How can I specify the rust toolchain?

[nathan-at-least]

I have hit this nightly-specific error while installing mdbook, so the simplest work-around I would like to try is installing mdbook with cargo stable.

I didn't see any input option for selecting a toolchain. I tried setting the ambient default in a step prior to using this action, ala:

steps:                                                                                                                         
  - name: Select rust stable                                                                                                                                                   
    run: rustup default stable                                                                                                                                                 
  - uses: taiki-e/cache-cargo-install-action@v1                                                                                                                                
    with:                                                                                                                                                                      
      tool: mdbook@0.4.19

-however I run into the same error.

Questions:

• Is there a way to verify which toolchain is used in the action?
• Is there a way to specify the stable toolchain?

[taiki-e]

This action uses the current default toolchain. So, cargo -vV and rustc -vV should show the toolchain currently in use.

Also, (as documented) it is recommended to use install-action instead of this action for tools that are supported by install-action, such as mdbook. It is more robust against such compiler bugs.