Rails server stopped running after omniauth update (breaks devise)

I think this commit fixes the issue you are seeing, unfortunately it will not automatically be pulled into your project through bundle update until devise bumps their version.

So I think you can fix this in the Gemfile with gem 'devise', github: 'heartcombo/devise' (you may need to uninstall the original version first)

And you can verify by using bundle show devise to reveal where the new gem is, go to lib/devise/omniauth.rb, and make sure it opens with the following:

# PATH_TO_DEVISE_GEM/lib/devise/omniauth.rb

# frozen_string_literal: true

begin
  gem "omniauth", ">= 1.0.0"

  require "omniauth"
rescue LoadError
  warn "Could not load 'omniauth'. Please ensure you have the omniauth gem >= 1.0.0 installed and listed in your Gemfile."
  raise
end

What my version had when I ran into this exact same problem yesterday was the following, and this is why it was breaking it for me:

# PATH_TO_OLD_DEVISE_GEM/lib/devise/omniauth.rb

[...]
unless OmniAuth::VERSION =~ /^1./  if Gem::Version.new(OmniAuth::VERSION) < Gem::Version.new('1.0.0')
  raise "You are using an old OmniAuth version, please ensure you have 1.0.0.pr2 version or later installed."     raise "You are using an old OmniAuth version, please ensure you have 1.0.0 version or later installed."
end
[...]