155 lines
5.6 KiB
Python
155 lines
5.6 KiB
Python
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"""A collection of modules for iterating through different kinds of
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tree, generating tokens identical to those produced by the tokenizer
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module.
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To create a tree walker for a new type of tree, you need to
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implement a tree walker object (called TreeWalker by convention) that
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implements a 'serialize' method which takes a tree as sole argument and
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returns an iterator which generates tokens.
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"""
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from __future__ import absolute_import, division, unicode_literals
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from .. import constants
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from .._utils import default_etree
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__all__ = ["getTreeWalker", "pprint"]
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treeWalkerCache = {}
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def getTreeWalker(treeType, implementation=None, **kwargs):
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"""Get a TreeWalker class for various types of tree with built-in support
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:arg str treeType: the name of the tree type required (case-insensitive).
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Supported values are:
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* "dom": The xml.dom.minidom DOM implementation
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* "etree": A generic walker for tree implementations exposing an
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elementtree-like interface (known to work with ElementTree,
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cElementTree and lxml.etree).
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* "lxml": Optimized walker for lxml.etree
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* "genshi": a Genshi stream
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:arg implementation: A module implementing the tree type e.g.
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xml.etree.ElementTree or cElementTree (Currently applies to the "etree"
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tree type only).
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:arg kwargs: keyword arguments passed to the etree walker--for other
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walkers, this has no effect
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:returns: a TreeWalker class
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"""
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treeType = treeType.lower()
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if treeType not in treeWalkerCache:
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if treeType == "dom":
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from . import dom
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treeWalkerCache[treeType] = dom.TreeWalker
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elif treeType == "genshi":
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from . import genshi
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treeWalkerCache[treeType] = genshi.TreeWalker
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elif treeType == "lxml":
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from . import etree_lxml
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treeWalkerCache[treeType] = etree_lxml.TreeWalker
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elif treeType == "etree":
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from . import etree
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if implementation is None:
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implementation = default_etree
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# XXX: NEVER cache here, caching is done in the etree submodule
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return etree.getETreeModule(implementation, **kwargs).TreeWalker
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return treeWalkerCache.get(treeType)
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def concatenateCharacterTokens(tokens):
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pendingCharacters = []
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for token in tokens:
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type = token["type"]
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if type in ("Characters", "SpaceCharacters"):
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pendingCharacters.append(token["data"])
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else:
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if pendingCharacters:
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yield {"type": "Characters", "data": "".join(pendingCharacters)}
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pendingCharacters = []
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yield token
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if pendingCharacters:
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yield {"type": "Characters", "data": "".join(pendingCharacters)}
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def pprint(walker):
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"""Pretty printer for tree walkers
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Takes a TreeWalker instance and pretty prints the output of walking the tree.
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:arg walker: a TreeWalker instance
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"""
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output = []
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indent = 0
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for token in concatenateCharacterTokens(walker):
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type = token["type"]
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if type in ("StartTag", "EmptyTag"):
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# tag name
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if token["namespace"] and token["namespace"] != constants.namespaces["html"]:
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if token["namespace"] in constants.prefixes:
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ns = constants.prefixes[token["namespace"]]
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else:
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ns = token["namespace"]
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name = "%s %s" % (ns, token["name"])
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else:
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name = token["name"]
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output.append("%s<%s>" % (" " * indent, name))
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indent += 2
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# attributes (sorted for consistent ordering)
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attrs = token["data"]
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for (namespace, localname), value in sorted(attrs.items()):
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if namespace:
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if namespace in constants.prefixes:
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ns = constants.prefixes[namespace]
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else:
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ns = namespace
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name = "%s %s" % (ns, localname)
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else:
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name = localname
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output.append("%s%s=\"%s\"" % (" " * indent, name, value))
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# self-closing
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if type == "EmptyTag":
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indent -= 2
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elif type == "EndTag":
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indent -= 2
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elif type == "Comment":
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output.append("%s<!-- %s -->" % (" " * indent, token["data"]))
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elif type == "Doctype":
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if token["name"]:
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if token["publicId"]:
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output.append("""%s<!DOCTYPE %s "%s" "%s">""" %
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(" " * indent,
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token["name"],
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token["publicId"],
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token["systemId"] if token["systemId"] else ""))
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elif token["systemId"]:
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output.append("""%s<!DOCTYPE %s "" "%s">""" %
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(" " * indent,
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token["name"],
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token["systemId"]))
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else:
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output.append("%s<!DOCTYPE %s>" % (" " * indent,
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token["name"]))
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else:
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output.append("%s<!DOCTYPE >" % (" " * indent,))
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elif type == "Characters":
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output.append("%s\"%s\"" % (" " * indent, token["data"]))
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elif type == "SpaceCharacters":
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assert False, "concatenateCharacterTokens should have got rid of all Space tokens"
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else:
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raise ValueError("Unknown token type, %s" % type)
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return "\n".join(output)
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