Allow WASM to use unsupported backend with JS feature disabled

[Worldwidebrine]

I'm trying to do something using WASM.
getrandom is required by a crate I need, but I am sure I am not going to invoke anything calling getrandom indirectly.

I get some strange JS imports about error handling, although I never want or need any.

I tried using the unsupported backend to get rid of it, but it turned out that as long as I enable JS feature, those imports will be generated, even if I'm using unsupported backend.

And cargo build just fails if JS feature is not enabled.

[newpavlov]

I tried using the unsupported backend to get rid of it, but it turned out that as long as I enable JS feature, those imports will be generated, even if I'm using unsupported backend.

If you don't want the JS stuff, why do you enable the feature?

Problems and confusion like this is why I argued that we should remove the wasm_js support completely and replace it with #725, but @dhardy and @josephlr decided otherwise.

[Worldwidebrine]

If you don't want the JS stuff, why do you enable the feature?

edited

And cargo build just fails if JS feature is not enabled.

[newpavlov]

If you do not rely on JS, you should select an opt-in backend using getrandom_backend configuration flag.

Closing since it works as intended.

[Worldwidebrine]

Thank you for reminding me that I've tried custom backend to always return error, and the function has been kept after I enable JS feature getting cargo build normal. Now after deleting my custom impl, those JS code are gone.

These JS imports, I guess, come from getrandom::Error in returning type Result. I didn't export my custom impl, no idea why custom impl was exported from Rust to JS

[josephlr]

@Worldwidebrine does that mean
--cfg getrandom_backend="unsupported"
is working for you as expected?

[Worldwidebrine]

@josephlr

does that mean
--cfg getrandom_backend="unsupported"
is working for you as expected?

Yes, but no about the issue title. I still have to manually add getrandom with JS feature to cargo.toml in order to get my dependency compiled normally.