Have you considered allowing Tortoise to be independently initialized multiple times in different packages?

[zhaowanpeng]

Imagine a scenario where we are using an open-source package based on Tortoise, and our own project also uses Tortoise. However, because Tortoise can only be initialized once, the package developed with Tortoise is not convenient for others to directly import and use.

[zhaowanpeng]

One great feature of Django is that everyone can develop applications, and others can easily import these applications.

Using someone else's app only requires simple import and initialization, without the need to delve deeply into their code.

Currently, Tortoise is also widely used in frameworks like FastAPI. However, Tortoise's unified initialization mechanism makes it difficult to achieve convenient app modularity.

This hinders the ease of combining open-source code based on Tortoise, making it hard for others to integrate such code flexibly into their projects.

[abondar]

Hello!

Yes, I considered it while ago, even had most of work done then, but didn't finish it, as it got tied up with migration work that I started, but never finished, sadly
#406

May be some day I will find time to rework it again, based on actual master, but right now I don't have much time

[zhaowanpeng]

Thank you for your response.

I have tried to initialize separately, but I lack an overall understanding of Tortoise's logic, and I believe that what I wrote is not professional and standardized enough.I am concerned that my approach may cause potential issues with other methods.

Here is my code. If it is feasible, I hope you can give me some suggestions for modification, and I will make the changes, or you can modify it. I hope it can be included in future upgrades.

`
usage:

    In admin.py

    await TameTortoise.load_app(
        db_url="mysql://user:[email protected]:3306/dbname",
        app_name="admin",
        models_paths=["admin.models.rbac",
                        "admin.models.system"],
    )
    await Tortoise.generate_schemas()


    In other.py
    await TameTortoise.load_app(
        db_url="mysql://user:[email protected]:3306/dbname",
        app_name="other",
        models_paths=["other.models.base",],
    )
    await Tortoise.generate_schemas()

`

`
class TameTortoise(Tortoise):

dburl_name: Dict = {}
apps_modules: Dict = {}

@classmethod
def _init_relations_alone(cls, alone_app_name: str) -> None:

    def get_related_model(related_app_name_: str, related_model_name_: str) -> Type["Model"]:
        try:
            return cls.apps[related_app_name_][related_model_name_]
        except KeyError:
            if related_app_name_ not in cls.apps:
                raise ConfigurationError(
                    f"No app with name '{related_app_name_}' registered."
                    f" Please check your model names in ForeignKeyFields"
                    f" and configurations."
                )
            raise ConfigurationError(
                f"No model with name '{related_model_name_}' registered in"
                f" app '{related_app_name_}'."
            )

    def split_reference(reference_: str) -> Tuple[str, str]:
        """
        Test, if reference follow the official naming conventions. Throws a
        ConfigurationError with a hopefully helpful message. If successful,
        returns the app and the model name.

        :raises ConfigurationError: If no model reference is invalid.
        """
        items = reference_.split(".")
        if len(items) != 2:  # pragma: nocoverage
            raise ConfigurationError(
                (
                    "'%s' is not a valid model reference Bad Reference."
                    " Should be something like <appname>.<modelname>."
                )
                % reference
            )

        return (items[0], items[1])

    # for app_name, app in {alone_app_name: cls.apps[alone_app_name]}:
    app_name = alone_app_name

    for model_name, model in cls.apps[alone_app_name].items():
        if model._meta._inited:
            continue
        model._meta._inited = True
        if not model._meta.db_table:
            model._meta.db_table = model.__name__.lower()

        for field in sorted(model._meta.fk_fields):
            fk_object = cast(ForeignKeyFieldInstance, model._meta.fields_map[field])
            reference = fk_object.model_name
            related_app_name, related_model_name = split_reference(reference)
            related_model = get_related_model(related_app_name, related_model_name)

            if fk_object.to_field:
                related_field = related_model._meta.fields_map.get(fk_object.to_field, None)
                if related_field:
                    if related_field.unique:
                        key_fk_object = deepcopy(related_field)
                        fk_object.to_field_instance = related_field  # type: ignore
                    else:
                        raise ConfigurationError(
                            f'field "{fk_object.to_field}" in model'
                            f' "{related_model_name}" is not unique'
                        )
                else:
                    raise ConfigurationError(
                        f'there is no field named "{fk_object.to_field}"'
                        f' in model "{related_model_name}"'
                    )
            else:
                key_fk_object = deepcopy(related_model._meta.pk)
                fk_object.to_field_instance = related_model._meta.pk  # type: ignore
                fk_object.to_field = related_model._meta.pk_attr
            fk_object.field_type = fk_object.to_field_instance.field_type
            key_field = f"{field}_id"
            key_fk_object.pk = False
            key_fk_object.unique = False
            key_fk_object.index = fk_object.index
            key_fk_object.default = fk_object.default
            key_fk_object.null = fk_object.null
            key_fk_object.generated = fk_object.generated
            key_fk_object.reference = fk_object
            key_fk_object.description = fk_object.description
            if fk_object.source_field:
                key_fk_object.source_field = fk_object.source_field
            else:
                key_fk_object.source_field = key_field
            model._meta.add_field(key_field, key_fk_object)

            fk_object.related_model = related_model
            fk_object.source_field = key_field
            backward_relation_name = fk_object.related_name
            if backward_relation_name is not False:
                if not backward_relation_name:
                    backward_relation_name = f"{model._meta.db_table}s"
                if backward_relation_name in related_model._meta.fields:
                    raise ConfigurationError(
                        f'backward relation "{backward_relation_name}" duplicates in'
                        f" model {related_model_name}"
                    )
                fk_relation = BackwardFKRelation(
                    model,
                    f"{field}_id",
                    key_fk_object.source_field,
                    fk_object.null,
                    fk_object.description,
                )
                fk_relation.to_field_instance = fk_object.to_field_instance  # type: ignore
                related_model._meta.add_field(backward_relation_name, fk_relation)

        for field in model._meta.o2o_fields:
            o2o_object = cast(OneToOneFieldInstance, model._meta.fields_map[field])
            reference = o2o_object.model_name
            related_app_name, related_model_name = split_reference(reference)
            related_model = get_related_model(related_app_name, related_model_name)

            if o2o_object.to_field:
                related_field = related_model._meta.fields_map.get(
                    o2o_object.to_field, None
                )
                if related_field:
                    if related_field.unique:
                        key_o2o_object = deepcopy(related_field)
                        o2o_object.to_field_instance = related_field  # type: ignore
                    else:
                        raise ConfigurationError(
                            f'field "{o2o_object.to_field}" in model'
                            f' "{related_model_name}" is not unique'
                        )
                else:
                    raise ConfigurationError(
                        f'there is no field named "{o2o_object.to_field}"'
                        f' in model "{related_model_name}"'
                    )
            else:
                key_o2o_object = deepcopy(related_model._meta.pk)
                o2o_object.to_field_instance = related_model._meta.pk  # type: ignore
                o2o_object.to_field = related_model._meta.pk_attr

            o2o_object.field_type = o2o_object.to_field_instance.field_type

            key_field = f"{field}_id"
            key_o2o_object.pk = o2o_object.pk
            key_o2o_object.index = o2o_object.index
            key_o2o_object.default = o2o_object.default
            key_o2o_object.null = o2o_object.null
            key_o2o_object.unique = o2o_object.unique
            key_o2o_object.generated = o2o_object.generated
            key_o2o_object.reference = o2o_object
            key_o2o_object.description = o2o_object.description
            if o2o_object.source_field:
                key_o2o_object.source_field = o2o_object.source_field
            else:
                key_o2o_object.source_field = key_field
            model._meta.add_field(key_field, key_o2o_object)

            o2o_object.related_model = related_model
            o2o_object.source_field = key_field
            backward_relation_name = o2o_object.related_name
            if backward_relation_name is not False:
                if not backward_relation_name:
                    backward_relation_name = f"{model._meta.db_table}"
                if backward_relation_name in related_model._meta.fields:
                    raise ConfigurationError(
                        f'backward relation "{backward_relation_name}" duplicates in'
                        f" model {related_model_name}"
                    )
                o2o_relation = BackwardOneToOneRelation(
                    model,
                    f"{field}_id",
                    key_o2o_object.source_field,
                    null=True,
                    description=o2o_object.description,
                )
                o2o_relation.to_field_instance = o2o_object.to_field_instance  # type: ignore
                related_model._meta.add_field(backward_relation_name, o2o_relation)

            if o2o_object.pk:
                model._meta.pk_attr = key_field

        for field in list(model._meta.m2m_fields):
            m2m_object = cast(ManyToManyFieldInstance, model._meta.fields_map[field])
            if m2m_object._generated:
                continue

            backward_key = m2m_object.backward_key
            if not backward_key:
                backward_key = f"{model._meta.db_table}_id"
                if backward_key == m2m_object.forward_key:
                    backward_key = f"{model._meta.db_table}_rel_id"
                m2m_object.backward_key = backward_key

            reference = m2m_object.model_name
            related_app_name, related_model_name = split_reference(reference)
            related_model = get_related_model(related_app_name, related_model_name)

            m2m_object.related_model = related_model

            backward_relation_name = m2m_object.related_name
            if not backward_relation_name:
                backward_relation_name = (
                    m2m_object.related_name
                ) = f"{model._meta.db_table}s"
            if backward_relation_name in related_model._meta.fields:
                raise ConfigurationError(
                    f'backward relation "{backward_relation_name}" duplicates in'
                    f" model {related_model_name}"
                )

            if not m2m_object.through:
                related_model_table_name = (
                    related_model._meta.db_table
                    if related_model._meta.db_table
                    else related_model.__name__.lower()
                )

                m2m_object.through = f"{model._meta.db_table}_{related_model_table_name}"

            m2m_relation = ManyToManyFieldInstance(
                f"{app_name}.{model_name}",
                m2m_object.through,
                forward_key=m2m_object.backward_key,
                backward_key=m2m_object.forward_key,
                related_name=field,
                field_type=model,
                description=m2m_object.description,
            )
            m2m_relation._generated = True
            model._meta.filters.update(get_m2m_filters(field, m2m_object))
            related_model._meta.add_field(backward_relation_name, m2m_relation)

@classmethod
async def load_app(cls,
                   app_name: str,
                   models_paths: Iterable[Union[ModuleType, str]],
                   db_url: str,
                   use_tz: bool = False,
                   timezone: str = "Asia/Shanghai",
                   generate: bool = False,
                   create_db: bool = False,
                   ) -> None:
    # 如果是字符串,处理为列表
    models_paths = [models_paths] if isinstance(models_paths, str) else models_paths

    if app_name in cls.apps_modules:
        raise ValueError(f"{app_name} has already been initialized.")
    cls.apps_modules[app_name] = models_paths

    # db_url's name default use 'default'
    cls.dburl_name[db_url] = "default"
    # if db_url is new, use app_name as its name
    if db_url not in cls.dburl_name:
        cls.dburl_name[db_url] = app_name

    # create config
    db_name = cls.dburl_name[db_url]
    config = generate_config(db_url, {app_name: models_paths}, db_name)

    # init timezone
    cls._init_timezone(use_tz, timezone)

    # init db
    connections_config = config["connections"]
    await connections._init(connections_config, create_db)

    # init app models
    apps_config = config["apps"]
    cls._init_apps_alone(apps_config, app_name)

    cls._init_routers(None)
    cls._inited = True

@classmethod
def _init_apps_alone(cls, apps_config: dict, app_name: str) -> None:
    for name, info in apps_config.items():
        try:
            connections.get(info.get("default_connection", "default"))
        except KeyError:
            raise ConfigurationError(
                'Unknown connection "{}" for app "{}"'.format(
                    info.get("default_connection", "default"), name
                )
            )

        cls.init_models(info["models"], name, _init_relations=False)

        for model in cls.apps[name].values():
            model._meta.default_connection = info.get("default_connection", "default")

    cls._init_relations_alone(app_name)

    cls._build_initial_querysets_alone(app_name)

@classmethod
def _build_initial_querysets_alone(cls, app_name: str) -> None:

    for model in cls.apps[app_name].values():
        model._meta.finalise_model()
        model._meta.basetable = Table(name=model._meta.db_table, schema=model._meta.schema)
        model._meta.basequery = model._meta.db.query_class.from_(model._meta.basetable)
        model._meta.basequery_all_fields = model._meta.basequery.select(
            *model._meta.db_fields
        )

`