Class ModelState

django/db/migrations/state.py:737–1021

Represent a Django Model. Don't use the actual Model class as it's not designed to have its options changed - instead, mutate this one and then render it into a Model as required. Note that while you are allowed to mutate .fields, you are not allowed to mutate the Field instanc

class ModelState:
    """
    Represent a Django Model. Don't use the actual Model class as it's not
    designed to have its options changed - instead, mutate this one and then
    render it into a Model as required.

    Note that while you are allowed to mutate .fields, you are not allowed
    to mutate the Field instances inside there themselves - you must instead
    assign new ones, as these are not detached during a clone.
    """

    def __init__(
        self, app_label, name, fields, options=None, bases=None, managers=None
    ):
        self.app_label = app_label
        self.name = name
        self.fields = dict(fields)
        self.options = options or {}
        self.options.setdefault("indexes", [])
        self.options.setdefault("constraints", [])
        self.bases = bases or (models.Model,)
        self.managers = managers or []
        for name, field in self.fields.items():
            # Sanity-check that fields are NOT already bound to a model.
            if hasattr(field, "model"):
                raise ValueError(
                    'ModelState.fields cannot be bound to a model - "%s" is.' % name
                )
            # Ensure that relation fields are NOT referring to a model class.
            if field.is_relation and hasattr(field.related_model, "_meta"):
                raise ValueError(
                    'Model fields in "ModelState.fields" cannot refer to a model class '
                    f'- "{self.app_label}.{self.name}.{name}.to" does. Use a string '
                    "reference instead."
                )
            if field.many_to_many and hasattr(field.remote_field.through, "_meta"):
                raise ValueError(
                    'Model fields in "ModelState.fields" cannot refer to a model class '
                    f'- "{self.app_label}.{self.name}.{name}.through" does. Use a '
                    "string reference instead."
                )
        # Sanity-check that indexes have their name set.
        for index in self.options["indexes"]:
            if not index.name:
                raise ValueError(
                    "Indexes passed to ModelState require a name attribute. "
                    "%r doesn't have one." % index
                )

    @cached_property
    def name_lower(self):
        return self.name.lower()

    def get_field(self, field_name):
        if (
            field_name == "_order"
            and self.options.get("order_with_respect_to") is not None
        ):