Resolve gemfile from config in the general case

For example, when using `bundler` via `-rbundler/setup`.

2 files changed, 19 insertions, 2 deletions

diff --git a/lib/bundler/shared_helpers.rb b/lib/bundler/shared_helpers.rb
index 529379ba44..e8f9bfd610 100644
--- a/lib/bundler/shared_helpers.rb
+++ b/lib/bundler/shared_helpers.rb
@@ -237,7 +237,8 @@ module Bundler
     end
 
     def find_gemfile
-      given = ENV["BUNDLE_GEMFILE"]
+      require_relative "../bundler"
+      given = Bundler.settings[:gemfile]
       return given if given && !given.empty?
       find_file(*gemfile_names)
     end
diff --git a/spec/commands/config_spec.rb b/spec/commands/config_spec.rb
index e58a266212..11fdd1ac78 100644
--- a/spec/commands/config_spec.rb
+++ b/spec/commands/config_spec.rb
@@ -518,17 +518,33 @@ end
 
 RSpec.describe "setting gemfile via config" do
   context "when only the non-default Gemfile exists" do
-    it "persists the gemfile location to .bundle/config" do
+    before do
       gemfile bundled_app("NotGemfile"), <<-G
         source "#{file_uri_for(gem_repo1)}"
         gem 'rack'
       G
 
       bundle "config set --local gemfile #{bundled_app("NotGemfile")}"
+    end
+
+    it "persists the gemfile location to .bundle/config" do
       expect(File.exist?(bundled_app(".bundle/config"))).to eq(true)
 
       bundle "config list"
       expect(out).to include("NotGemfile")
     end
+
+    it "gets used when requiring bundler/setup" do
+      bundle :install
+      code = "puts $LOAD_PATH.count {|path| path =~ /rack/} == 1"
+
+      gemfile <<-G
+        source "#{file_uri_for(gem_repo1)}"
+      G
+
+      ruby! code, :env => { "RUBYOPT" => "-r#{lib_dir}/bundler/setup" }, :no_lib => true
+
+      expect(out).to eq("true")
+    end
   end
 end