src/mdis/walker.py

   1 __all__ = [
   2     "Walker",
   3     "WalkerMeta",
   4 ]
   5
   6 import enum
   7 import dataclasses
   8
   9 from . import dispatcher
  10
  11
  12 class WalkerMeta(dispatcher.DispatcherMeta):
  13     pass
  14
  15
  16 class PartId(enum.Enum):
  17     Index = enum.auto()
  18     Attribute = enum.auto()
  19     Hash = enum.auto()
  20
  21     def __call__(self, part):
  22         return {
  23             PartId.Index: "[{part}]",
  24             PartId.Attribute: ".{part}",
  25             PartId.Hash: "{{{part}}}",
  26         }[self].format(part=part)
  27
  28
  29 class Walker(dispatcher.Dispatcher, metaclass=WalkerMeta):
  30     @dispatcher.Hook(tuple, list)
  31     def dispatch_ordered_sequence(self, instance):
  32         for (index, item) in enumerate(instance):
  33             yield (item, instance, index, PartId.Index)
  34             yield from self(item)
  35
  36     @dispatcher.Hook(set, frozenset)
  37     def dispatch_unordered_sequence(self, instance):
  38         for item in instance:
  39             yield (item, instance, item, PartId.Hash)
  40             yield from self(item)
  41
  42     @dispatcher.Hook(dataclasses.is_dataclass)
  43     def dispatch_dataclass(self, instance):
  44         for field in dataclasses.fields(instance):
  45             key = field.name
  46             value = getattr(instance, key)
  47             yield (value, instance, key, PartId.Attribute)
  48             yield from self(value)
  49
  50     @dispatcher.Hook(dict)
  51     def dispatch_mapping(self, instance):
  52         for (key, value) in instance.items():
  53             yield (key, instance, key, PartId.Hash)
  54             yield from self(key)
  55             yield (value, instance, key, PartId.Index)
  56             yield from self(value)
  57
  58     @dispatcher.Hook(object)
  59     def dispatch_object(self, instance, path=()):
  60         yield from ()