Gem::Resolver#search_for

# File tmp/rubies/ruby-3.1.3/lib/rubygems/resolver.rb, line 227
def search_for(dependency)
  possibles, all = find_possible(dependency)
  if !@soft_missing && possibles.empty?
    @missing << dependency
    exc = Gem::UnsatisfiableDependencyError.new dependency, all
    exc.errors = @set.errors
    raise exc
  end

  groups = Hash.new {|hash, key| hash[key] = [] }

  # create groups & sources in the same loop
  sources = possibles.map do |spec|
    source = spec.source
    groups[source] << spec
    source
  end.uniq.reverse

  activation_requests = []

  sources.each do |source|
    groups[source].
      sort_by {|spec| [spec.version, spec.platform =~ Gem::Platform.local ? 1 : 0] }.
      map {|spec| ActivationRequest.new spec, dependency }.
      each {|activation_request| activation_requests << activation_request }
  end

  activation_requests
end