This method overrides django.db.models.fields.files.FileField.deconstruct.
* The name of the field on the model, if contribute_to_class() has been run. * The import path of the field, including the class:e.g. django.db.models.IntegerField This should be the most portable version, so less specific may be better. * A list of positional arguments. * A dict of keyword arguments. Note that the positional or keyword arguments must contain values of the following types (including inner values of collection types): * None, bool, str, int, float, complex, set, frozenset, list, tuple, dict * UUID * datetime.datetime (naive), datetime.date * top-level classes, top-level functions - will be referenced by their full import path * Storage instances - these have their own deconstruct() method This is because the values here must be serialized into a text format (possibly new Python code, possibly JSON) and these are the only types with encoding handlers defined. There's no need to return the exact way the field was instantiated this time, just ensure that the resulting field is the same - prefer keyword arguments over positional ones, and omit parameters with their default values.
This method is hooked up to model's post_init signal to update dimensions after instantiating a model instance. However, dimensions won't be updated if the dimensions fields are already populated. This avoids unnecessary recalculation when loading an object from the database. Dimensions can be forced to update with force=True, which is how ImageFileDescriptor.__set__ calls this method.