search_for

# File lib/bundler/resolver.rb, line 101
    def search_for(dependency)
      platform = dependency.__platform
      dependency = dependency.dep unless dependency.is_a? Gem::Dependency
      search = @search_for[dependency] ||= begin
        index = index_for(dependency)
        results = index.search(dependency, @base[dependency.name])

        if vertex = @base_dg.vertex_named(dependency.name)
          locked_requirement = vertex.payload.requirement
        end

        if !@prerelease_specified[dependency.name] && (!@use_gvp || locked_requirement.nil?)
          # Move prereleases to the beginning of the list, so they're considered
          # last during resolution.
          pre, results = results.partition {|spec| spec.version.prerelease? }
          results = pre + results
        end

        spec_groups = if results.any?
          nested = []
          results.each do |spec|
            version, specs = nested.last
            if version == spec.version
              specs << spec
            else
              nested << [spec.version, [spec]]
            end
          end
          nested.reduce([]) do |groups, (version, specs)|
            next groups if locked_requirement && !locked_requirement.satisfied_by?(version)
            spec_group = SpecGroup.new(specs)
            spec_group.ignores_bundler_dependencies = @allow_bundler_dependency_conflicts
            groups << spec_group
          end
        else
          []
        end
        # GVP handles major itself, but it's still a bit risky to trust it with it
        # until we get it settled with new behavior. For 2.x it can take over all cases.
        if !@use_gvp
          spec_groups
        else
          @gem_version_promoter.sort_versions(dependency, spec_groups)
        end
      end
      search.select {|sg| sg.for?(platform) }.each {|sg| sg.activate_platform!(platform) }
    end