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databricks.labs.dqx.actions.registry

Registry of DQX action types, enabling custom (user-defined) actions.

An Action subclass becomes usable by DQAction — both programmatically and from YAML/JSON metadata — once it is registered here, keyed on its literal type discriminator. This follows the same registry idea as CHECK_FUNC_REGISTRY / register_rule for check functions, but with stricter collision handling: whereas register_rule is unconditionally last-write-wins, this registry raises InvalidActionError when a genuinely different class (different module / qualname) tries to claim a type that is already taken, so an accidental clash between two distinct actions surfaces loudly instead of one silently shadowing the other. Re-registering the same class — including the same definition re-run in a notebook cell or reloaded module, which yields a new class object with identical identity — is allowed and simply overwrites the previous registration, so interactive iteration on a custom action works without restarting the Python session.

Built-in actions register themselves at import time. A custom action registers via the register_action decorator (or register_action_class); the module defining it must be imported before the action is constructed or a metadata definition referencing its type is deserialized, so that registration has run.

register_action_class​

def register_action_class(action_cls: type[Action]) -> type[Action]

Register action_cls under its declared type discriminator.

Arguments:

  • action_cls - An Action subclass declaring a non-empty literal type field.

Returns:

The same action_cls, so this can be used as a decorator.

Raises:

  • InvalidActionError - If action_cls has no resolvable type, or if a genuinely different class (different module / qualname) is already registered under the same type. Re-registering the same class — or the same class redefined by a notebook cell re-run or a module reload, which produces a new class object with identical identity — is allowed and overwrites the previous registration.

register_action​

def register_action(action_cls: type[Action]) -> type[Action]

Decorator form of register_action_class.

Example:

>>> @register_action ... class MyAction(Action): ... type: Literal["my_action"] = "my_action" ... def execute(self, context, services): ...

resolve_action_type​

def resolve_action_type(action_type: str) -> type[Action]

Return the registered Action subclass for action_type.

Arguments:

  • action_type - The literal type discriminator to look up.

Returns:

The registered Action subclass.

Raises:

  • InvalidActionError - If no action is registered under action_type.