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Field-level validation errors cannot be saved on a nested field with many=True #298

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nelfin opened this Issue Oct 14, 2015 · 0 comments

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nelfin commented Oct 14, 2015

When validating a field, all of its error messages are saved and appended to the list of messages for that field name in call_and_store, but for fields.Nested with many=True the error messages for child elements of the collection are saved and stored in a dictionary keyed by the element index. This causes the following exception on this minimal test case:

class Inner(Schema):
    req = fields.Field(required=True)

class Outer(Schema):
    inner = fields.Nested(Inner, many=True)

    @validates('inner')
    def validates_inner(self, data):
        raise ValidationError('not a chance')

outer = Outer()
_, errors = outer.load({'inner': [{}]})
Traceback (most recent call last):
  File "/home/andrew/misc/marshmallow/tests/test_schema.py", line 1238, in test_all_errors_on_many_nested_field_with_validates_decorator
    _, errors = outer.load({'inner': [{}]})
  File "/home/andrew/misc/marshmallow/marshmallow/schema.py", line 539, in load
    result, errors = self._do_load(data, many, partial=partial, postprocess=True)
  File "/home/andrew/misc/marshmallow/marshmallow/schema.py", line 610, in _do_load
    self._invoke_field_validators(data=result, many=many)
  File "/home/andrew/misc/marshmallow/marshmallow/schema.py", line 789, in _invoke_field_validators
    field_obj=field_obj
  File "/home/andrew/misc/marshmallow/marshmallow/marshalling.py", line 74, in call_and_store
    errors.setdefault(field_name, []).extend(err.messages)
AttributeError: 'dict' object has no attribute 'extend'

nelfin added a commit to nelfin/marshmallow that referenced this issue Oct 14, 2015

Fix error messages on many Nested fields
Fixes marshmallow-code#298. When validating a field, all of its error messages are saved
and appended to the list of messages for that field name in
call_and_store, but for fields.Nested with many=True the error messages
for child elements of the collection are saved and stored in a
dictionary keyed by the element index.

This change introduces a _field key to the errors dictionary of a Nested
field for validation errors raised about the field as a whole, rather
than any one element. For example:

    >>> from marshmallow import (
    ...     fields, validates, Schema, ValidationError,
    ... )
    >>> class Inner(Schema):
    ...     x = fields.Int()
    ...
    >>> class Outer(Schema):
    ...     inner = fields.Nested(Inner, many=True)
    ...
    ...     @validates('inner')
    ...     def check_length(self, data):
    ...         if len(data) < 3:
    ...             raise ValidationError('Not enough elements.')
    ...
    >>> o = Outer()
    >>> _, errors = o.load({'inner': [{'x': 123}, {'x': 'abc'}]})
    >>> errors  # doctest: +NORMALIZE_WHITESPACE
    {'inner': {1: {'x': ['Not a valid integer.']},
              '_field': ['Not enough elements.']}}

@sloria sloria added the bug label Oct 14, 2015

@sloria sloria closed this Oct 15, 2015

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