Improve performance of stdlib immutable Map on JavaScript

[schurhammer]

Issue gleam-lang/gleam#1262

Still WIP but creating PR for feedback.

Reference Implementation
https://github.com/clojure/clojure/blob/master/src/jvm/clojure/lang/PersistentHashMap.java

[schurhammer]

One question is where is isEqual and inspect implemented? I couldn't find the source files.
I think there might need to be some changes to these since the same set of entries could potentially have a different internal node structure, especially if/after items had been deleted from the map.

[inoas]

inspect is implemented in the ffi parts:

Erlang: https://github.com/gleam-lang/stdlib/blob/main/src/gleam_stdlib.erl#L324-L377=
JavaScript: https://github.com/gleam-lang/stdlib/blob/main/src/gleam_stdlib.mjs#L333= ... the JS part AFAIU leads into https://github.com/gleam-lang/gleam/blob/main/compiler-core/templates/prelude.js#L65-L67=

For isEqual see https://github.com/gleam-lang/gleam/blob/main/compiler-core/templates/prelude.js#L301= I think

[schurhammer]

Thanks inoas :)

We somehow need to get the new Map class into prelude or find a workaround where we don't need to do that. I'm not sure which path to take here. Some options:

1. implement the new Map in prelude instead of stdlib
2. make ther new Map a subclass of the native JS Map, then it should be handled by those code paths in theory
3. support a magic "equals" method, similar to the "inspect" method (prelude.js:283)

[lpil]

3 sounds like it would be useful for other future user implemented data structures as well as this one. Let's go for that one.

I could imagine us in future promoting the JavaScript map implementation into core, but let's be conservative and keep it in the standard library for now.

[lpil]

Beautiful work! I've left some questions

[lpil]

Hey @schurhammer ! I finally got to the bottom of my github inbox now that I'm full time on Gleam 😁

Is this something you would like to continue with?

[lpil]

Incredible work, thank you so much! I am really super impressed and grateful 💜

[lpil]

I've rebase this into main