Deno: Idle REPL uses CPU instead of actually idling

[solson]

When I open the REPL in Deno 1.4.3, the Deno process stays at 100% CPU usage (and I can hear my fans spin up), while Deno 1.4.2 actually idles at 0%.

Version info: https://github.com/denoland/deno/commit/e5348a6a38b3c06a916223ad0b99e8cfe47725b1 with cargo build --release

cc @caspervonb

[ry]

Confirmed - I get 100% CPU sitting in REPL.

[solson]

I figured out that line 450 here is waking up constantly, but I don't yet know why:

https://github.com/denoland/deno/blob/4c7f53b04bc631525a4512576fc0d7dca05dec09/cli/main.rs#L445-L452