Rubygems introduced a file option to specify Ruby version in Gemfile

We add ruby version in the Gemfile or in the .ruby-version files. This ensures that the application runs on the correct version of Ruby.

In case of version mismatch bundler throws an error.

Your Ruby version is 3.1.0, but your Gemfile specified 3.2.2

Before

We needed to add the ruby version in the Gemfile so the bundler uses correct ruby version or warns if incorrect ruby version is in use.

.ruby-version file is used by tools like rvm or rbenv to switch the ruby version.

Gemfile

source 'https://rubygems.org'

ruby 3.2.2

.ruby-version

3.2.2

The problem with this approach is that we have to update the version in both the files.

After

Rubygems introduced a :file option that can read the Ruby version from a file.

Now its easier as we have to just update the version in the .ruby-version file and the Gemfile will automatically read the version.

Gemfile

source 'https://rubygems.org'

ruby file: '.ruby-version'

.ruby-version

3.2.2

NOTE: Ensure you’re on bundler 2.5.1 or above and rubygems 3.4.20 and above.

# Update rubygems and bundler if required
gem update --system
gem -v

bundle update --bundler
bundle -v

How this works?

• The method checks if :file option is provided
• Check if both :file option as well as the ruby version is provided and raise an error (Only one is required)

ruby 3.2.2, file: '.ruby-version' # ❌ This will raise an error

ruby 3.2.2                        # ✅

ruby file: '.ruby-version'        # ✅

• Read the ruby version from the file name provided with :file option
• normalize the version string

Acceptable version strings are:

3.2.2
ruby-3.2.2
ruby   3.2.2

References