Time not implemented on this platform introduced when targeting webassembly

[lat-murmeldjur]

Summary

Using rust libp2p latest master commit as a dependency worked until a few weeks ago, when, "time not implemented on this platform" surfaced as a runtime panic in rust webassembly, solely because of libp2p dependency development.

One safe revision to anchor to seems to be:
055186d

Expected behavior

Just no error when using rust wasm

Actual behavior

"time not implemented on this platform" rutime panic

Relevant log output

Possible Solution

No response

Version

No response

Would you like to work on fixing this bug?

Yes

[elenaf9]

Thanks for the bug report. Would you mind testing which specific commit on master introduced the issue?

[lat-murmeldjur]

Thanks for the bug report. Would you mind testing which specific commit on master introduced the issue?

I would gladly.

After crawling through revisions, the first one that seemed to introduce the issue is:
609dc3b

I can see two types of errors in console from this commit onwards:

weeb_3.js:564 RUST PANIC location=/rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library/std/src/sys/time/unsupported.rs:13:9 payload=time not implemented on this platform

and

.cargo\registry\src\index.crates.io-1949cf8c6b5b557f\js-sys-0.3.95\src\futures\task\singlethread.rs:142:37 payload=RefCell already borrowed

[elenaf9]

Ah, the underlying issue is that future-bounded added support for multiple timer implementations, instead of just a futures-timer-based one. In #6220 we then defaulted to the tokio-based one, which isn't supported on wasm.

To solve this, we can either add cfg flags to handle wasm target family, or switch back to using futures-bounded with the futures-timer timer.

cc @ hanabi1224: any reason for the switch to the tokio-based impl in #6220, or was it just because tokio is our default runtime?