We'll be looking at Python in the coming weeks, currently it's JS and TS only.
But the way this works locally (for Node) is that you do an npm install just as you would and it executes your application locally. The packaging part comes into play when deploying these functions to AWS. And I agree that portion even for Node isn't bullet proof. It's something we want to do a better job of.
Wait so you automatically deploy the lambda dependencies for me. The other issue I run into is occasionally you have to split npm packages into different layers when you deploy lambdas. I don't have time personally to contribute, but I hope you're able to develop this into something which becomes a part of my workflow.
So the `sst start` command fires up a local environment but it doesn't deploy your functions. Instead it'll run it locally when it gets invoked.
But when you `sst deploy` it, we'll package your functions. To do this we use esbuild (https://esbuild.github.io), it's like Webpack but 10x faster. It'll generated a single js file that should be fairly small and you shouldn't have to use Layers.
However, this isn't bullet proof. There are some dependencies that are not compatible with esbuild/webpack, and you'll end up having to zip them up as a directory. That's something we are going to work to improve in the future.
But the way this works locally (for Node) is that you do an npm install just as you would and it executes your application locally. The packaging part comes into play when deploying these functions to AWS. And I agree that portion even for Node isn't bullet proof. It's something we want to do a better job of.