[App] Introduce Commands

[tchaton]

What does this PR do?

This PR introduces Lightning App Commands.

Commands can be configured from the app by overriding the configure_commands hook on the flow and returning a list of dictionaries mapping a command_name to a flow method.

Once the app is running, someone can remotely execute those methods from the CLI by providing the command_name.

Here is how it looks:

from lightning import LightningFlow
from lightning_app.core.app import LightningApp


class ChildFlow(LightningFlow):
    def trigger_method(self, name: str):
        print(name)

    def configure_commands(self):
        return [{"nested_trigger_command": self.trigger_method}]


class FlowCommands(LightningFlow):
    def __init__(self):
        super().__init__()
        self.names = []
        self.child_flow = ChildFlow()

    def run(self):
        if len(self.names):
            print(self.names)

    def trigger_method(self, name: str):
        self.names.append(name)

    def configure_commands(self):
        return [{"flow_trigger_command": self.trigger_method}] + self.child_flow.configure_commands()


app = LightningApp(FlowCommands())

Once the app is running with

lightning run app app.py

Trigger one of its commands as follows

lightning run command flow_trigger_command --args name=my_name

To make it work in the cloud, add id.

lightning run command flow_trigger_command --args name=my_name --id=01g7q3kg9kvtsdx4ak0cdmrbe8

Fixed #13637

Alternatives API:

• lightning run function
• lightning run task
• lightning exec ...
• lightning execute

Does your PR introduce any breaking changes? If yes, please list them.

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Did you have fun?

Make sure you had fun coding 🙃

cc @Borda

[manskx]

🚀

dismiss

[awaelchli]

unblock

[Borda]

Just curious, are this env. var described somewhere?

[Borda]

Can this accidentally turn into an infinite loop?

[Borda]

@tchaton / @manskx Can we add as a follow-up also exception types?

[Borda]

we do not use r in these simple strings :)

[Borda]

@tchaton, mind adding some more docstrings to newly added classes? 🐰