Fedora, ruby 3.1 broken dependencies

[zmiklank]

The build of the app for Fedora and ruby 3.1 is broken.

Reproducer:

1. use following Dockerfile:

FROM quay.io/fedora/ruby-31:latest
ADD app-src ./
RUN bundle install --path ./bundle
CMD exec bundle exec "rackup -P /tmp/rack.pid --host 0.0.0.0 --port 8080"

2. download example app in the same directory where the Dockerfile is:

git clone https://github.com/sclorg/rails-ex.git app-src

3. build the image

docker build --no-cache .

The build fails with:

STEP 1/4: FROM quay.io/fedora/ruby-31:latest
STEP 2/4: ADD app-src ./
--> 7c9e187471c
STEP 3/4: RUN bundle install --path ./bundle
[DEPRECATED] The `--path` flag is deprecated because it relies on being remembered across bundler invocations, which bundler will no longer do in future versions. Instead please use `bundle config set --local path './bundle'`, and stop using this flag
Fetching gem metadata from https://rubygems.org/..........
Resolving dependencies...
Resolving dependencies...

CC @jackorp

[jackorp]

Finally caught the culprit.

bundle install --frozen
[DEPRECATED] The `--frozen` flag is deprecated because it relies on being remembered across bundler invocations, which bundler will no longer do in future versions. Instead please use `bundle config set --local frozen 'true'`, and stop using this flag
Fetching gem metadata from https://rubygems.org/..........
nokogiri-1.12.5-x86_64-linux requires ruby version < 3.1.dev, >= 2.5, which is incompatible with the current version, 3.1.3

So our problem is that nokogiri is resolved to that version. That version specifies < 3.1.dev and both bundler and Rubygems are apparently bad at resolving incompatible Ruby version. We need to get it to stop resolving to the nokogiri with the x86_64-linux suffix...

[jackorp]

JFTR, we have discussed updating dependencies for rails-ex, that does not fix the issue, as Nokogiri still gets resolved the same. Any newer nokogiri drops support for Ruby 2.5, which then is results in unusable app for Ruby 2.5 containers.

I have filed https://bugzilla.redhat.com/show_bug.cgi?id=2178171 as it seems like a behavior regression in the bundler version shipped by Ruby 3.1.3.

What we can do (and probably will until fix comes into relevant Fedora Ruby streams), is either force all Gemfile.lock specified dependencies to use the Ruby platform by calling:
$ bundle config set force_ruby_platform true
Somewhere in tests.

or use a more fine-grained approach by specifying this config on a per-gem basis like so:

gem "nokogiri", :force_ruby_platform => true