Skip introspection on defined fields. #57
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Some SQLAlchemy columns can't currently be introspected by marshmallow-sqlalchemy, or can't be introspected in principle. For example, columns defined using mapped SQL expressions (using `column_property` or `object_session`) don't have types and don't define a `nullable` attribute. In these rare cases, users may want to set custom fields in their schemas. But this isn't currently possible, since we raise a `ModelConversionError` when we encounter a column we can't introspect. This patch skips introspection when the user has explicitly defined a field in the schema. Alternatively, we could map `NullType` to `Raw` in `SQLA_TYPE_MAPPING` and handle properties that don't define `nullable`, which would allow users to work with mapped expressions without schema field overrides. I slightly prefer this approach, since it's a bit more flexible, and because I don't think it's a bad thing for users to explicitly define types of mapped expressions.
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This looks like the right approach. Thanks. |
sloria
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Feb 22, 2016
Skip introspection on defined fields.
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Some SQLAlchemy columns can't currently be introspected by
marshmallow-sqlalchemy, or can't be introspected in principle. For
example, columns defined using mapped SQL expressions (using
column_propertyorobject_session) don't have types and don't definea
nullableattribute. In these rare cases, users may want to setcustom fields in their schemas. But this isn't currently possible, since
we raise a
ModelConversionErrorwhen we encounter a column we can'tintrospect. This patch skips introspection when the user has explicitly
defined a field in the schema.
Alternatively, we could map
NullTypetoRawinSQLA_TYPE_MAPPINGand handle properties that don't define
nullable, which would allowusers to work with mapped expressions without schema field overrides. I
slightly prefer this approach, since it's a bit more flexible, and
because I don't think it's a bad thing for users to explicitly define
types of mapped expressions.
Probably too much discussion for a rare edge case. Thoughts @sloria?