Fix Bundler that re-exec $0 when a version is present in the config:

bundler/spec/runtime/self_management_spec.rb

@@ -171,6 +171,24 @@
       expect(out).to eq(previous_minor)
     end
 
+    it "requires the right bundler version from the config and run bundle CLI without re-exec" do
+      unless Bundler.rubygems.provides?(">= 4.1.0.dev")
+        skip "This spec can only run when Gem::BundlerVersionFinder.bundler_versions reads bundler configs"
+      end
+
+      lockfile_bundled_with(current_version)
+
+      bundle "config set --local version #{previous_minor}"
+      bundle "config set --local path.system true"
+      bundle "install"
+
+      script = bundled_app("script.rb")
+      create_file(script, "p 'executed once'")
+
+      bundle "-v", env: { "RUBYOPT" => "-r#{script}" }
+      expect(out).to eq(%("executed once"\n9.3.0))
+    end
+
     it "does not try to install when using bundle config version global" do
       lockfile_bundled_with(previous_minor)
 

lib/rubygems/bundler_version_finder.rb

@@ -10,6 +10,8 @@ def self.bundler_version
     v ||= bundle_update_bundler_version
     return if v == true
 
+    v ||= bundle_config_version
+
     v ||= lockfile_version
     return unless v
 
@@ -49,21 +51,7 @@ def self.lockfile_version
   private_class_method :lockfile_version
 
   def self.lockfile_contents
-    gemfile = ENV["BUNDLE_GEMFILE"]
-    gemfile = nil if gemfile&.empty?
-
-    unless gemfile
-      begin
-        Gem::Util.traverse_parents(Dir.pwd) do |directory|
-          next unless gemfile = Gem::GEM_DEP_FILES.find {|f| File.file?(f) }
-
-          gemfile = File.join directory, gemfile
-          break
-        end
-      rescue Errno::ENOENT
-        return
-      end
-    end
+    gemfile = gemfile_path
 
     return unless gemfile
 
@@ -82,19 +70,24 @@ def self.lockfile_contents
   private_class_method :lockfile_contents
 
   def self.bundle_config_version
-    config_file = bundler_config_file
-    return unless config_file && File.file?(config_file)
+    version = nil
 
-    contents = File.read(config_file)
-    contents =~ /^BUNDLE_VERSION:\s*["']?([^"'\s]+)["']?\s*$/
+    [bundler_local_config_file, bundler_global_config_file].each do |config_file|
+      next unless config_file && File.file?(config_file)
 
-    $1
+      contents = File.read(config_file)
+      contents =~ /^BUNDLE_VERSION:\s*["']?([^"'\s]+)["']?\s*$/
+
+      version = $1
+      break if version
+    end
+
+    version
   end
   private_class_method :bundle_config_version
 
-  def self.bundler_config_file
-    # see Bundler::Settings#global_config_file and local_config_file
-    # global
+  def self.bundler_global_config_file
+    # see Bundler::Settings#global_config_file
     if ENV["BUNDLE_CONFIG"] && !ENV["BUNDLE_CONFIG"].empty?
       ENV["BUNDLE_CONFIG"]
     elsif ENV["BUNDLE_USER_CONFIG"] && !ENV["BUNDLE_USER_CONFIG"].empty?
@@ -103,10 +96,36 @@ def self.bundler_config_file
       ENV["BUNDLE_USER_HOME"] + "config"
     elsif Gem.user_home && !Gem.user_home.empty?
       Gem.user_home + ".bundle/config"
-    else
-      # local
-      "config"
     end
   end
-  private_class_method :bundler_config_file
+  private_class_method :bundler_global_config_file
+
+  def self.bundler_local_config_file
+    gemfile = gemfile_path
+    return unless gemfile
+
+    File.join(File.dirname(gemfile), ".bundle", "config")
+  end
+  private_class_method :bundler_local_config_file
+
+  def self.gemfile_path
+    gemfile = ENV["BUNDLE_GEMFILE"]
+    gemfile = nil if gemfile&.empty?
+
+    unless gemfile
+      begin
+        Gem::Util.traverse_parents(Dir.pwd) do |directory|
+          next unless gemfile = Gem::GEM_DEP_FILES.find {|f| File.file?(f) }
+
+          gemfile = File.join directory, gemfile
+          break
+        end
+      rescue Errno::ENOENT
+        return
+      end
+    end
+
+    gemfile
+  end
+  private_class_method :gemfile_path
 end

test/rubygems/test_gem_bundler_version_finder.rb

@@ -66,7 +66,7 @@ def test_bundler_version_with_bundle_config
       f.write(config_content)
       f.flush
 
-      bvf.stub(:bundler_config_file, f.path) do
+      bvf.stub(:bundler_global_config_file, f.path) do
         assert_nil bvf.bundler_version
       end
     end
@@ -81,7 +81,7 @@ def test_bundler_version_with_bundle_config_single_quoted
       f.write(config_with_single_quoted_version)
       f.flush
 
-      bvf.stub(:bundler_config_file, f.path) do
+      bvf.stub(:bundler_global_config_file, f.path) do
         assert_nil bvf.bundler_version
       end
     end
@@ -98,18 +98,33 @@ def test_bundler_version_with_bundle_config_version
       f.write(config_content)
       f.flush
 
-      bvf.stub(:bundler_config_file, f.path) do
+      bvf.stub(:bundler_global_config_file, f.path) do
         assert_equal v("1.1.1.1"), bvf.bundler_version
       end
     end
   end
 
   def test_bundler_version_with_bundle_config_non_existent_file
-    bvf.stub(:bundler_config_file, "/non/existent/path") do
+    bvf.stub(:bundler_global_config_file, "/non/existent/path") do
       assert_nil bvf.bundler_version
     end
   end
 
+  def test_bundler_version_set_on_local_config
+    config_content = <<~CONFIG
+      BUNDLE_VERSION: "1.2.3"
+    CONFIG
+
+    Tempfile.create("bundle_config") do |f|
+      f.write(config_content)
+      f.flush
+
+      bvf.stub(:bundler_local_config_file, f.path) do
+        assert_equal v("1.2.3"), bvf.bundler_version
+      end
+    end
+  end
+
   def test_bundler_version_with_bundle_config_without_version
     config_without_version = <<~CONFIG
       BUNDLE_JOBS: "8"
@@ -120,7 +135,7 @@ def test_bundler_version_with_bundle_config_without_version
       f.write(config_without_version)
       f.flush
 
-      bvf.stub(:bundler_config_file, f.path) do
+      bvf.stub(:bundler_global_config_file, f.path) do
         assert_nil bvf.bundler_version
       end
     end