Builds: Bundler version from Gemfile.lock now installed and used

Features Updates
1

The Bundler version specified in the BUNDLED_WITH section of your Gemfile.lock file is now automatically installed and used to install the gems from your Gemfile. If you’ve been previously advised to change your Gemfile.lock to specify an older version of Bundler such as 2.0.1, that workaround is no longer necessary. See also respect "BUNDLED WITH" in Gemfile.lock to set bundler version · Issue #296 · netlify/build-image · GitHub.

2

If your site is set to use a Ruby version older than 2.3.0 and you have no Gemfile.lock (or your Gemfile.lock specifies a version of bundler that is 2.0.0 or greater), you may encounter a build failure with the message “bundler requires Ruby version >= 2.3.0”. While we plan to fix this, you can get it working right now with one of two methods:

  1. Make your build use a newer Ruby version by setting the RUBY_VERSION environment variable in the Netlify UI to 2.3.0 or any newer version.
  2. Add a Gemfile.lock created by a bundler version that is older than 2.0.0. To specify the version of bundler to run, install the desired bundler version then run bundle with the version surrounded by underscores as the first argument. For instance, to create a Gemfile.lock using bundler version 1.17.3, run gem install bundler:1.17.3 then run bundle _1.17.3_ lock.

See also Bundler install fails when Ruby version is less than 2.3.0 and no Gemfile.lock specifying Bundler 1 is present · Issue #356 · netlify/build-image · GitHub.