regex

That's a single benchmark. Before regex-redux was regex-dna, and Rust's regex engine was faster than PCRE2 on that benchmark. So how does that change your conclusion? The regex crate has many more benchmarks: https://github.com/rust-lang/regex/blob/master/bench/log/07/... and https://github.com/rust-lang/regex/blob/master/bench/log/07/... for example. And then there are things like this which can impact the performance of real world use cases: https://github.com/BurntSushi/ripgrep/blob/master/FAQ.md#pcr... Please don't draw sweeping conclusions about the comparative performance of regex engines from a single benchmark.

Some Rust libraries use a trick to make sum types extensible without introducing breaking changes when a new invariant is added. There is a private/undocumented invariant in the type so every pattern match over the type must have a default/catch-all/wildcard branch (e.g. it is not possible to do an exhaustive match by naming all existing variants). By having a default branch, the match is always exhaustive and there will be no error if a new variant is added. For fields in a sum type something similar can be done: an undocumented, hidden field that cannot be used when the variant is destructed. Therefore it can be only partially destructed and in this case it doesn't matter how many other fields there are in the type variant. Here is an example: https://github.com/rust-lang/regex/blob/master/regex-syntax/...

On the implementation's side, Russ Cox's articles are pretty indispensable: https://swtch.com/~rsc/regexp/regexp1.html https://swtch.com/~rsc/regexp/regexp2.html And actual implementations based on these articles: https://github.com/google/re2 and https://github.com/rust-lang/regex

I've never tried to compile to WASM. It really depends on how much of the OS APIs need to be fixed. e.g., I don't think WASM supports memory maps as one example. In that case, ripgrep could be made to compile without support for memory maps with a bit of work. But that's an easy case. What other things does WASM not support? What about typical file/directory APIs? I don't think it does, or it least, it looks like Rust's standard library doesn't implement anything for them: https://github.com/rust-lang/rust/blob/master/src/libstd/sys... At that point, it would be hopelessly difficult to build ripgrep. The right path then would be to build a new application that uses whatever of ripgrep's libraries make sense. Popping up a level though, why would you want to compile to WASM? If you're using Node, then surely you can build an FFI bridge to R