Allow keeping debug symbols in the generated wasm output in release builds

[jbg]

We're currently looking at improving error reporting from some WebAssembly running in the browser, and we're having trouble getting trunk to produce a .wasm file that includes DWARF debug info. We want to be able to split off that debug info, store it, and use it to symbolicate any reported errors.

Setting debug = true in the release profile in Cargo.toml isn't sufficient because wasm-bindgen-cli strips the debug info when run in release mode unless --keep-debug is passed.

I guess eventually it would be cool if trunk could (optionally) split off the debug info itself and output it separately, but for now it would be sufficient if there was a way to get --keep-debug passed to wasm-bindgen-cli (somewhere around here) and then we can separately run wasm-split afterwards.

[thedodd]

@jbg that's a good idea. We can actually just add a new option to the Rust asset type pipeline type. Folks would then be able to do something like: <link data-trunk rel="rust" data-keep-debug/>, and then when such an option is specified, we would just pass along the --keep-debug option to wasm-bindgen-cli.

This should be quite simple to add to the pipeline. If you are interested in contributing a PR, that would be excellent. That would get you 90% of the way there. That last bit would be to add some tooling around wasm-split and where to output the debug symbols &c. That could all be passed along as data-* options in the HTML link as well.

[jbg]

Cool, sounds like a good approach. I'll take a stab at it tomorrow.

[thedodd]

It really seems as though this would be a perfect use case for the plugin system (the wasm-split aspect of this). Especially given that wasm-split does not yet ship pre-compiled, so folks are expected to build it on their own. A plugin for this would be perfect as it is somewhat niche.