[bug] Javascript Logical OR operator throws SyntaxError

[lnfel]

Describe the bug

Trying out Tauri 2.x RC with sveltekit 2.x and it seems failing to recognize Logical OR ||= operator in JavaScript.

This is the exact line of code in sveltekit repo that throws an error when running pnpm tauri dev:
https://github.com/sveltejs/kit/blob/45cb8c5f305b4d9e61a32e19af8059dc0da4c255/packages/kit/src/runtime/client/client.js#L305

According to the author, it is valid JavaScript:
sveltejs/kit#12040

As seen on MDN docs:
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Logical_OR_assignment

I have another tauri project that uses sveltekit 1.x, they have pending_invalidate = pending_invalidate || Promise.resolve(); in it but in 2.x they changed it to await (pending_invalidate ||= Promise.resolve());.

Not sure whether the issue is with tauri, wry or tao, it would be nice if someone can help.

Reproduction

https://github.com/lnfel/tauri2.xrc-svelte5

Expected behavior

Expected the JavaScript logical OR operator ||= to be a valid syntax.

Full tauri info output

[✔] Environment
    - OS: Mac OS 10.15.7 X64
    ✔ Xcode Command Line Tools: installed
    ✔ rustc: 1.80.1 (3f5fd8dd4 2024-08-06)
    ✔ cargo: 1.80.1 (376290515 2024-07-16)
    ✔ rustup: 1.27.1 (54dd3d00f 2024-04-24)
    ✔ Rust toolchain: stable-x86_64-apple-darwin (default)
    - node: 22.6.0
    - pnpm: 8.6.3
    - npm: 10.8.2
    - bun: 1.0.14

[-] Packages
    - tauri [RUST]: 2.0.0-rc.6
    - tauri-build [RUST]: 2.0.0-rc.6
    - wry [RUST]: 0.42.0
    - tao [RUST]: 0.29.1
    - @tauri-apps/api [NPM]: 2.0.0-rc.3
    - @tauri-apps/cli [NPM]: 2.0.0-rc.7

[-] App
    - build-type: bundle
    - CSP: unset
    - frontendDist: ../build
    - devUrl: http://localhost:5173/
    - framework: Svelte
    - bundler: Vite

Stack trace

Stack trace is seen on tauri app window by opening devtools (alt + cmd + i on macOS):

Unhandled Promise Rejection: SyntaxError: Unexpected token '='
    (anonymous function) - client.js:305
    promiseReactionJob

### Additional context

_No response_

[Legend-Master]

I'm not the most familiar with mac but from your system information, Mac OS 10.15.7 comes with webkit 608 which corresponding to safari 13, and ||= is added in safari 14

[lnfel]

I'm not the most familiar with mac but from your system information, Mac OS 10.15.7 comes with webkit 608 which corresponding to safari 13, and ||= is added in safari 14

I don't quite understand yet, does this mean Tauri/Wry uses the webkit version that comes with my macOS version. Resulting to the issue since ||= is not available yet. My other projects that uses sveltekit 2.x are working fine when running on chrome browser, I guess they have their own bundle of webkit? The only issue I have is when running sveltekit 2.x with tauri.

Is there a possible work-around on this issue or I am stuck? I've been hoping to build cross platform apps using tauri...

Maybe I can run a script that changes a specific code on sveltekit package before running tauri dev/build? I have no longer any capabilities to update my device so getting updates on Safari is out of the picture.

[Legend-Master]

Tauri uses the webview (in this case webkit on macos) provided by the OS, for your case, you can try changing build.target to something like es2020 in vite config

[lnfel]

I got the build release working after adding es2020 as build target but pnpm tauri dev still points to the sveltekit pnpm package that has the ||= operator.

[Legend-Master]

Try esbuild: { target: 'es2020' } in vite config?

[lnfel]

Try esbuild: { target: 'es2020' } in vite config?

Tried it, no transformation happens during dev start, the target option might only be available during build. I overwritten the code directly and it now works. This is obviously not the correct way to do it but the build release is working fine so I will go with this for now.

[Legend-Master]

Some people suggested using optimizeDeps.esbuildOptions.target instead, maybe give it a shot?

vitejs/vite#13756

[Legend-Master]

I'm closing this for now since it's not really a problem that tauri can fix, feel free to keep the conversation going though