import re from django.utils.six.moves import input from django.db.migrations import operations from django.db.migrations.migration import Migration from django.db.models.loading import cache class MigrationAutodetector(object): """ Takes a pair of ProjectStates, and compares them to see what the first would need doing to make it match the second (the second usually being the project's current state). Note that this naturally operates on entire projects at a time, as it's likely that changes interact (for example, you can't add a ForeignKey without having a migration to add the table it depends on first). A user interface may offer single-app usage if it wishes, with the caveat that it may not always be possible. """ def __init__(self, from_state, to_state, questioner=None): self.from_state = from_state self.to_state = to_state self.questioner = questioner or MigrationQuestioner() def changes(self): """ Returns a dict of migration plans which will achieve the change from from_state to to_state. The dict has app labels as kays and a list of migrations as values. The resulting migrations aren't specially named, but the names do matter for dependencies inside the set. """ # We'll store migrations as lists by app names for now self.migrations = {} # Adding models. added_models = set(self.to_state.models.keys()) - set(self.from_state.models.keys()) for app_label, model_name in added_models: model_state = self.to_state.models[app_label, model_name] self.add_to_migration( app_label, operations.CreateModel( name = model_state.name, fields = model_state.fields, options = model_state.options, bases = model_state.bases, ) ) # Removing models removed_models = set(self.from_state.models.keys()) - set(self.to_state.models.keys()) for app_label, model_name in removed_models: model_state = self.from_state.models[app_label, model_name] self.add_to_migration( app_label, operations.DeleteModel( model_state.name, ) ) # Changes within models kept_models = set(self.from_state.models.keys()).intersection(self.to_state.models.keys()) for app_label, model_name in kept_models: old_model_state = self.from_state.models[app_label, model_name] new_model_state = self.to_state.models[app_label, model_name] # New fields old_field_names = set([x for x, y in old_model_state.fields]) new_field_names = set([x for x, y in new_model_state.fields]) for field_name in new_field_names - old_field_names: self.add_to_migration( app_label, operations.AddField( model_name = model_name, name = field_name, field = [y for x, y in new_model_state.fields if x == field_name][0], ) ) # Old fields for field_name in old_field_names - new_field_names: self.add_to_migration( app_label, operations.RemoveField( model_name = model_name, name = field_name, ) ) # Alright, now add internal dependencies for app_label, migrations in self.migrations.items(): for m1, m2 in zip(migrations, migrations[1:]): m2.dependencies.append((app_label, m1.name)) return self.migrations def add_to_migration(self, app_label, operation): migrations = self.migrations.setdefault(app_label, []) if not migrations: subclass = type("Migration", (Migration,), {"operations": [], "dependencies": []}) instance = subclass("auto_%i" % (len(migrations) + 1), app_label) migrations.append(instance) migrations[-1].operations.append(operation) def arrange_for_graph(self, changes, graph): """ Takes in a result from changes() and a MigrationGraph, and fixes the names and dependencies of the changes so they extend the graph from the leaf nodes for each app. """ leaves = graph.leaf_nodes() name_map = {} for app_label, migrations in list(changes.items()): if not migrations: continue # Find the app label's current leaf node app_leaf = None for leaf in leaves: if leaf[0] == app_label: app_leaf = leaf break # Do they want an initial migration for this app? if app_leaf is None and not self.questioner.ask_initial(app_label): # They don't. for migration in migrations: name_map[(app_label, migration.name)] = (app_label, "__first__") del changes[app_label] # Work out the next number in the sequence if app_leaf is None: next_number = 1 else: next_number = (self.parse_number(app_leaf[1]) or 0) + 1 # Name each migration for i, migration in enumerate(migrations): if i == 0 and app_leaf: migration.dependencies.append(app_leaf) if i == 0 and not app_leaf: new_name = "0001_initial" else: new_name = "%04i_%s" % (next_number, self.suggest_name(migration.operations)) name_map[(app_label, migration.name)] = (app_label, new_name) migration.name = new_name # Now fix dependencies for app_label, migrations in changes.items(): for migration in migrations: migration.dependencies = [name_map.get(d, d) for d in migration.dependencies] return changes def trim_to_apps(self, changes, app_labels): """ Takes changes from arrange_for_graph and set of app labels and returns a modified set of changes which trims out as many migrations that are not in app_labels as possible. Note that some other migrations may still be present, as they may be required dependencies. """ # Gather other app dependencies in a first pass app_dependencies = {} for app_label, migrations in changes.items(): for migration in migrations: for dep_app_label, name in migration.dependencies: app_dependencies.setdefault(app_label, set()).add(dep_app_label) required_apps = set(app_labels) # Keep resolving till there's no change old_required_apps = None while old_required_apps != required_apps: old_required_apps = set(required_apps) for app_label in list(required_apps): required_apps.update(app_dependencies.get(app_label, set())) # Remove all migrations that aren't needed for app_label in list(changes.keys()): if app_label not in required_apps: del changes[app_label] return changes @classmethod def suggest_name(cls, ops): """ Given a set of operations, suggests a name for the migration they might represent. Names not guaranteed to be unique; they must be prefixed by a number or date. """ if len(ops) == 1: if isinstance(ops[0], operations.CreateModel): return ops[0].name.lower() elif isinstance(ops[0], operations.DeleteModel): return "delete_%s" % ops[0].name.lower() elif all(isinstance(o, operations.CreateModel) for o in ops): return "_".join(sorted(o.name.lower() for o in ops)) return "auto" @classmethod def parse_number(cls, name): """ Given a migration name, tries to extract a number from the beginning of it. If no number found, returns None. """ if re.match(r"^\d+_", name): return int(name.split("_")[0]) return None class MigrationQuestioner(object): """ Gives the autodetector responses to questions it might have. This base class has a built-in noninteractive mode, but the interactive subclass is what the command-line arguments will use. """ def __init__(self, defaults=None): self.defaults = defaults or {} def ask_initial(self, app_label): "Should we create an initial migration for the app?" return self.defaults.get("ask_initial", False) class InteractiveMigrationQuestioner(MigrationQuestioner): def __init__(self, specified_apps=set()): self.specified_apps = specified_apps def _boolean_input(self, question): result = input("%s " % question) while len(result) < 1 or result[0].lower() not in "yn": result = input("Please answer yes or no: ") return result[0].lower() == "y" def ask_initial(self, app_label): # Don't ask for django.contrib apps app = cache.get_app(app_label) if app.__name__.startswith("django.contrib"): return False # If it was specified on the command line, definitely true if app_label in self.specified_apps: return True # Now ask return self._boolean_input("Do you want to enable migrations for app '%s'?" % app_label)