Add custom rust toolchain support

[fewensa]

• Update follow Add wasm32-unknown-unknown component for override toolchain paritytech/srtool#68

[chevdor]

Custom RUSTC_VERSION

Picking the RUSTC_VERSION is not implemented in srtool-actions on purpose.

The idea of fetching the canonical version from https://raw.githubusercontent.com/${{ inputs.image }}/master/RUSTC_VERSION is to ensure that all users use the same canonicial version so that any user can check any runtime without having to worry about what srtool to use. It has its short-comings and having the information of the RUSTC_VERSION in the runtime itself is an option I am considering.

At the moment, If you start building your runtime with something else than the canocial version, the checks will fail and the users of your runtime will wonder what the problem is.

Could you explain what your use case is ?

[fewensa]

Two reasons.

1. not all like substrate projects use same rust toolchain with substrate/polkadot
2. because of you published docker image tag named semantic style version. but some project use date named version number. https://github.com/darwinia-network/darwinia/blob/3b4dbf996945f1b5237fd5834c0cc38cbc446ceb/rust-toolchain.toml#L2

and srtool build in runtime directory, so can not read root directory rust-toolchain.toml file do override rust toolchain (I tested it's not work). so hopefully srtool can set rustc_version

[chevdor]

not all like substrate projects use same rust toolchain with substrate/polkadot

Ok, fair enough. substrate/polkadot use the latest stable. it should be a goal to get there. It is possible since recently and you should really aim for that.

because of you published docker image tag named semantic style version

This is mainly for users to find they way around since currently, they will not have an easy way to know when you built your runtimes.

and srtool build in runtime directory, so can not read root directory rust-toolchain.toml file do override rust toolchain (I tested it's not work)

This is blocked on purpose yes

Let me think how we can solve your problem without comprising too much for the users.

[AurevoirXavier]

This is blocked on purpose yes

Let me think how we can solve your problem without comprising too much for the users.

Currently, I am using a soft link to resolve this issue.

[AurevoirXavier]

Hey @chevdor, any feedback?

[chevdor]

I am not completely happy with the raw solution as it is really a foot gun.

Nothing against the PR, my main concern is related to users trying to verify runtimes. With this PR in, once the feature is used to build runtimes, those will appear "invalid" unless users can find and use the right version.

I have some ideas how to fix that cleanly but that still requires testing.

[AurevoirXavier]

I am not completely happy with the raw solution as it is really a foot gun.

Sorry, I mean this.

Currently, I am using a soft link to resolve this issue.

I think maybe we can close this PR.

[chevdor]

It would be nice to hear from @fewensa whether your "outlaw" solution 😄 is an acceptable workaround.

[fewensa]

I still hope to be implemented by srtool-actions, because this is more general. of course softlink it's works for me