strip debug info from generated wasm if minify is true

[AurelienRichez]

↪️ Pull Request

Disclaimer : I am not a wasm or rust expert.

I tinkered with parceljs, and managed to reduce the generated wasm file from 1.6MB to 116B for the usuall add example.

After trying to compile rust code with parcel, I noticed that the wasm file was really big ( #3235 shows the problem). More than 1.5MB 😨. Using twiggy shows that it is essentially bloat from debugs symbols.

I tried to figure out how wasm-pack optimize wasm and then tried different solutions to shrink the size on the simple add.rs file :

• -Copt-level=s (should optimize for size): no visible effect, but it makes sense for such a simple function
• -Clto=thin: it reduced the size to 44kB A big win but still a lot for a simple add function. It seems some debug symbol are still there
• -Cdebuginfo=0 (should remove debug info): no visible effect, so I may have misunderstood this option.
• -Clink-arg=-s (option passed to the linker to strip the binary): it reduced the size to 116B.

As a result I kept the last one (-Clto=thin did not show any difference once -Clink-arg=-s is added) . It is difficult to know if the others are useful for a more complicated case. I tried this on a mac.

I think wasm-pack actually uses wasm-opt to do this, so this might be another way to do it.

💻 Examples

For reference, the rust code used.
add.rs :

#[no_mangle]
pub fn add(a: i32, b: i32) -> i32 {
  return a + b
}

building with parcel version 1.12.4 :

✨  Built in 669ms.

dist/add.wasm    ⚠️  1.65 MB    615ms 

building with --no-cache with the modified version :

✨  Built in 502ms.

dist/add.wasm    116 B    448ms

🚨 Test instructions

I did not add unit tests for this (this is not really a bug). A good way to test this would be to compile the rust function mentionned above by calling parcel (or repo mentionned in #3235).

✔️ PR Todo

• Added/updated unit tests for this change
• Filled out test instructions (In case there aren't any unit tests)
• Included links to related issues/PRs

[DeMoorJasper]

This looks amazing.

Not entirely sure if we'll merge this as Parcel 1 is currently not really receiving any more updates.
Even if this doesn't end up in Parcel 1 it will definitely be an big help when implementing Rust for Parcel 2