21  # By obtaining, using, and/or copying this software and/or its
     22  # associated documentation, you agree that you have read, understood,
     23  # and will comply with the following terms and conditions:
     24  #
     25  # Permission to use, copy, modify, and distribute this software and
     26  # its associated documentation for any purpose and without fee is
     27  # hereby granted, provided that the above copyright notice appears in
     28  # all copies, and that both that copyright notice and this permission
     29  # notice appear in supporting documentation, and that the name of
     30  # Secret Labs AB or the author not be used in advertising or publicity
     31  # pertaining to distribution of the software without specific, written
     32  # prior permission.
     33  #
     34  # SECRET LABS AB AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH REGARD
     35  # TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANT-
     36  # ABILITY AND FITNESS.  IN NO EVENT SHALL SECRET LABS AB OR THE AUTHOR
     37  # BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY
     38  # DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
     39  # WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
     40  # ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
     41  # OF THIS SOFTWARE.
     42  # --------------------------------------------------------------------
     43
     44  """
     45  Limited XInclude support for the ElementTree package.
     46
     47  While lxml.etree has full support for XInclude (see
     48  `etree.ElementTree.xinclude()`), this module provides a simpler, pure
     49  Python, ElementTree compatible implementation that supports a simple
     50  form of custom URL resolvers.
     51  """
     52
     53  from lxml import etree
     54  try:
     55      from urlparse import urljoin
     56      from urllib2 import urlopen
     57  except ImportError:
     58      # Python 3
     59      from urllib.parse import urljoin
     60      from urllib.request import urlopen
     61
     62  XINCLUDE = "{http://www.w3.org/2001/XInclude}"
     63
     64  XINCLUDE_INCLUDE = XINCLUDE + "include"
     65  XINCLUDE_FALLBACK = XINCLUDE + "fallback"
     66  XINCLUDE_ITER_TAG = XINCLUDE + "*"
     67
     68  ##
     69  # Fatal include error.
     70
     71 -class FatalIncludeError(etree.LxmlSyntaxError):
     72      pass
     73
     74  ##
     75  # ET compatible default loader.
     76  # This loader reads an included resource from disk.
     77  #
     78  # @param href Resource reference.
     79  # @param parse Parse mode.  Either "xml" or "text".
     80  # @param encoding Optional text encoding.
     81  # @return The expanded resource.  If the parse mode is "xml", this
     82  #    is an ElementTree instance.  If the parse mode is "text", this
     83  #    is a Unicode string.  If the loader fails, it can return None
     84  #    or raise an IOError exception.
     85  # @throws IOError If the loader fails to load the resource.
     86
     87 -def default_loader(href, parse, encoding=None):
     88      file = open(href, 'rb')
     89      if parse == "xml":
     90          data = etree.parse(file).getroot()
     91      else:
     92          data = file.read()
     93          if not encoding:
     94              encoding = 'utf-8'
     95          data = data.decode(encoding)
     96      file.close()
     97      return data
     98
     99  ##
    100  # Default loader used by lxml.etree - handles custom resolvers properly
    101  #
    102
    103 -def _lxml_default_loader(href, parse, encoding=None, parser=None):
    104      if parse == "xml":
    105          data = etree.parse(href, parser).getroot()
    106      else:
    107          if "://" in href:
    108              f = urlopen(href)
    109          else:
    110              f = open(href, 'rb')
    111          data = f.read()
    112          f.close()
    113          if not encoding:
    114              encoding = 'utf-8'
    115          data = data.decode(encoding)
    116      return data
    117
    118  ##
    119  # Wrapper for ET compatibility - drops the parser
    120
    121 -def _wrap_et_loader(loader):
    122      def load(href, parse, encoding=None, parser=None):
    123          return loader(href, parse, encoding)
    124      return load
    125
    126
    127  ##
    128  # Expand XInclude directives.
    129  #
    130  # @param elem Root element.
    131  # @param loader Optional resource loader.  If omitted, it defaults
    132  #     to {@link default_loader}.  If given, it should be a callable
    133  #     that implements the same interface as <b>default_loader</b>.
    134  # @throws FatalIncludeError If the function fails to include a given
    135  #     resource, or if the tree contains malformed XInclude elements.
    136  # @throws IOError If the function fails to load a given resource.
    137  # @returns the node or its replacement if it was an XInclude node
    138
    139 -def include(elem, loader=None, base_url=None):
    140      if base_url is None:
    141          if hasattr(elem, 'getroot'):
    142              tree = elem
    143              elem = elem.getroot()
    144          else:
    145              tree = elem.getroottree()
    146          if hasattr(tree, 'docinfo'):
    147              base_url = tree.docinfo.URL
    148      elif hasattr(elem, 'getroot'):
    149          elem = elem.getroot()
    150      _include(elem, loader, base_url=base_url)
    151
    152 -def _include(elem, loader=None, _parent_hrefs=None, base_url=None):
    153      if loader is not None:
    154          load_include = _wrap_et_loader(loader)
    155      else:
    156          load_include = _lxml_default_loader
    157
    158      if _parent_hrefs is None:
    159          _parent_hrefs = set()
    160
    161      parser = elem.getroottree().parser
    162
    163      include_elements = list(
    164          elem.iter(XINCLUDE_ITER_TAG))
    165
    166      for e in include_elements:
    167          if e.tag == XINCLUDE_INCLUDE:
    168              # process xinclude directive
    169              href = urljoin(base_url, e.get("href"))
    170              parse = e.get("parse", "xml")
    171              parent = e.getparent()
    172              if parse == "xml":
    173                  if href in _parent_hrefs:
    174                      raise FatalIncludeError(
    175                          "recursive include of %r detected" % href
    176                          )
    177                  _parent_hrefs.add(href)
    178                  node = load_include(href, parse, parser=parser)
    179                  if node is None:
    180                      raise FatalIncludeError(
    181                          "cannot load %r as %r" % (href, parse)
    182                          )
    183                  node = _include(node, loader, _parent_hrefs)
    184                  if e.tail:
    185                      node.tail = (node.tail or "") + e.tail
    186                  if parent is None:
    187                      return node # replaced the root node!
    188                  parent.replace(e, node)
    189              elif parse == "text":
    190                  text = load_include(href, parse, encoding=e.get("encoding"))
    191                  if text is None:
    192                      raise FatalIncludeError(
    193                          "cannot load %r as %r" % (href, parse)
    194                          )
    195                  predecessor = e.getprevious()
    196                  if predecessor is not None:
    197                      predecessor.tail = (predecessor.tail or "") + text
    198                  elif parent is None:
    199                      return text # replaced the root node!
    200                  else:
    201                      parent.text = (parent.text or "") + text + (e.tail or "")
    202                  parent.remove(e)
    203              else:
    204                  raise FatalIncludeError(
    205                      "unknown parse type in xi:include tag (%r)" % parse
    206                  )
    207          elif e.tag == XINCLUDE_FALLBACK:
    208              parent = e.getparent()
    209              if parent is not None and parent.tag != XINCLUDE_INCLUDE:
    210                  raise FatalIncludeError(
    211                      "xi:fallback tag must be child of xi:include (%r)" % e.tag
    212                      )
    213          else:
    214              raise FatalIncludeError(
    215                  "Invalid element found in XInclude namespace (%r)" % e.tag
    216                  )
    217      return elem
    218