Those were the days :)

I believe that we made a few mistakes with Opa, though. The slicer (the component of the compiler that decided which code should be compiled to client and whic hto server) was a great idea, but it came with considerable pitfalls in terms of security. Since then, I have concluded that too much multi-tier magic is actually a bad thing.

If I were to start a new version of Opa, I would probably force developers to split their code manually between client, server, database and location-independent (presumably by putting stuff in distinct directories). This would be much easier to read/audit. But at this stage, this raises the question of whether an entirely new language is really useful. Why not simply do it with a sufficiently smart toolchain based on TypeScript or any language that compiles to wasm?

Source: I did not start the project but I led the design and implementation.