dagger

I learned a ton about Java and pragmatic algorithm development from reading Dagger (https://github.com/square/dagger) and porting it to C#. It's small enough that you can grok it in a reasonable amount of time, but sophisticated enough that there's a lot to learn. (Yes it's deprecated in favor of Dagger 2, but the latter is a tougher slog IMO) Actually most of the big Square OSS libraries are great to read - okio, okhttp, picasso.

The specific systems I'm thinking of were Google-internal, but there's a close public analogue with Guice & Dagger: https://github.com/google/guice https://github.com/square/dagger Imagine injecting Futures into your code. Now imagine injecting them, but having the Provider record a lot of metadata about who you were calling, how you were calling it, how long it took, whether an error occurred, letting an SRE turn off the call, etc.

Yes, it builds upon it. It's a fork with some pretty large incompatible changes, based upon this proposal: https://github.com/square/dagger/issues/366 The documentation seems to still be in-flux, but there's some information about migration here: https://google.github.io/dagger/dagger-1-migration.html