deseasion.backend.schemas.base module

class deseasion.backend.schemas.base.BaseSchema(*args, **kwargs)

Bases: SQLAlchemyAutoSchema

This is the base class for all schemas converting Json and SQL Models.

There are multiple cases for schemas:

  • One schema for all CRU operations: then simply put all fields

  • Two schemas for update and retrieval: then make one schema with non-modifiable fields as dump_only in Meta

  • Two schemas for creation and retrieval: then make one schema with non-created fields as dump_only in Meta (can also add write-only fields in load_only)

  • Three schemas for creation, update and retrieval: split creation schema, then make other schema as an update/retrieval shared schema

  • Careful when associating a resource within another, as the update of one could update the other. If a single schema is used to represent both a resource as itself and the same one nested, the id field will be broken (non-writable for the resource as itself, writable for the nesting resource).

Note

  • Fields with foreign keys are not created by default

  • Relationship fields are not created by default

  • FIelds added manually are not required and non-nullable by default

class Meta

Bases: object

load_instance = True
sqla_session = <sqlalchemy.orm.scoping.scoped_session object>
strict = True
get_future_field(data, key)

Return field value (from instance or serialized data).

Parameters:

  • data – serialized data that will update instance

  • key – field name

Returns:

value

opts: SchemaOpts = <marshmallow_sqlalchemy.schema.SQLAlchemyAutoSchemaOpts object>
class deseasion.backend.schemas.base.FieldLookupNested(nested: ~marshmallow.base.SchemaABC | type | str | dict[str, ~marshmallow.fields.Field | type] | ~typing.Callable[[], ~marshmallow.base.SchemaABC | type | dict[str, ~marshmallow.fields.Field | type]], *, dump_default: ~typing.Any = <marshmallow.missing>, default: ~typing.Any = <marshmallow.missing>, only: ~typing.Sequence[str] | ~typing.AbstractSet[str] | None = None, exclude: ~typing.Sequence[str] | ~typing.AbstractSet[str] = (), many: bool = False, unknown: str | None = None, **kwargs)

Bases: Nested

Nested field which will try to load an existing object.

https://github.com/marshmallow-code/marshmallow-sqlalchemy/issues/117

default_error_messages = {'missing': 'Could not find related object {input}.', 'type': 'Invalid input type. Expected a list.'}

Default error messages.

get_instance_or_fail(data)
class deseasion.backend.schemas.base.FieldMethod(spec_field: Field, serialize: str | None = None, deserialize: str | None = None, **kwargs)

Bases: Method

This class represents a field method with an alternative field to use as source for OpenAPI specification.

Parameters:

  • spec_field – alternative field to use as source for openAPI specification

  • serialize – serialization method used

  • deserialize – deserialization method used

class deseasion.backend.schemas.base.FieldPluck(model, field_name, **kwargs)

Bases: Pluck

This class creates a pluck field for a SQL model.

It creates a new schema for this model, only containing the field to pluck.

Parameters:

  • model – SQL model class to pluck

  • field_name – field to pluck

class deseasion.backend.schemas.base.OneOfSchema(*args, many=False, **kwargs)

Bases: OneOfSchema

This class is a wrapper for marshmallow_oneofschema.OneOfSchema.

It adds one feature necessary to this backend:

  • Pass schema constructor args and kwargs to typed schemas

opts: SchemaOpts = <marshmallow.schema.SchemaOpts object>
with_args(schema)

Create a child schema constructor.

Pass *args and **kwargs which were given when building the oneof schema instance.

Parameters:

schema – child schema to prepare

Returns:

child schema constructor

class deseasion.backend.schemas.base.OneOfSchemaWithType(*args, many=False, **kwargs)

Bases: OneOfSchema

This class is a wrapper for marshmallow_oneofschema.OneOfSchema.

It is to be used for schemas needing the type to appear in the openapi specification while being removed upon deserialization. This is typically the case for oneOf creation schemas.

opts: SchemaOpts = <marshmallow.schema.SchemaOpts object>
with_args(schema)

Create a child schema constructor.

Pass *args and **kwargs which were given when building the oneof schema instance.

Parameters:

schema – child schema to prepare

Returns:

child schema constructor

deseasion.backend.schemas.base.constant_enum(value) → type[Enum]

This creates an enum with a single value.

Its use should be limited to schema polymorphism so a type discriminator which is an enumeration of all possible types (children types) is set as only the child type in the child.

Parameters:

value – either a single enum item or any object

Returns:

enumeration class with only value as item

Note

might override a String field as well if the parent class type discriminator field was left open for future appendings, this is generally how schema polymorphism is implemented in OpenAPI 3.0+. In this case, the closed enumeration must be done in the oneOf classes.