Source code for marshmallow_sqlalchemy.convert

import functools
import inspect
import uuid

import marshmallow as ma
import sqlalchemy as sa
from marshmallow import fields, validate
from sqlalchemy.dialects import mssql, mysql, postgresql
from sqlalchemy.orm import SynonymProperty

from .exceptions import ModelConversionError
from .fields import Related, RelatedList

def _is_field(value):
    return isinstance(value, type) and issubclass(value, fields.Field)

def _base_column(column):
    """Unwrap proxied columns"""
    if column not in column.base_columns and len(column.base_columns) == 1:
        [base] = column.base_columns
        return base
    return column

def _has_default(column):
    return (
        column.default is not None
        or column.server_default is not None
        or _is_auto_increment(column)

def _is_auto_increment(column):
    return column.table is not None and column is column.table._autoincrement_column

def _postgres_array_factory(converter, data_type):
    return functools.partial(
        fields.List, converter._get_field_class_for_data_type(data_type.item_type)

def _field_update_kwargs(field_class, field_kwargs, kwargs):
    if not kwargs:
        return field_kwargs

    if isinstance(field_class, functools.partial):
        # Unwrap partials, assuming that they bind a Field to arguments
        field_class = field_class.func

    possible_field_keywords = {
        for cls in inspect.getmro(field_class)
        for key, param in inspect.signature(cls).parameters.items()
        if param.kind is inspect.Parameter.POSITIONAL_OR_KEYWORD
        or param.kind is inspect.Parameter.KEYWORD_ONLY
    for k, v in kwargs.items():
        if k in possible_field_keywords:
            field_kwargs[k] = v
            field_kwargs["metadata"][k] = v
    return field_kwargs

[docs] class ModelConverter: """Class that converts a SQLAlchemy model into a dictionary of corresponding marshmallow `Fields <marshmallow.fields.Field>`. """ SQLA_TYPE_MAPPING = { sa.Enum: fields.Field, sa.JSON: fields.Raw, postgresql.BIT: fields.Integer, postgresql.OID: fields.Integer, postgresql.UUID: fields.UUID, postgresql.MACADDR: fields.String, postgresql.INET: fields.String, postgresql.CIDR: fields.String, postgresql.JSON: fields.Raw, postgresql.JSONB: fields.Raw, postgresql.HSTORE: fields.Raw, postgresql.ARRAY: _postgres_array_factory, postgresql.MONEY: fields.Decimal, postgresql.DATE: fields.Date, postgresql.TIME: fields.Time, mysql.BIT: fields.Integer, mysql.YEAR: fields.Integer, mysql.SET: fields.List, mysql.ENUM: fields.Field, mysql.INTEGER: fields.Integer, mysql.DATETIME: fields.DateTime, mssql.BIT: fields.Integer, mssql.UNIQUEIDENTIFIER: fields.UUID, } DIRECTION_MAPPING = {"MANYTOONE": False, "MANYTOMANY": True, "ONETOMANY": True} def __init__(self, schema_cls=None): self.schema_cls = schema_cls @property def type_mapping(self): if self.schema_cls: return self.schema_cls.TYPE_MAPPING else: return ma.Schema.TYPE_MAPPING def fields_for_model( self, model, *, include_fk=False, include_relationships=False, fields=None, exclude=None, base_fields=None, dict_cls=dict, ): result = dict_cls() base_fields = base_fields or {} for prop in model.__mapper__.attrs: key = self._get_field_name(prop) if self._should_exclude_field(prop, fields=fields, exclude=exclude): # Allow marshmallow to validate and exclude the field key. result[key] = None continue if isinstance(prop, SynonymProperty): continue if hasattr(prop, "columns"): if not include_fk: # Only skip a column if there is no overriden column # which does not have a Foreign Key. for column in prop.columns: if not column.foreign_keys: break else: continue if not include_relationships and hasattr(prop, "direction"): continue field = base_fields.get(key) or self.property2field(prop) if field: result[key] = field return result def fields_for_table( self, table, *, include_fk=False, fields=None, exclude=None, base_fields=None, dict_cls=dict, ): result = dict_cls() base_fields = base_fields or {} for column in table.columns: key = self._get_field_name(column) if self._should_exclude_field(column, fields=fields, exclude=exclude): # Allow marshmallow to validate and exclude the field key. result[key] = None continue if not include_fk and column.foreign_keys: continue # Overridden fields are specified relative to key generated by # self._get_key_for_column(...), rather than keys in source model field = base_fields.get(key) or self.column2field(column) if field: result[key] = field return result def property2field(self, prop, *, instance=True, field_class=None, **kwargs): # handle synonyms # Attribute renamed "_proxied_object" in 1.4 for attr in ("_proxied_property", "_proxied_object"): proxied_obj = getattr(prop, attr, None) if proxied_obj is not None: prop = proxied_obj field_class = field_class or self._get_field_class_for_property(prop) if not instance: return field_class field_kwargs = self._get_field_kwargs_for_property(prop) _field_update_kwargs(field_class, field_kwargs, kwargs) ret = field_class(**field_kwargs) if ( hasattr(prop, "direction") and self.DIRECTION_MAPPING[] and prop.uselist is True ): related_list_kwargs = _field_update_kwargs( RelatedList, self.get_base_kwargs(), kwargs ) ret = RelatedList(ret, **related_list_kwargs) return ret def column2field(self, column, *, instance=True, **kwargs): field_class = self._get_field_class_for_column(column) if not instance: return field_class field_kwargs = self.get_base_kwargs() self._add_column_kwargs(field_kwargs, column) _field_update_kwargs(field_class, field_kwargs, kwargs) return field_class(**field_kwargs) def field_for(self, model, property_name, **kwargs): target_model = model prop_name = property_name attr = getattr(model, property_name) remote_with_local_multiplicity = False if hasattr(attr, "remote_attr"): target_model = attr.target_class prop_name = attr.value_attr remote_with_local_multiplicity = attr.local_attr.prop.uselist prop = target_model.__mapper__.attrs.get(prop_name) converted_prop = self.property2field(prop, **kwargs) if remote_with_local_multiplicity: related_list_kwargs = _field_update_kwargs( RelatedList, self.get_base_kwargs(), kwargs ) return RelatedList(converted_prop, **related_list_kwargs) else: return converted_prop def _get_field_name(self, prop_or_column): return prop_or_column.key def _get_field_class_for_column(self, column): return self._get_field_class_for_data_type(column.type) def _get_field_class_for_data_type(self, data_type): field_cls = None types = inspect.getmro(type(data_type)) # First search for a field class from self.SQLA_TYPE_MAPPING for col_type in types: if col_type in self.SQLA_TYPE_MAPPING: field_cls = self.SQLA_TYPE_MAPPING[col_type] if callable(field_cls) and not _is_field(field_cls): field_cls = field_cls(self, data_type) break else: # Try to find a field class based on the column's python_type try: python_type = data_type.python_type except NotImplementedError: python_type = None if python_type in self.type_mapping: field_cls = self.type_mapping[python_type] else: if hasattr(data_type, "impl"): return self._get_field_class_for_data_type(data_type.impl) raise ModelConversionError( f"Could not find field column of type {types[0]}." ) return field_cls def _get_field_class_for_property(self, prop): if hasattr(prop, "direction"): field_cls = Related else: column = _base_column(prop.columns[0]) field_cls = self._get_field_class_for_column(column) return field_cls def _merge_validators(self, defaults, new): new_classes = [validator.__class__ for validator in new] return [ validator for validator in defaults if validator.__class__ not in new_classes ] + new def _get_field_kwargs_for_property(self, prop): kwargs = self.get_base_kwargs() if hasattr(prop, "columns"): column = _base_column(prop.columns[0]) self._add_column_kwargs(kwargs, column) prop = column if hasattr(prop, "direction"): # Relationship property self._add_relationship_kwargs(kwargs, prop) if getattr(prop, "doc", None): # Useful for documentation generation kwargs["metadata"]["description"] = prop.doc return kwargs def _add_column_kwargs(self, kwargs, column): """Add keyword arguments to kwargs (in-place) based on the passed in `Column <sqlalchemy.schema.Column>`. """ if hasattr(column, "nullable"): if column.nullable: kwargs["allow_none"] = True kwargs["required"] = not column.nullable and not _has_default(column) # If there is no nullable attribute, we are dealing with a property # that does not derive from the Column class. Mark as dump_only. else: kwargs["dump_only"] = True if hasattr(column.type, "enums") and not kwargs.get("dump_only"): kwargs["validate"].append(validate.OneOf(choices=column.type.enums)) # Add a length validator if a max length is set on the column # Skip UUID columns # (see if hasattr(column.type, "length") and not kwargs.get("dump_only"): column_length = column.type.length if column_length is not None: try: python_type = column.type.python_type except (AttributeError, NotImplementedError): python_type = None if not python_type or not issubclass(python_type, uuid.UUID): kwargs["validate"].append(validate.Length(max=column_length)) if getattr(column.type, "asdecimal", False): kwargs["places"] = getattr(column.type, "scale", None) def _add_relationship_kwargs(self, kwargs, prop): """Add keyword arguments to kwargs (in-place) based on the passed in relationship `Property`. """ nullable = True for pair in prop.local_remote_pairs: if not pair[0].nullable: if prop.uselist is True: nullable = False break kwargs.update({"allow_none": nullable, "required": not nullable}) def _should_exclude_field(self, column, fields=None, exclude=None): key = self._get_field_name(column) if fields and key not in fields: return True if exclude and key in exclude: return True return False def get_base_kwargs(self): return {"validate": [], "metadata": {}}
default_converter = ModelConverter() fields_for_model = default_converter.fields_for_model """Generate a dict of field_name: `marshmallow.fields.Field` pairs for the given model. Note: SynonymProperties are ignored. Use an explicit field if you want to include a synonym. :param model: The SQLAlchemy model :param bool include_fk: Whether to include foreign key fields in the output. :param bool include_relationships: Whether to include relationships fields in the output. :return: dict of field_name: Field instance pairs """ property2field = default_converter.property2field """Convert a SQLAlchemy `Property` to a field instance or class. :param Property prop: SQLAlchemy Property. :param bool instance: If `True`, return `Field` instance, computing relevant kwargs from the given property. If `False`, return the `Field` class. :param kwargs: Additional keyword arguments to pass to the field constructor. :return: A `marshmallow.fields.Field` class or instance. """ column2field = default_converter.column2field """Convert a SQLAlchemy `Column <sqlalchemy.schema.Column>` to a field instance or class. :param sqlalchemy.schema.Column column: SQLAlchemy Column. :param bool instance: If `True`, return `Field` instance, computing relevant kwargs from the given property. If `False`, return the `Field` class. :return: A `marshmallow.fields.Field` class or instance. """ field_for = default_converter.field_for """Convert a property for a mapped SQLAlchemy class to a marshmallow `Field`. Example: :: date_created = field_for(Author, 'date_created', dump_only=True) author = field_for(Book, 'author') :param type model: A SQLAlchemy mapped class. :param str property_name: The name of the property to convert. :param kwargs: Extra keyword arguments to pass to `property2field` :return: A `marshmallow.fields.Field` class or instance. """