[pdubroy]

I'm not sure I totally understand what you mean by "in-process" here. But you could have some JavaScript that compiles some code in your custom language to WebAssembly and then execute it, and you can use the browser dev tools to set breakpoints the Wasm, inspect the memory, etc.

In the book, we don't cover source maps, but it would also be possible to generate source maps so that you can set breakpoints in (and step through) the original source code in your custom language, rather than debugging at the Wasm instruction level.

Does that answer your question?

[MrResearcher]

Sadly, no, I'd like to write a ~Prolog interpreter (compiler into WASM that would dynamically replace parts of the implementation as source code evolves), and have the debugger and WASM memory inspector as part of the web page written in Javascript, which was used to compiled the code in the first place. That is, would it be possible to implement a debugger and memory inspector in Javascript without resorting to dev tools? Prolog doesn't map 1:1 to WASM/Javscript via source maps, making it nearly impossible to properly debug it in dev tools.

[pdubroy]

Ah, I see! Yeah that's significantly trickier.

re: "dynamically replace parts of the implementation as source code evolves" — there is a technique for this, I have a short write-up on it here: https://github.com/pdubroy/til/blob/main/wasm/2024-02-22-Run...

About the debugging and inspecting —

Inspecting Wasm memory is easy from JS, but to be able to do the debugging, you'd probably either need to rewrite the bytecode (e.g., inserting a call out to JS between every "real" instruction) or a self-hosted interpreter like wasm3 (https://github.com/wasm3/wasm3).

(Or maybe there are better solutions that I'm not thinking of.)