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79 lines
2.5 KiB
Python
79 lines
2.5 KiB
Python
from django.db.models.query_utils import DeferredAttribute
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from netbox.registry import registry
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class Tracker:
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"""
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An ephemeral instance employed to record which tracked fields on an instance have been modified.
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"""
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def __init__(self):
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self._changed_fields = {}
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def __contains__(self, item):
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return item in self._changed_fields
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def set(self, name, value):
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"""
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Mark an attribute as having been changed and record its original value.
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"""
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self._changed_fields[name] = value
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def get(self, name):
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"""
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Return the original value of a changed field. Raises KeyError if name is not found.
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"""
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return self._changed_fields[name]
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def clear(self, *names):
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"""
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Clear any fields that were recorded as having been changed.
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"""
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for name in names:
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self._changed_fields.pop(name, None)
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else:
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self._changed_fields = {}
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class TrackingModelMixin:
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def __init__(self, *args, **kwargs):
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super().__init__(*args, **kwargs)
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# Mark the instance as initialized, to enable our custom __setattr__()
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self._initialized = True
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@property
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def tracker(self):
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"""
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Return the Tracker instance for this instance, first creating it if necessary.
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"""
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if not hasattr(self._state, "_tracker"):
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self._state._tracker = Tracker()
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return self._state._tracker
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def save(self, *args, **kwargs):
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super().save(*args, **kwargs)
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# Clear any tracked fields now that changes have been saved
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update_fields = kwargs.get('update_fields', [])
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self.tracker.clear(*update_fields)
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def __setattr__(self, name, value):
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if hasattr(self, "_initialized"):
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# Record any changes to a tracked field
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if name in registry['counter_fields'][self.__class__]:
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if name not in self.tracker:
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# The attribute has been created or changed
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if name in self.__dict__:
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old_value = getattr(self, name)
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if value != old_value:
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self.tracker.set(name, old_value)
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else:
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self.tracker.set(name, DeferredAttribute)
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elif value == self.tracker.get(name):
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# A previously changed attribute has been restored
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self.tracker.clear(name)
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super().__setattr__(name, value)
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