Streamlines a common middleware pattern and provides foundations for avoiding variably sized v8::ExternalReferences & enabling fully monomorphic op callpaths
This speeds up incremental rebuild when only touching JS files by 13-15%
Rebuild time after `touch 01_broadcast_channel.js`:
main: run 1 49.18s, run 2 50.34s
this: run 1 43.12s, run 2 43.19s
Extensions allow declarative extensions to "JsRuntime" (ops, state, JS or middleware).
This allows for:
- `op_crates` to be plug-and-play & self-contained, reducing complexity leaked to consumers
- op middleware (like metrics_op) to be opt-in and for new middleware (unstable, tracing,...)
- `MainWorker` and `WebWorker` to be composable, allowing users to extend workers with their ops whilst benefiting from the other infrastructure (inspector, etc...)
In short extensions improve deno's modularity, reducing complexity and leaky abstractions for embedders and the internal codebase.
