[rubygems/rubygems] Autoswitch to exact bundler version if present

https://github.com/rubygems/rubygems/commit/bb02953a97

lib/rubygems/bundler_version_finder.rb

@@ -45,6 +45,11 @@ To install the missing version, run `gem install bundler:#{vr.first}`
     return unless bundler_version = self.bundler_version
 
     specs.reject! { |spec| spec.version.segments.first != bundler_version.segments.first }
+
+    exact_match_index = specs.find_index { |spec| spec.version == bundler_version }
+    return specs unless exact_match_index
+
+    specs.unshift(specs.delete_at(exact_match_index))
   end
 
   def self.bundle_update_bundler_version

test/rubygems/test_gem.rb

@@ -341,6 +341,40 @@ class TestGem < Gem::TestCase
     refute_includes e.message, "can't find gem bundler (>= 0.a) with executable bundle"
   end
 
+  def test_activate_bin_path_selects_exact_bundler_version_if_present
+    bundler_latest = util_spec 'bundler', '2.0.1' do |s|
+      s.executables = ['bundle']
+    end
+
+    bundler_previous = util_spec 'bundler', '2.0.0' do |s|
+      s.executables = ['bundle']
+    end
+
+    install_specs bundler_latest, bundler_previous
+
+    File.open("Gemfile.lock", "w") do |f|
+      f.write <<-L.gsub(/ {8}/, "")
+        GEM
+          remote: https://rubygems.org/
+          specs:
+
+        PLATFORMS
+          ruby
+
+        DEPENDENCIES
+
+        BUNDLED WITH
+          2.0.0
+      L
+    end
+
+    File.open("Gemfile", "w") { |f| f.puts('source "https://rubygems.org"') }
+
+    load Gem.activate_bin_path("bundler", "bundle", ">= 0.a")
+
+    assert_equal %w(bundler-2.0.0), loaded_spec_names
+  end
+
   def test_self_bin_path_no_exec_name
     e = assert_raises ArgumentError do
       Gem.bin_path 'a'

test/rubygems/test_gem_bundler_version_finder.rb

@@ -116,7 +116,7 @@ class TestGemBundlerVersionFinder < Gem::TestCase
       assert_equal %w[1 1.0 1.0.1.1], util_filter_specs(specs).map(&:version).map(&:to_s)
     end
     bvf.stub(:bundler_version, v("2.a")) do
-      assert_equal %w[2 2.a 2.0 2.1.1], util_filter_specs(specs).map(&:version).map(&:to_s)
+      assert_equal %w[2.a 2 2.0 2.1.1], util_filter_specs(specs).map(&:version).map(&:to_s)
     end
     bvf.stub(:bundler_version, v("3")) do
       assert_equal %w[3 3.a 3.0 3.1.1], util_filter_specs(specs).map(&:version).map(&:to_s)