70 lines
2.8 KiB
Python
70 lines
2.8 KiB
Python
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from django.db.migrations import operations
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from django.db.migrations.migration import Migration
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class AutoDetector(object):
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"""
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Takes a pair of ProjectStates, and compares them to see what the
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first would need doing to make it match the second (the second
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usually being the project's current state).
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Note that this naturally operates on entire projects at a time,
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as it's likely that changes interact (for example, you can't
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add a ForeignKey without having a migration to add the table it
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depends on first). A user interface may offer single-app detection
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if it wishes, with the caveat that it may not always be possible.
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"""
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def __init__(self, from_state, to_state):
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self.from_state = from_state
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self.to_state = to_state
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def changes(self):
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"""
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Returns a set of migration plans which will achieve the
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change from from_state to to_state.
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"""
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# We'll store migrations as lists by app names for now
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self.migrations = {}
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# Stage one: Adding models.
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added_models = set(self.to_state.keys()) - set(self.from_state.keys())
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for app_label, model_name in added_models:
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model_state = self.to_state[app_label, model_name]
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self.add_to_migration(
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app_label,
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operations.CreateModel(
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model_state.name,
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model_state.fields,
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model_state.options,
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model_state.bases,
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)
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)
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# Removing models
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removed_models = set(self.from_state.keys()) - set(self.to_state.keys())
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for app_label, model_name in removed_models:
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model_state = self.from_state[app_label, model_name]
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self.add_to_migration(
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app_label,
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operations.DeleteModel(
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model_state.name,
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)
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)
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# Alright, now sort out and return the migrations
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for app_label, migrations in self.migrations.items():
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for m1, m2 in zip(migrations, migrations[1:]):
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m2.dependencies.append((app_label, m1.name))
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# Flatten and return
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result = set()
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for app_label, migrations in self.migrations.items():
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for migration in migrations:
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subclass = type("Migration", (Migration,), migration)
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instance = subclass(migration['name'], app_label)
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result.append(instance)
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return result
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def add_to_migration(self, app_label, operation):
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migrations = self.migrations.setdefault(app_label, [])
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if not migrations:
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migrations.append({"name": "temp-%i" % len(migrations) + 1, "operations": [], "dependencies": []})
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migrations[-1].operations.append(operation)
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