60 lines
2 KiB
Python
60 lines
2 KiB
Python
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import jsonschema
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class StructuredDict(dict):
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"""
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A dictionary that enforces a structure specified by a schema, and supports
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migration between different versions of the schema.
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"""
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# To be specified in sub-classes, an array in the format
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# [(version, schema, migration), ...]
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_versions = []
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# Used internally to allow schema lookups by version number
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_schemas = {}
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version = None
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def __init__(self, value, starting_version, migrate=True, target_version=None):
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dict.__init__(self, value)
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self.version = starting_version
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self._schemas = dict([(version, schema) for (version, schema, _) in self._versions])
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self.validate(starting_version)
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if migrate:
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self.migrate(target_version)
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def _upgrade_version_range(self, start_version, end_version):
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after_starting_version = False
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for version, schema, migration in self._versions:
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if not after_starting_version:
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if version == self.version:
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after_starting_version = True
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continue
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yield version, schema, migration
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if end_version and version == end_version:
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break
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def validate(self, version):
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jsonschema.validate(self, self._schemas[version])
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def migrate(self, target_version=None):
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if target_version:
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assert self._versions.index(target_version) > self._versions.index(self.version), \
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"Current version is above target version"
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for version, schema, migration in self._upgrade_version_range(self.version, target_version):
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migration(self)
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try:
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self.validate(version)
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except jsonschema.ValidationError as e:
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raise jsonschema.ValidationError(
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"Could not migrate to version %s due to validation error: %s" %
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(version, e.message))
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self.version = version
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