add EmbeddedModelField

Author: timgraham

.pre-commit-config.yaml

@@ -44,7 +44,7 @@ repos:
   hooks:
   - id: rstcheck
     additional_dependencies: [sphinx]
-    args: ["--ignore-directives=fieldlookup,setting", "--ignore-roles=lookup,setting"]
+    args: ["--ignore-directives=django-admin,fieldlookup,setting", "--ignore-roles=djadmin,lookup,setting"]
 
 # We use the Python version instead of the original version which seems to require Docker
 # https://github.com/koalaman/shellcheck-precommit

THIRD-PARTY-NOTICES

@@ -3,7 +3,7 @@ be distributed under licenses different than this software.
 
 The attached notices are provided for information only.
 
-django-mongodb-backend began by borrowing code from Django non-rel's
+django-mongodb-backend and EmbeddedModelField began by borrowing code from
 django-mongodb-engine (https://github.com/django-nonrel/mongodb-engine),
 abandoned since 2015 and Django 1.6.
 

django_mongodb_backend/compiler.py

@@ -741,7 +741,7 @@ def execute_sql(self, result_type):
             elif hasattr(value, "prepare_database_save"):
                 if field.remote_field:
                     value = value.prepare_database_save(field)
-                else:
+                elif not hasattr(field, "embedded_model"):
                     raise TypeError(
                         f"Tried to update field {field} with a model "
                         f"instance, {value!r}. Use a value compatible with "

django_mongodb_backend/fields/__init__.py

@@ -1,10 +1,17 @@
 from .array import ArrayField
 from .auto import ObjectIdAutoField
 from .duration import register_duration_field
+from .embedded_model import EmbeddedModelField
 from .json import register_json_field
 from .objectid import ObjectIdField
 
-__all__ = ["register_fields", "ArrayField", "ObjectIdAutoField", "ObjectIdField"]
+__all__ = [
+    "register_fields",
+    "ArrayField",
+    "EmbeddedModelField",
+    "ObjectIdAutoField",
+    "ObjectIdField",
+]
 
 
 def register_fields():

django_mongodb_backend/fields/embedded_model.py

@@ -0,0 +1,161 @@
+from django.core import checks
+from django.db import models
+from django.db.models.fields.related import lazy_related_operation
+from django.db.models.lookups import Transform
+
+from .. import forms
+
+
+class EmbeddedModelField(models.Field):
+    """Field that stores a model instance."""
+
+    def __init__(self, embedded_model, *args, **kwargs):
+        """
+        `embedded_model` is the model class of the instance to be stored.
+        Like other relational fields, it may also be passed as a string.
+        """
+        self.embedded_model = embedded_model
+        super().__init__(*args, **kwargs)
+
+    def check(self, **kwargs):
+        errors = super().check(**kwargs)
+        for field in self.embedded_model._meta.fields:
+            if field.remote_field:
+                errors.append(
+                    checks.Error(
+                        "Embedded models cannot have relational fields "
+                        f"({self.embedded_model().__class__.__name__}.{field.name} "
+                        f"is a {field.__class__.__name__}).",
+                        obj=self,
+                        id="django_mongodb.embedded_model.E001",
+                    )
+                )
+        return errors
+
+    def deconstruct(self):
+        name, path, args, kwargs = super().deconstruct()
+        if path.startswith("django_mongodb_backend.fields.embedded_model"):
+            path = path.replace(
+                "django_mongodb_backend.fields.embedded_model", "django_mongodb_backend.fields"
+            )
+        kwargs["embedded_model"] = self.embedded_model
+        return name, path, args, kwargs
+
+    def get_internal_type(self):
+        return "EmbeddedModelField"
+
+    def _set_model(self, model):
+        """
+        Resolve embedded model class once the field knows the model it belongs
+        to. If __init__()'s embedded_model argument is a string, resolve it to
+        the actual model class, similar to relation fields.
+        """
+        self._model = model
+        if model is not None and isinstance(self.embedded_model, str):
+
+            def _resolve_lookup(_, resolved_model):
+                self.embedded_model = resolved_model
+
+            lazy_related_operation(_resolve_lookup, model, self.embedded_model)
+
+    model = property(lambda self: self._model, _set_model)
+
+    def from_db_value(self, value, expression, connection):
+        return self.to_python(value)
+
+    def to_python(self, value):
+        """
+        Pass embedded model fields' values through each field's to_python() and
+        reinstantiate the embedded instance.
+        """
+        if value is None:
+            return None
+        if not isinstance(value, dict):
+            return value
+        instance = self.embedded_model(
+            **{
+                field.attname: field.to_python(value[field.attname])
+                for field in self.embedded_model._meta.fields
+                if field.attname in value
+            }
+        )
+        instance._state.adding = False
+        return instance
+
+    def get_db_prep_save(self, embedded_instance, connection):
+        """
+        Apply pre_save() and get_db_prep_save() of embedded instance fields and
+        create the {field: value} dict to be saved.
+        """
+        if embedded_instance is None:
+            return None
+        if not isinstance(embedded_instance, self.embedded_model):
+            raise TypeError(
+                f"Expected instance of type {self.embedded_model!r}, not "
+                f"{type(embedded_instance)!r}."
+            )
+        field_values = {}
+        add = embedded_instance._state.adding
+        for field in embedded_instance._meta.fields:
+            value = field.get_db_prep_save(
+                field.pre_save(embedded_instance, add), connection=connection
+            )
+            # Exclude unset primary keys (e.g. {'id': None}).
+            if field.primary_key and value is None:
+                continue
+            field_values[field.attname] = value
+        # This instance will exist in the database soon.
+        embedded_instance._state.adding = False
+        return field_values
+
+    def get_transform(self, name):
+        transform = super().get_transform(name)
+        if transform:
+            return transform
+        return KeyTransformFactory(name)
+
+    def validate(self, value, model_instance):
+        super().validate(value, model_instance)
+        if self.embedded_model is None:
+            return
+        for field in self.embedded_model._meta.fields:
+            attname = field.attname
+            field.validate(getattr(value, attname), model_instance)
+
+    def formfield(self, **kwargs):
+        return super().formfield(
+            **{
+                "form_class": forms.EmbeddedModelField,
+                "model": self.embedded_model,
+                "prefix": self.name,
+                **kwargs,
+            }
+        )
+
+
+class KeyTransform(Transform):
+    def __init__(self, key_name, *args, **kwargs):
+        super().__init__(*args, **kwargs)
+        self.key_name = str(key_name)
+
+    def preprocess_lhs(self, compiler, connection):
+        key_transforms = [self.key_name]
+        previous = self.lhs
+        while isinstance(previous, KeyTransform):
+            key_transforms.insert(0, previous.key_name)
+            previous = previous.lhs
+        mql = previous.as_mql(compiler, connection)
+        return mql, key_transforms
+
+    def as_mql(self, compiler, connection):
+        mql, key_transforms = self.preprocess_lhs(compiler, connection)
+        transforms = ".".join(key_transforms)
+        return f"{mql}.{transforms}"
+
+
+class KeyTransformFactory:
+    def __init__(self, key_name):
+        self.key_name = key_name
+
+    def __call__(self, *args, **kwargs):
+        return KeyTransform(self.key_name, *args, **kwargs)

django_mongodb_backend/forms/__init__.py

@@ -1,6 +1,13 @@
-from .fields import ObjectIdField, SimpleArrayField, SplitArrayField, SplitArrayWidget
+from .fields import (
+    EmbeddedModelField,
+    ObjectIdField,
+    SimpleArrayField,
+    SplitArrayField,
+    SplitArrayWidget,
+)
 
 __all__ = [
+    "EmbeddedModelField",
     "SimpleArrayField",
     "SplitArrayField",
     "SplitArrayWidget",

django_mongodb_backend/forms/fields/__init__.py

@@ -1,7 +1,9 @@
 from .array import SimpleArrayField, SplitArrayField, SplitArrayWidget
+from .embedded_model import EmbeddedModelField
 from .objectid import ObjectIdField
 
 __all__ = [
+    "EmbeddedModelField",
     "SimpleArrayField",
     "SplitArrayField",
     "SplitArrayWidget",

django_mongodb_backend/forms/fields/embedded_model.py

@@ -0,0 +1,62 @@
+from django import forms
+from django.forms.models import modelform_factory
+from django.utils.safestring import mark_safe
+from django.utils.translation import gettext_lazy as _
+
+
+class EmbeddedModelWidget(forms.MultiWidget):
+    def __init__(self, field_names, *args, **kwargs):
+        self.field_names = field_names
+        super().__init__(*args, **kwargs)
+        # The default widget names are "_0", "_1", etc. Use the field names
+        # instead since that's how they'll be rendered by the model form.
+        self.widgets_names = ["-" + name for name in field_names]
+
+    def decompress(self, value):
+        if value is None:
+            return []
+        # Get the data from `value` (a model) for each field.
+        return [getattr(value, name) for name in self.field_names]
+
+
+class EmbeddedModelBoundField(forms.BoundField):
+    def __str__(self):
+        """Render the model form as the representation for this field."""
+        form = self.field.model_form_cls(instance=self.value(), **self.field.form_kwargs)
+        return mark_safe(f"{form.as_div()}")  # noqa: S308
+
+
+class EmbeddedModelField(forms.MultiValueField):
+    default_error_messages = {
+        "invalid": _("Enter a list of values."),
+        "incomplete": _("Enter all required values."),
+    }
+
+    def __init__(self, model, prefix, *args, **kwargs):
+        form_kwargs = {}
+        # To avoid collisions with other fields on the form, each subfield must
+        # be prefixed with the name of the field.
+        form_kwargs["prefix"] = prefix
+        self.form_kwargs = form_kwargs
+        self.model_form_cls = modelform_factory(model, fields="__all__")
+        self.model_form = self.model_form_cls(**form_kwargs)
+        self.field_names = list(self.model_form.fields.keys())
+        fields = self.model_form.fields.values()
+        widgets = [field.widget for field in fields]
+        widget = EmbeddedModelWidget(self.field_names, widgets)
+        super().__init__(*args, fields=fields, widget=widget, require_all_fields=False, **kwargs)
+
+    def compress(self, data_dict):
+        if not data_dict:
+            return None
+        values = dict(zip(self.field_names, data_dict, strict=False))
+        return self.model_form._meta.model(**values)
+
+    def get_bound_field(self, form, field_name):
+        return EmbeddedModelBoundField(form, self, field_name)
+
+    def bound_data(self, data, initial):
+        if self.disabled:
+            return initial
+        # Transform the bound data into a model instance.
+        return self.compress(data)