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OArepo Validate library for record metadata validation

Project description

oarepo-validate

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OArepo Validate library for model-level matedata validation

Table of Contents

Installation

    pip install oarepo-validate

Usage

The library provides mixins for enforcing json schema and marshmallow validation.

JSON schema validation

If $schema is present on metadata, invenio performs a json schema validation inside the validate() method. The problem is that $schema can be set/removed via the REST API. This means that an ill-written client can completely bypass the validation.

To mitigate this issue, create your own Record implementation:

from oarepo_validate import SchemaKeepingRecordMixin
from invenio_records import Record

class MyRecord(SchemaKeepingRecordMixin, Record):
    ALLOWED_SCHEMAS = ('records/record-v1.0.0.json', 'records/record-v2.0.0.json')
    PREFERRED_SCHEMA = 'records/record-v2.0.0.json'

And register the record in REST endpoints in configuration:

RECORD_PID = 'pid(recid,record_class="my:MyRecord")'

RECORDS_REST_ENDPOINTS = {
    'records': dict(
        pid_type='recid',
        pid_minter='recid',
        pid_fetcher='recid',
        record_class='my:MyRecord',
        item_route='/records/<{0}:pid_value>'.format(RECORD_PID),
        # ...
    )
}

Create record

When creating a new record, if $schema is not set, MyRecord.PREFERRED_SCHEMA is added automatically. If $schema is set, it is validated against MyRecord.ALLOWED_SCHEMAS and an exception is raised if the schema is not present in ALLOWED_SCHEMAS.

PUT / PATCH record

Before the result of the operation is committed, $schema is checked again.

Marshmallow validation

In invenio, REST create operation use the following sequence:

<flask>
<invenio_records_rest.views.RecordsListResource:post>
   <loader>
      <marshmallow>
   <permission factory>
   <pid minter>
   <record_class.create>
      <record.commit>
         <record.validate>

REST PUT operation then uses:

<flask>
<invenio_records_rest.views.RecordResource:put>
   <permission factory>
   <loader>
      <marshmallow>
   <record.update>
   <record.commit>
      <record.validate>

REST PATCH operation:

<flask>
<invenio_records_rest.views.RecordResource:put>
   <permission factory>
   <simple json loader>
   <record.patch>
   <record.commit>
      <record.validate>

As you can see, if you place any validation code in loader's marshmallow, it is not executed. An alternative is to have the validation code in validate and handle all validations there. This library does exactly this - it provides a record mixin that calls marshmallow schema's load method inside its validate method.

Usage

Create your own record and inherit from the mixin:

from oarepo_validate import MarshmallowValidatedRecordMixin
from invenio_records import Record
from marshmallow import Schema, fields

class TestSchema(Schema):
    name = fields.Str(required=True)

class MyRecord(MarshmallowValidatedRecordMixin, Record):
    MARSHMALLOW_SCHEMA = TestSchema

Do not forget to register it as in the previous example.

Now marshmallow schema will be processed before each commit method.

What about marshmallow in loader?

In most cases, marshmallow schema in loader can be removed and a simple json loader used instead. However, if you need a custom processing of input data that is independent of validation, you can keep the two marshmallows. To remove marshmallow loader and use a simple one, set oarepo_validate.json_loader as the record loader.

RECORDS_REST_ENDPOINTS = {
    'recid': dict(
        record_loaders={
            'application/json': 'oarepo_validate:json_loader',
        },
        # ...
    )
}

A special case is when the marshmallow in loader already includes validation marshmallow rules. Then you would want to use loader's marshmallow for create / replace and marshmallow in validation only for patch operation (so that the same marshmallow rules are not called twice). To accomplish this, set:

class MyRecord(MarshmallowValidatedRecordMixin, Record):
    MARSHMALLOW_SCHEMA = TestSchema

    VALIDATE_MARSHMALLOW = False
    VALIDATE_PATCH = True

VALIDATE_MARSHMALLOW will switch off marshmallow validation in validate method and VALIDATE_PATCH will switch on marshmallow validation in patch method.

record-files

Be careful with removing the loader when you use invenio-record-files. Just using plain json loader makes it possible to set _bucket and _files directly which should be disabled for security reasons (anyone might gain access to any file if he knows bucket and object version of the file and has write access to any record).

To fix this, set:

from oarepo_validate import FilesKeepingRecordMixin

RECORDS_REST_ENDPOINTS = {
    'recid': dict(
        record_loaders={
            'application/json': 'oarepo_validate:json_loader',
        },
        # ...
    )
}

class MyRecord(FilesKeepingRecordMixin, ...):
    ...

The loader will strip _bucket and _files from the payload and the mixin will make sure that the files can not be removed with put or replaced with patch operation.

Context

Marshmallow validation is called with a context, that is filled with:

  • record
  • pid if it is known
  • Any **kwargs passed to Record.create or Record.commit

Output of marshmallow validation

Valid data

The marshmallow loader produces validated data. Be default, the validated data are merged into the record. The rationale for this is that the validation might be used to replace content (include referenced content, etc). To have a consistent processing, the schema must be idempotent, that is schema(schema(input)) == schema(input).

To prevent this behaviour, set MERGE_WITH_VALIDATED to False on your record class.

Invalid data

Even in the case the data are invalid, marshmallow validation might still return a partially valid output (in ValidationError.valid_data). This library merges the valid data into the record's metadata. This behaviour can be switched off by setting MERGE_WITH_VALIDATED_ERROR = False on your record class.

Merging process

The merging process is recursive and is designed to preserve values in the record's metadata if they are not present in the validated metadata. This means:

  • lists are merged item-wise. If the list in the record is longer than in validated data, extra items are kept.
  • dictionaries are merged based on the same key. If a key is both in the record and in validated data, the respective values are merged recursively and the result used. Extra keys from validated data are copied into the record's metadata and keys present in record's metadata and ommited from validated data are kept.

Sometimes it might be necessary to prevent this merging. The library provides:

  • Keep(value) - if an instance of Keep class is returned, no merging is performed and the value is used as is - that is, it will overwrite anything in the record
  • DELETED - if this constant is returned, the item will be deleted - if it is a part of an array, the corresponding array item in record's metadata is deleted. If it is a value of a key in the dictionary, the corresponding key in record's metadata is deleted.

Signals

The library provides the following signals:

before_marshmallow_validate = signal('oarepo_before_marshmallow_validate')
"""
Signal invoked before record metadata are validated (loaded by marshmallow schema)
inside Record.validate

:param source:  the record being validated
:param record:  the record being validated
:param context: marshmallow context
:param **kwargs: kwargs passed to Record.create or Record.commit (or Record.validate)
"""

after_marshmallow_validate = signal('oarepo_after_marshmallow_validate')
"""
Signal invoked after record metadata are validated (loaded by marshmallow schema)
inside Record.validate

:param source:  the record being validated
:param record:  the record that was successfully validated
:param context: marshmallow context
:param result:  result of load that will be used to update record's metadata.
                Signal handler can modify it. In case of validation exception the result is None.
:param error:   Exception raised when validating. None if validation has been successful
:param **kwargs: kwargs passed to Record.create or Record.commit (or Record.validate)
"""

Serializers

If marhsmallow.dump is not required for metadata serialization, oarepo_validate.json_search, oarepo_validate.json_response are faster replacements for marshmallow-based serializers:

RECORDS_REST_ENDPOINTS = {
    'recid': dict(
        record_serializers={
            'application/json': 'oarepo_validate:json_response',
        },
        search_serializers={
            'application/json': 'oarepo_validate:json_search',
        }
    )
}

Changes

Version 1.2.3 (released 2020-08-30)

  • Handling pid field in search hit serialization

Version 1.2.2 (released 2020-08-25)

  • Handling pid field in record serialization

Version 1.2.1 (released 2020-08-25)

  • Keeping schema in Record.__init__ (useful mostly for tests)

Version 1.2.0 (released 2020-08-25)

  • Added marshmallow-less loaders and serializers

Version 1.1.0 (released 2020-08-18)

  • Added before and after validation signals.

Version 1.0.0 (released 2020-08-16)

  • Initial public release.

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