247 lines
8.9 KiB
Python
247 lines
8.9 KiB
Python
from collections import MutableMapping
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from xmodule.x_module import XModuleDescriptor
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from lxml import etree
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import copy
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import logging
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from collections import namedtuple
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from fs.errors import ResourceNotFoundError
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import os
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log = logging.getLogger(__name__)
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# TODO (cpennington): This was implemented in an attempt to improve performance,
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# but the actual improvement wasn't measured (and it was implemented late at night).
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# We should check if it hurts, and whether there's a better way of doing lazy loading
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class LazyLoadingDict(MutableMapping):
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"""
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A dictionary object that lazily loads it's contents from a provided
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function on reads (of members that haven't already been set)
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"""
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def __init__(self, loader):
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self._contents = {}
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self._loaded = False
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self._loader = loader
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self._deleted = set()
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def __getitem__(self, name):
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if not (self._loaded or name in self._contents or name in self._deleted):
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self.load()
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return self._contents[name]
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def __setitem__(self, name, value):
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self._contents[name] = value
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self._deleted.discard(name)
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def __delitem__(self, name):
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del self._contents[name]
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self._deleted.add(name)
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def __contains__(self, name):
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self.load()
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return name in self._contents
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def __len__(self):
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self.load()
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return len(self._contents)
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def __iter__(self):
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self.load()
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return iter(self._contents)
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def __repr__(self):
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self.load()
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return repr(self._contents)
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def load(self):
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if self._loaded:
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return
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loaded_contents = self._loader()
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loaded_contents.update(self._contents)
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self._contents = loaded_contents
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self._loaded = True
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_AttrMapBase = namedtuple('_AttrMap', 'metadata_key to_metadata from_metadata')
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class AttrMap(_AttrMapBase):
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"""
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A class that specifies a metadata_key, a function to transform an xml attribute to be placed in that key,
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and to transform that key value
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"""
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def __new__(_cls, metadata_key, to_metadata=lambda x: x, from_metadata=lambda x: x):
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return _AttrMapBase.__new__(_cls, metadata_key, to_metadata, from_metadata)
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class XmlDescriptor(XModuleDescriptor):
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"""
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Mixin class for standardized parsing of from xml
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"""
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# Extension to append to filename paths
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filename_extension = 'xml'
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# The attributes will be removed from the definition xml passed
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# to definition_from_xml, and from the xml returned by definition_to_xml
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metadata_attributes = ('format', 'graceperiod', 'showanswer', 'rerandomize',
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'start', 'due', 'graded', 'name', 'slug')
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# A dictionary mapping xml attribute names to functions of the value
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# that return the metadata key and value
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xml_attribute_map = {
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'graded': AttrMap('graded', lambda val: val == 'true', lambda val: str(val).lower()),
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'name': AttrMap('display_name'),
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}
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@classmethod
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def definition_from_xml(cls, xml_object, system):
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"""
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Return the definition to be passed to the newly created descriptor
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during from_xml
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xml_object: An etree Element
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"""
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raise NotImplementedError("%s does not implement definition_from_xml" % cls.__name__)
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@classmethod
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def clean_metadata_from_xml(cls, xml_object):
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"""
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Remove any attribute named in self.metadata_attributes from the supplied xml_object
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"""
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for attr in cls.metadata_attributes:
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if xml_object.get(attr) is not None:
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del xml_object.attrib[attr]
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@classmethod
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def file_to_xml(cls, file_object):
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"""
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Used when this module wants to parse a file object to xml
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that will be converted to the definition.
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Returns an lxml Element
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"""
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return etree.parse(file_object).getroot()
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@classmethod
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def from_xml(cls, xml_data, system, org=None, course=None):
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"""
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Creates an instance of this descriptor from the supplied xml_data.
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This may be overridden by subclasses
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xml_data: A string of xml that will be translated into data and children for
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this module
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system: An XModuleSystem for interacting with external resources
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org and course are optional strings that will be used in the generated modules
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url identifiers
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"""
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xml_object = etree.fromstring(xml_data)
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def metadata_loader():
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metadata = {}
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for attr in cls.metadata_attributes:
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val = xml_object.get(attr)
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if val is not None:
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attr_map = cls.xml_attribute_map.get(attr, AttrMap(attr))
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metadata[attr_map.metadata_key] = attr_map.to_metadata(val)
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return metadata
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def definition_loader():
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filename = xml_object.get('filename')
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if filename is None:
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definition_xml = copy.deepcopy(xml_object)
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else:
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filepath = cls._format_filepath(xml_object.tag, filename)
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# TODO (cpennington): If the file doesn't exist at the right path,
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# give the class a chance to fix it up. The file will be written out again
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# in the correct format.
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# This should go away once the CMS is online and has imported all current (fall 2012)
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# courses from xml
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if not system.resources_fs.exists(filepath) and hasattr(cls, 'backcompat_paths'):
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candidates = cls.backcompat_paths(filepath)
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for candidate in candidates:
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if system.resources_fs.exists(candidate):
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filepath = candidate
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break
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log.debug('filepath=%s, resources_fs=%s' % (filepath, system.resources_fs))
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try:
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with system.resources_fs.open(filepath) as file:
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definition_xml = cls.file_to_xml(file)
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except (ResourceNotFoundError, etree.XMLSyntaxError):
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log.exception('Unable to load file contents at path %s' % filepath)
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return {'data': 'Error loading file contents at path %s' % filepath}
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cls.clean_metadata_from_xml(definition_xml)
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return cls.definition_from_xml(definition_xml, system)
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return cls(
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system,
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LazyLoadingDict(definition_loader),
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location=['i4x',
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org,
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course,
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xml_object.tag,
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xml_object.get('slug')],
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metadata=LazyLoadingDict(metadata_loader),
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)
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@classmethod
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def _format_filepath(cls, category, name):
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return u'{category}/{name}.{ext}'.format(category=category, name=name, ext=cls.filename_extension)
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def export_to_xml(self, resource_fs):
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"""
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Returns an xml string representing this module, and all modules underneath it.
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May also write required resources out to resource_fs
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Assumes that modules have single parantage (that no module appears twice in the same course),
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and that it is thus safe to nest modules as xml children as appropriate.
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The returned XML should be able to be parsed back into an identical XModuleDescriptor
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using the from_xml method with the same system, org, and course
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resource_fs is a pyfilesystem office (from the fs package)
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"""
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xml_object = self.definition_to_xml(resource_fs)
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self.__class__.clean_metadata_from_xml(xml_object)
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# Put content in a separate file if it's large (has more than 5 descendent tags)
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if len(list(xml_object.iter())) > 5:
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filepath = self.__class__._format_filepath(self.category, self.name)
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resource_fs.makedir(os.path.dirname(filepath), allow_recreate=True)
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with resource_fs.open(filepath, 'w') as file:
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file.write(etree.tostring(xml_object, pretty_print=True))
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for child in xml_object:
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xml_object.remove(child)
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xml_object.set('filename', self.name)
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xml_object.set('slug', self.name)
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xml_object.tag = self.category
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for attr in self.metadata_attributes:
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attr_map = self.xml_attribute_map.get(attr, AttrMap(attr))
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metadata_key = attr_map.metadata_key
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if metadata_key not in self.metadata or metadata_key in self._inherited_metadata:
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continue
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val = attr_map.from_metadata(self.metadata[metadata_key])
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xml_object.set(attr, val)
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return etree.tostring(xml_object, pretty_print=True)
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def definition_to_xml(self, resource_fs):
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"""
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Return a new etree Element object created from this modules definition.
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"""
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raise NotImplementedError("%s does not implement definition_to_xml" % self.__class__.__name__)
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