|
| 1 | +import contextlib |
| 2 | + |
| 3 | +from django.core import checks |
| 4 | +from django.core.exceptions import FieldDoesNotExist, ValidationError |
| 5 | +from django.db import connections, models |
| 6 | +from django.db.models.fields.related import lazy_related_operation |
| 7 | + |
| 8 | +from .embedded_model import KeyTransformFactory |
| 9 | + |
| 10 | + |
| 11 | +class PolymorphicEmbeddedModelField(models.Field): |
| 12 | + """Field that stores a model instance of varying type.""" |
| 13 | + |
| 14 | + stores_model_instance = True |
| 15 | + |
| 16 | + def __init__(self, embedded_models, *args, **kwargs): |
| 17 | + """ |
| 18 | + `embedded_models` is a list of possible model classes to be stored. |
| 19 | + Like other relational fields, each model may also be passed as a |
| 20 | + string. |
| 21 | + """ |
| 22 | + self.embedded_models = embedded_models |
| 23 | + kwargs["editable"] = False |
| 24 | + super().__init__(*args, **kwargs) |
| 25 | + |
| 26 | + def db_type(self, connection): |
| 27 | + return "embeddedDocuments" |
| 28 | + |
| 29 | + def check(self, **kwargs): |
| 30 | + from ..models import EmbeddedModel |
| 31 | + |
| 32 | + errors = super().check(**kwargs) |
| 33 | + embedded_fields = {} |
| 34 | + for model in self.embedded_models: |
| 35 | + if not issubclass(model, EmbeddedModel): |
| 36 | + return [ |
| 37 | + checks.Error( |
| 38 | + "Embedded models must be a subclass of " |
| 39 | + "django_mongodb_backend.models.EmbeddedModel.", |
| 40 | + obj=self, |
| 41 | + hint="{model} doesn't subclass EmbeddedModel.", |
| 42 | + id="django_mongodb_backend.embedded_model.E002", |
| 43 | + ) |
| 44 | + ] |
| 45 | + for field in model._meta.fields: |
| 46 | + if field.remote_field: |
| 47 | + errors.append( |
| 48 | + checks.Error( |
| 49 | + "Embedded models cannot have relational fields " |
| 50 | + f"({model().__class__.__name__}.{field.name} " |
| 51 | + f"is a {field.__class__.__name__}).", |
| 52 | + obj=self, |
| 53 | + id="django_mongodb_backend.embedded_model.E001", |
| 54 | + ) |
| 55 | + ) |
| 56 | + field_name = field.name |
| 57 | + if existing_field := embedded_fields.get(field.name): |
| 58 | + connection = _get_mongodb_connection() |
| 59 | + if existing_field.db_type(connection) != field.db_type(connection): |
| 60 | + errors.append( |
| 61 | + checks.Warning( |
| 62 | + f"Embedded models {existing_field.model._meta.label} " |
| 63 | + f"and {field.model._meta.label} both have field " |
| 64 | + f"'{field_name}' of different type.", |
| 65 | + obj=self, |
| 66 | + id="django_mongodb_backend.embedded_model.E003", |
| 67 | + hint="It may be impossible to query both fields.", |
| 68 | + ) |
| 69 | + ) |
| 70 | + |
| 71 | + else: |
| 72 | + embedded_fields[field_name] = field |
| 73 | + return errors |
| 74 | + |
| 75 | + def deconstruct(self): |
| 76 | + name, path, args, kwargs = super().deconstruct() |
| 77 | + if path.startswith("django_mongodb_backend.fields.polymorphic_embedded_model"): |
| 78 | + path = path.replace( |
| 79 | + "django_mongodb_backend.fields.polymorphic_embedded_model", |
| 80 | + "django_mongodb_backend.fields", |
| 81 | + ) |
| 82 | + kwargs["embedded_models"] = self.embedded_models |
| 83 | + del kwargs["editable"] |
| 84 | + return name, path, args, kwargs |
| 85 | + |
| 86 | + def get_internal_type(self): |
| 87 | + return "PolymorphicEmbeddedModelField" |
| 88 | + |
| 89 | + def _set_model(self, model): |
| 90 | + """ |
| 91 | + Resolve embedded model classes once the field knows the model it |
| 92 | + belongs to. If any of the items in __init__()'s embedded_models |
| 93 | + argument are strings, resolve each to the actual model class, similar |
| 94 | + to relational fields. |
| 95 | + """ |
| 96 | + self._model = model |
| 97 | + if model is not None: |
| 98 | + for embedded_model in self.embedded_models: |
| 99 | + if isinstance(embedded_model, str): |
| 100 | + |
| 101 | + def _resolve_lookup(_, *resolved_models): |
| 102 | + self.embedded_models = resolved_models |
| 103 | + |
| 104 | + lazy_related_operation(_resolve_lookup, model, *self.embedded_models) |
| 105 | + |
| 106 | + model = property(lambda self: self._model, _set_model) |
| 107 | + |
| 108 | + def from_db_value(self, value, expression, connection): |
| 109 | + return self.to_python(value) |
| 110 | + |
| 111 | + def to_python(self, value): |
| 112 | + """ |
| 113 | + Pass embedded model fields' values through each field's to_python() and |
| 114 | + reinstantiate the embedded instance. |
| 115 | + """ |
| 116 | + if value is None: |
| 117 | + return None |
| 118 | + if not isinstance(value, dict): |
| 119 | + return value |
| 120 | + model_class = self._get_model_from_label(value.pop("_label")) |
| 121 | + instance = model_class( |
| 122 | + **{ |
| 123 | + field.attname: field.to_python(value[field.attname]) |
| 124 | + for field in model_class._meta.fields |
| 125 | + if field.attname in value |
| 126 | + } |
| 127 | + ) |
| 128 | + instance._state.adding = False |
| 129 | + return instance |
| 130 | + |
| 131 | + def get_db_prep_save(self, embedded_instance, connection): |
| 132 | + """ |
| 133 | + Apply pre_save() and get_db_prep_save() of embedded instance fields and |
| 134 | + create the {field: value} dict to be saved. |
| 135 | + """ |
| 136 | + if embedded_instance is None: |
| 137 | + return None |
| 138 | + if not isinstance(embedded_instance, self.embedded_models): |
| 139 | + raise TypeError( |
| 140 | + f"Expected instance of type {self.embedded_models!r}, not " |
| 141 | + f"{type(embedded_instance)!r}." |
| 142 | + ) |
| 143 | + field_values = {} |
| 144 | + add = embedded_instance._state.adding |
| 145 | + for field in embedded_instance._meta.fields: |
| 146 | + value = field.get_db_prep_save( |
| 147 | + field.pre_save(embedded_instance, add), connection=connection |
| 148 | + ) |
| 149 | + # Exclude unset primary keys (e.g. {'id': None}). |
| 150 | + if field.primary_key and value is None: |
| 151 | + continue |
| 152 | + field_values[field.attname] = value |
| 153 | + # Store the model's label to know the class to use for initializing |
| 154 | + # upon retrieval. |
| 155 | + field_values["_label"] = embedded_instance._meta.label |
| 156 | + # This instance will exist in the database soon. |
| 157 | + embedded_instance._state.adding = False |
| 158 | + return field_values |
| 159 | + |
| 160 | + def get_transform(self, name): |
| 161 | + transform = super().get_transform(name) |
| 162 | + if transform: |
| 163 | + return transform |
| 164 | + for model in self.embedded_models: |
| 165 | + with contextlib.suppress(FieldDoesNotExist): |
| 166 | + field = model._meta.get_field(name) |
| 167 | + break |
| 168 | + else: |
| 169 | + raise FieldDoesNotExist( |
| 170 | + f"The models of field '{self.name}' have no field named '{name}'." |
| 171 | + ) |
| 172 | + return KeyTransformFactory(name, field) |
| 173 | + |
| 174 | + def validate(self, value, model_instance): |
| 175 | + super().validate(value, model_instance) |
| 176 | + if not isinstance(value, self.embedded_models): |
| 177 | + raise ValidationError( |
| 178 | + f"Expected instance of type {self.embedded_models!r}, not {type(value)!r}." |
| 179 | + ) |
| 180 | + for field in value._meta.fields: |
| 181 | + attname = field.attname |
| 182 | + field.validate(getattr(value, attname), model_instance) |
| 183 | + |
| 184 | + def formfield(self, **kwargs): |
| 185 | + raise NotImplementedError("PolymorphicEmbeddedModelField does not support forms.") |
| 186 | + |
| 187 | + def _get_model_from_label(self, label): |
| 188 | + return next(model for model in self.embedded_models if model._meta.label == label) |
| 189 | + |
| 190 | + |
| 191 | +def _get_mongodb_connection(): |
| 192 | + for alias in connections: |
| 193 | + if connections[alias].vendor == "mongodb": |
| 194 | + return connections[alias] |
| 195 | + return None |
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