Cargo emits "error: Unrecognized option: 'json'" error beginning ~ 07/2019, consider option to bisect rustc directly without Cargo

[chrissimpkins]

From the conversation of a cargo-bisect-rustc ICE analysis in rust-lang/rust#69096 (comment) where the error message error: Unrecognized option: 'json' occurred as of the 2019-07-30 nightly.

@eddyb said:

That suggests that you're using a Cargo too new or somehow back-compat logic was removed (or never present?) in Cargo (not sure what our policy is).

You need an older Cargo to go back past the addition of --json.

But also it would be nice if Cargo didn't need to be involved in the bisection process, because it IMO unnecessarily complicates it.

cargo 1.41.0 (626f0f40e 2019-12-03)
release: 1.41.0
commit-hash: 626f0f40efd32e6b3dbade50cd53fdfaa08446ba
commit-date: 2019-12-03

cargo 1.43.0-nightly (3c53211c3 2020-02-07)
release: 1.43.0
commit-hash: 3c53211c3d7fee4f430f170115af5baad17a3da9
commit-date: 2020-02-07

[eddyb]

Specifically in this case, the testcase is just one file and should reproduce with just rustc, I think we should have the option to bisect rustc directly without Cargo.

[lqd]

You don't have to use cargo: you can bisect using the --script flag to point at a custom script triggering the behaviour you need, e.g. calling rustc directly.

[chrissimpkins]

I opened #47 with a few script extensions and it sounds like the consensus is that much of this functionality belongs in the tool rather than as extensions through scripts. I can close this if it seems like an appropriate area for scripting.