Gem::SpecFetcher#suggest_gems_from_name

# File tmp/rubies/ruby-4.0.0/lib/rubygems/spec_fetcher.rb, line 172
def suggest_gems_from_name(gem_name, type = :latest, num_results = 5)
  gem_name = gem_name.downcase.tr("_-", "")

  # All results for 3-character-or-shorter (minus hyphens/underscores) gem
  # names get rejected, so we just return an empty array immediately instead.
  return [] if gem_name.length <= 3

  max   = gem_name.size / 2
  names = available_specs(type).first.values.flatten(1)

  min_length = gem_name.length - max
  max_length = gem_name.length + max

  gem_name_with_postfix = "#{gem_name}ruby"
  gem_name_with_prefix = "ruby#{gem_name}"

  matches = names.filter_map do |n|
    len = n.name.length
    # If the gem doesn't support the current platform, bail early.
    next unless n.match_platform?

    # If the length is min_length or shorter, we've done `max` deletions.
    # This would be rejected later, so we skip it for performance.
    next if len <= min_length

    # The candidate name, normalized the same as gem_name.
    normalized_name = n.name.downcase
    normalized_name.tr!("_-", "")

    # If the gem is "{NAME}-ruby" and "ruby-{NAME}", we want to return it.
    # But we already removed hyphens, so we check "{NAME}ruby" and "ruby{NAME}".
    next [n.name, 0] if normalized_name == gem_name_with_postfix
    next [n.name, 0] if normalized_name == gem_name_with_prefix

    # If the length is max_length or longer, we've done `max` insertions.
    # This would be rejected later, so we skip it for performance.
    next if len >= max_length

    # If we found an exact match (after stripping underscores and hyphens),
    # that's our most likely candidate.
    # Return it immediately, and skip the rest of the loop.
    return [n.name] if normalized_name == gem_name

    distance = levenshtein_distance gem_name, normalized_name

    # Skip current candidate, if the edit distance is greater than allowed.
    next if distance >= max

    # If all else fails, return the name and the calculated distance.
    [n.name, distance]
  end

  matches = if matches.empty? && type != :prerelease
    suggest_gems_from_name gem_name, :prerelease
  else
    matches.uniq.sort_by {|_name, dist| dist }
  end

  matches.map {|name, _dist| name }.uniq.first(num_results)
end