[Feature] Support Runtime Dependency Injection in Configs via ObjectHub

[IonThief]

What is the feature?

Motivation

Currently, linking components (for example, passing backbone.out_channels to neck) requires either:

• Hardcoding values in the config (error-prone)

• Writing "glue code" inside parent classes (i.e. Detector), which tightly couples components and requires modifying source code to change data flow.

Limiting the ability to compose generic components dynamically.

Proposal

Introduce ObjectHub to enable runtime parameter resolution directly within build_from_cfg.

Design

ObjectHub: A global registry (inheriting ManagerMixin) that manages live instances, scoped to the current experiment.

_alias_: A new config reserved key that registers the built instance to the hub.

@ syntax: String arguments starting with @ are resolved dynamically against registered objects.

Example

model = dict(
    type='Detector',
    backbone=dict(
        type='ResNet',
        depth=50,
        _alias_='first_backbone'  # Register instance
    ),
    neck=dict(
        type='FPN',
        in_channels='@first_backbone.out_channels' # Resolve attribute at runtime
    )
)

Status

I have a prototype ready.

It supports:

• recursive resolution (@backbone.meta.version)
• private attribute protection,
• and is isolated by Runner experiment name.

Any other context?

No response