Build: support Ruby under build.tools

[humitos]

We should add support for Ruby on build.tools. It will be useful for doctools like Jekyll.

Work required:

• Update the documentation
• Install asdf-ruby (https://github.com/asdf-vm/asdf-ruby) on Docker images
• Compile latest Ruby version and upload it S3 (happening at https://app.circleci.com/pipelines/github/readthedocs/readthedocs-docker-images/289/workflows/f1bc7c62-02d8-4353-ac94-972eb58b0675/jobs/503)
• Update settings.py to add this tool and version
• Update config v2 to accept this value
• Create a branch on test-builds for this use case

Note: we had a support request for this at #9599 (comment)

[humitos]

I note there are other people installing Julia as well in a pretty weird form. We should probably document how to install any tool supported by asdf in an easy way. The process is like:

build:
  commands:
    - asdf plugin add <tool> <asdf plugin url>
    - asdf install <tool> <version>
    - asdf global <tool> <version>

Users should be able to do this without our intervention. However, for those tools that require to be compiled or are heavy in network transfer, we should probably include them in our S3 cache.

[henryiii]

FYI, this (storing in S3) would save 379s. 89s to compile the required modules for Jekyll would remain. I’d be fine with only a recent (3.2 or 3.1 ruby) cached.

[Jasha10]

Note to future travelers: using the build.command key as mentioned above will result in readthedocs' pre-defined process being entirely overridden.

If you just want to extend the build with additional steps, the following may be more appropriate:

build:
  jobs:
    post_system_dependencies
      - asdf plugin add <tool> <asdf plugin url>
      - asdf install <tool> <version>
      - asdf global <tool> <version>

[humitos]

I added support for Ruby 3.3.x in our build images. I tested it locally and it worked fine. This work will be deployed next Tuesday, and I'd love to heard some feedback from people already using "the hacky way" 🙏🏼

Now, Ruby is available under the normal build.tools configuration option:

build:
  tools:
    ruby: "3.3"

This will use a pre-compiled version of Ruby, making the builds to build faster.

[henryiii]

deployed next Tuesday

So we should try it out after Tuesday, it's not something we can try out quite yet?

[humitos]

Yes, after Tuesday. It's not deployed yet. I will write something here when it's deployed, so everybody is aware.

[humitos]

We just deployed this change. Ruby 3.3 is now available on Read the Docs 🎉

[henryiii]

Before: Build took 408 seconds
After: Build took 49 seconds

🎉

Also, a lot simpler:

 build:
   os: ubuntu-22.04
+
+  tools:
+    ruby: "3.3"
 
   commands:
-    - asdf plugin add ruby https://github.com/asdf-vm/asdf-ruby.git
-    - asdf install ruby 3.1.2
-    - asdf global ruby 3.1.2
-    - gem install bundler
-    - bundle config set --local deployment 'true'
-    - bundle config set --local without development
     - bundle install
     - >
       JEKYLL_ENV=production bundle exec jekyll build --destination
       _readthedocs/html --baseurl $(echo -n "$READTHEDOCS_CANONICAL_URL" | cut
       -d '/' -f 4-)

[humitos]

@henryiii thanks for sharing your feedback! I'm happy the UX got improved with this feature 💯