Add Official Lifecycle Hooks / Signals for Component Render & Method Calls

[JohananOppongAmoateng]

I’ve been experimenting with building a Debug Toolbar panel for Unicorn (on top of Django Debug Toolbar) to visualize:

• Components rendered during a request
• Component method calls
• Component state / frontend context
• Template names

Currently, the only way to achieve this is by monkey-patching:

• UnicornView.render
• UnicornView.call

While this works, it’s fragile and tightly coupled to internal implementation details.

Proposal

Introduce official lifecycle hooks (or Django signals) for key component events.

For example:

Component Rendered

Triggered after a component is rendered.

from django.dispatch import Signal

unicorn_component_rendered = Signal()

Sent with:

unicorn_component_rendered.send(
    sender=component.__class__,
    component=component,
    component_name=component.component_name,
    component_id=component.component_id,
    template_name=template_name,
    frontend_context=component.get_frontend_context_variables(),
)

Component Method Called

Triggered after a component method is invoked.

unicorn_component_method_called = Signal()

Sent with:

unicorn_component_method_called.send(
    sender=component.__class__,
    component=component,
    method_name=method_name,
    args=args,
    kwargs=kwargs,
    result=result,
    success=True,
)

And in exception cases:

success=False,
error=exception

[adamghill]

This makes sense to me, I never thought about using Signal before for this. Good idea!