lib/yaml/resolver.py

   1
   2 __all__ = ['BaseResolver', 'Resolver']
   3
   4 from error import *
   5 from nodes import *
   6
   7 import re
   8
   9 class ResolverError(YAMLError):
  10     pass
  11
  12 class BaseResolver(object):
  13
  14     DEFAULT_SCALAR_TAG = u'tag:yaml.org,2002:str'
  15     DEFAULT_SEQUENCE_TAG = u'tag:yaml.org,2002:seq'
  16     DEFAULT_MAPPING_TAG = u'tag:yaml.org,2002:map'
  17
  18     yaml_implicit_resolvers = {}
  19     yaml_path_resolvers = {}
  20
  21     def __init__(self):
  22         self.resolver_exact_paths = []
  23         self.resolver_prefix_paths = []
  24
  25     def add_implicit_resolver(cls, tag, regexp, first):
  26         if not 'yaml_implicit_resolvers' in cls.__dict__:
  27             cls.yaml_implicit_resolvers = cls.yaml_implicit_resolvers.copy()
  28         if first is None:
  29             first = [None]
  30         for ch in first:
  31             cls.yaml_implicit_resolvers.setdefault(ch, []).append((tag, regexp))
  32     add_implicit_resolver = classmethod(add_implicit_resolver)
  33
  34     def add_path_resolver(cls, tag, path, kind=None):
  35         if not 'yaml_path_resolvers' in cls.__dict__:
  36             cls.yaml_path_resolvers = cls.yaml_path_resolvers.copy()
  37         new_path = []
  38         for element in path:
  39             if isinstance(element, (list, tuple)):
  40                 if len(element) == 2:
  41                     node_check, index_check = element
  42                 elif len(element) == 1:
  43                     node_check = element[0]
  44                     index_check = True
  45                 else:
  46                     raise ResolverError("Invalid path element: %s" % element)
  47             else:
  48                 node_check = None
  49                 index_check = element
  50             if node_check is str:
  51                 node_check = ScalarNode
  52             elif node_check is list:
  53                 node_check = SequenceNode
  54             elif node_check is dict:
  55                 node_check = MappingNode
  56             elif node_check not in [ScalarNode, SequenceNode, MappingNode]  \
  57                     and not isinstance(node_check, basestring)  \
  58                     and node_check is not None:
  59                 raise ResolverError("Invalid node checker: %s" % node_check)
  60             if not isinstance(index_check, (basestring, int))   \
  61                     and index_check is not None:
  62                 raise ResolverError("Invalid index checker: %s" % index_check)
  63             new_path.append((node_check, index_check))
  64         if kind is str:
  65             kind = ScalarNode
  66         elif kind is list:
  67             kind = SequenceNode
  68         elif kind is dict:
  69             kind = MappingNode
  70         elif kind not in [ScalarNode, SequenceNode, MappingNode]    \
  71                 and kind is not None:
  72             raise ResolverError("Invalid node kind: %s" % kind)
  73         cls.yaml_path_resolvers[tuple(new_path), kind] = tag
  74     add_path_resolver = classmethod(add_path_resolver)
  75
  76     def descend_resolver(self, current_node, current_index):
  77         exact_paths = {}
  78         prefix_paths = []
  79         if current_node:
  80             depth = len(self.resolver_prefix_paths)
  81             for path, kind in self.resolver_prefix_paths[-1]:
  82                 if self.check_resolver_prefix(depth, path, kind,
  83                         current_node, current_index):
  84                     if len(path) > depth:
  85                         prefix_paths.append((path, kind))
  86                     else:
  87                         exact_paths[kind] = self.yaml_path_resolvers[path, kind]
  88         else:
  89             for path, kind in self.yaml_path_resolvers:
  90                 if not path:
  91                     exact_paths[kind] = self.yaml_path_resolvers[path, kind]
  92                 else:
  93                     prefix_paths.append((path, kind))
  94         self.resolver_exact_paths.append(exact_paths)
  95         self.resolver_prefix_paths.append(prefix_paths)
  96
  97     def ascend_resolver(self):
  98         self.resolver_exact_paths.pop()
  99         self.resolver_prefix_paths.pop()
 100
 101     def check_resolver_prefix(self, depth, path, kind,
 102             current_node, current_index):
 103         node_check, index_check = path[depth-1]
 104         if isinstance(node_check, basestring):
 105             if current_node.tag != node_check:
 106                 return
 107         elif node_check is not None:
 108             if not isinstance(current_node, node_check):
 109                 return
 110         if index_check is True and current_index is not None:
 111             return
 112         if index_check in [False, None] and current_index is None:
 113             return
 114         if isinstance(index_check, basestring):
 115             if not (isinstance(current_index, ScalarNode)
 116                     and index_check == current_index.value):
 117                 return
 118         elif isinstance(index_check, int):
 119             if index_check != current_index:
 120                 return
 121         return True
 122
 123     def resolve(self, kind, value, implicit):
 124         if kind is ScalarNode and implicit[0]:
 125             if value == u'':
 126                 resolvers = self.yaml_implicit_resolvers.get(u'', [])
 127             else:
 128                 resolvers = self.yaml_implicit_resolvers.get(value[0], [])
 129             resolvers += self.yaml_implicit_resolvers.get(None, [])
 130             for tag, regexp in resolvers:
 131                 if regexp.match(value):
 132                     return tag
 133             implicit = implicit[1]
 134         exact_paths = self.resolver_exact_paths[-1]
 135         if kind in exact_paths:
 136             return exact_paths[kind]
 137         if None in exact_paths:
 138             return exact_paths[None]
 139         if kind is ScalarNode:
 140             return self.DEFAULT_SCALAR_TAG
 141         elif kind is SequenceNode:
 142             return self.DEFAULT_SEQUENCE_TAG
 143         elif kind is MappingNode:
 144             return self.DEFAULT_MAPPING_TAG
 145
 146 class Resolver(BaseResolver):
 147     pass
 148
 149 Resolver.add_implicit_resolver(
 150         u'tag:yaml.org,2002:bool',
 151         re.compile(ur'''^(?:yes|Yes|YES|n|N|no|No|NO
 152                     |true|True|TRUE|false|False|FALSE
 153                     |on|On|ON|off|Off|OFF)$''', re.X),
 154         list(u'yYnNtTfFoO'))
 155
 156 Resolver.add_implicit_resolver(
 157         u'tag:yaml.org,2002:float',
 158         re.compile(ur'''^(?:[-+]?(?:[0-9][0-9_]*)?\.[0-9_]*(?:[eE][-+][0-9]+)?
 159                     |[-+]?[0-9][0-9_]*(?::[0-5]?[0-9])+\.[0-9_]*
 160                     |[-+]?\.(?:inf|Inf|INF)
 161                     |\.(?:nan|NaN|NAN))$''', re.X),
 162         list(u'-+0123456789.'))
 163
 164 Resolver.add_implicit_resolver(
 165         u'tag:yaml.org,2002:int',
 166         re.compile(ur'''^(?:[-+]?0b[0-1_]+
 167                     |[-+]?0[0-7_]+
 168                     |[-+]?(?:0|[1-9][0-9_]*)
 169                     |[-+]?0x[0-9a-fA-F_]+
 170                     |[-+]?[1-9][0-9_]*(?::[0-5]?[0-9])+)$''', re.X),
 171         list(u'-+0123456789'))
 172
 173 Resolver.add_implicit_resolver(
 174         u'tag:yaml.org,2002:merge',
 175         re.compile(ur'^(?:<<)$'),
 176         ['<'])
 177
 178 Resolver.add_implicit_resolver(
 179         u'tag:yaml.org,2002:null',
 180         re.compile(ur'''^(?: ~
 181                     |null|Null|NULL
 182                     | )$''', re.X),
 183         [u'~', u'n', u'N', u''])
 184
 185 Resolver.add_implicit_resolver(
 186         u'tag:yaml.org,2002:timestamp',
 187         re.compile(ur'''^(?:[0-9][0-9][0-9][0-9]-[0-9][0-9]-[0-9][0-9]
 188                     |[0-9][0-9][0-9][0-9] -[0-9][0-9]? -[0-9][0-9]?
 189                      (?:[Tt]|[ \t]+)[0-9][0-9]?
 190                      :[0-9][0-9] :[0-9][0-9] (?:\.[0-9]*)?
 191                      (?:[ \t]*(?:Z|[-+][0-9][0-9]?(?::[0-9][0-9])?))?)$''', re.X),
 192         list(u'0123456789'))
 193
 194 Resolver.add_implicit_resolver(
 195         u'tag:yaml.org,2002:value',
 196         re.compile(ur'^(?:=)$'),
 197         ['='])
 198
 199 # The following resolver is only for documentation purposes. It cannot work
 200 # because plain scalars cannot start with '!', '&', or '*'.
 201 Resolver.add_implicit_resolver(
 202         u'tag:yaml.org,2002:yaml',
 203         re.compile(ur'^(?:!|&|\*)$'),
 204         list(u'!&*'))
 205