We have a really big single page app, but there are entire subtrees of the mobx-state-tree that are unused by 99% of our users, so those would be good to lazy load

Setting up views and actions on a model is a method call itself, so you could theoretically defer the call to .views and .actions elsewhere.

trying to think of where that elsewhere could be... my kneejerk is like "could lazy loaded .views and .actions be chained onto an instance of a model"? not sure if that would be doable...can keep brainstorming but ideas/codesandbox welcome

also just for fun, our app is open source. mobx-state-tree from the start :)https://jbrowse.org

"could lazy loaded .views and .actions be chained onto an instance of a model"? not sure if that would be doable...can keep brainstorming but ideas/codesandbox welcome

Yup, this is precisely what I mean. You can chain any number of.props,.views,.actions, or.volatile calls onto a model at runtime. This still won't improve yourbundle size, but you could do this dynamically on certain routes so that the SPA itself doesn't pay the cost of instantiating models until you're certain one might be needed. So your runtime performance could be improved.

types.lazy will run all of the model instantiation lazily, but I don't think that's going to reduce your bundle size. The model definition will still exist.

This would improve your runtime performance so models don't go through their instantiation phase until after some asynchronous code has completed.