130 lines
4.3 KiB
Python
130 lines
4.3 KiB
Python
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import datetime
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import re
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from collections import namedtuple
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from django.db.models.fields.related import RECURSIVE_RELATIONSHIP_CONSTANT
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FieldReference = namedtuple("FieldReference", "to through")
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COMPILED_REGEX_TYPE = type(re.compile(""))
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class RegexObject:
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def __init__(self, obj):
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self.pattern = obj.pattern
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self.flags = obj.flags
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def __eq__(self, other):
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if not isinstance(other, RegexObject):
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return NotImplemented
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return self.pattern == other.pattern and self.flags == other.flags
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def get_migration_name_timestamp():
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return datetime.datetime.now().strftime("%Y%m%d_%H%M")
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def resolve_relation(model, app_label=None, model_name=None):
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"""
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Turn a model class or model reference string and return a model tuple.
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app_label and model_name are used to resolve the scope of recursive and
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unscoped model relationship.
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"""
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if isinstance(model, str):
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if model == RECURSIVE_RELATIONSHIP_CONSTANT:
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if app_label is None or model_name is None:
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raise TypeError(
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"app_label and model_name must be provided to resolve "
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"recursive relationships."
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)
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return app_label, model_name
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if "." in model:
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app_label, model_name = model.split(".", 1)
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return app_label, model_name.lower()
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if app_label is None:
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raise TypeError(
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"app_label must be provided to resolve unscoped model relationships."
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)
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return app_label, model.lower()
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return model._meta.app_label, model._meta.model_name
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def field_references(
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model_tuple,
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field,
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reference_model_tuple,
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reference_field_name=None,
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reference_field=None,
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):
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"""
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Return either False or a FieldReference if `field` references provided
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context.
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False positives can be returned if `reference_field_name` is provided
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without `reference_field` because of the introspection limitation it
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incurs. This should not be an issue when this function is used to determine
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whether or not an optimization can take place.
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"""
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remote_field = field.remote_field
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if not remote_field:
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return False
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references_to = None
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references_through = None
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if resolve_relation(remote_field.model, *model_tuple) == reference_model_tuple:
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to_fields = getattr(field, "to_fields", None)
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if (
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reference_field_name is None
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or
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# Unspecified to_field(s).
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to_fields is None
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or
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# Reference to primary key.
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(
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None in to_fields
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and (reference_field is None or reference_field.primary_key)
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)
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or
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# Reference to field.
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reference_field_name in to_fields
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):
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references_to = (remote_field, to_fields)
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through = getattr(remote_field, "through", None)
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if through and resolve_relation(through, *model_tuple) == reference_model_tuple:
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through_fields = remote_field.through_fields
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if (
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reference_field_name is None
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or
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# Unspecified through_fields.
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through_fields is None
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or
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# Reference to field.
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reference_field_name in through_fields
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):
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references_through = (remote_field, through_fields)
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if not (references_to or references_through):
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return False
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return FieldReference(references_to, references_through)
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def get_references(state, model_tuple, field_tuple=()):
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"""
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Generator of (model_state, name, field, reference) referencing
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provided context.
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If field_tuple is provided only references to this particular field of
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model_tuple will be generated.
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"""
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for state_model_tuple, model_state in state.models.items():
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for name, field in model_state.fields.items():
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reference = field_references(
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state_model_tuple, field, model_tuple, *field_tuple
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)
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if reference:
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yield model_state, name, field, reference
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def field_is_referenced(state, model_tuple, field_tuple):
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"""Return whether `field_tuple` is referenced by any state models."""
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return next(get_references(state, model_tuple, field_tuple), None) is not None
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