Add subcommands to LightningCLI

[vikigenius]

I am not sure if this is possible and I am missing how to do this. But I couldn't figure out how to do it from the docs.

How can I add my own subcommands by extending LightningCLI ?

Say, my model code is part of an overall application I want to add a subcommand like preprocess for pre preparing data. Or serve for starting a dev webserver to serve the model etc ?

Is this possible with the current API? Are there any plans for it?

[mauvilsa]

It is possible. First you would subclass Trainer and add methods for each of the subcommands you want. These new methods should be usable independent of the CLI. Then you would need to subclass LightningCLI, in the __init__ make your new trainer the default and override https://github.com/Lightning-AI/lightning/blob/d4c7f91fec6f4cd8edf5124a5cdfac08a07c4bde/src/pytorch_lightning/utilities/cli.py#L534-L543