Lighther "prefer gems.rb" deprecation

The previous logic is unclear to me. It seemed to try to detect only
"multiple gemfile situations", but it was doing it incorrectly, I think.

The new message is printed _only_ if both gems.rb and Gemfile are
detected in the same project. And recommends sticking with gems.rb. But
we are not yet deprecating "Gemfile" other than that.

2 files changed, 38 insertions, 8 deletions

diff --git a/lib/bundler/shared_helpers.rb b/lib/bundler/shared_helpers.rb
index 996f7b3fd4..0f4f54dced 100644
--- a/lib/bundler/shared_helpers.rb
+++ b/lib/bundler/shared_helpers.rb
@@ -157,11 +157,16 @@ module Bundler
       multiple_gemfiles = search_up(".") do |dir|
         gemfiles = gemfile_names.select {|gf| File.file? File.expand_path(gf, dir) }
         next if gemfiles.empty?
-        break false if gemfiles.size == 1
+        break gemfiles.size != 1
       end
-      return unless multiple_gemfiles && Bundler.bundler_major_version == 1
-      Bundler::SharedHelpers.major_deprecation 2, \
-        "gems.rb and gems.locked will be preferred to Gemfile and Gemfile.lock."
+      return unless multiple_gemfiles
+      diagnosis = "Multiple gemfiles (gems.rb and Gemfile) detected."
+      advice = if Bundler.feature_flag.prefer_gems_rb?
+        "Make sure you remove Gemfile and Gemfile.lock since bundler is ignoring them in favor of gems.rb and gems.rb.locked."
+      else
+        "The gems.rb and gems.rb.locked files are currently ignored, but they will get used as soon as you delete your Gemfile and Gemfile.lock files."
+      end
+      Bundler.ui.warn [diagnosis, advice].join(" ")
     end
 
     def trap(signal, override = false, &block)
diff --git a/spec/other/major_deprecation_spec.rb b/spec/other/major_deprecation_spec.rb
index 8aa6005529..ae9253fef5 100644
--- a/spec/other/major_deprecation_spec.rb
+++ b/spec/other/major_deprecation_spec.rb
@@ -82,15 +82,32 @@ RSpec.describe "major deprecations" do
       expect(warnings).not_to have_major_deprecation
     end
 
-    xit "should print a Gemfile deprecation warning" do
+    it "should print a proper warning when both gems.rb and Gemfile present, and use Gemfile", :bundler => "< 2" do
       create_file "gems.rb"
       install_gemfile! <<-G
         source "file://#{gem_repo1}"
         gem "rack"
       G
+
+      expect(warnings).to include(
+        "Multiple gemfiles (gems.rb and Gemfile) detected. The gems.rb and gems.rb.locked files are currently ignored, but they will get used as soon as you delete your Gemfile and Gemfile.lock files."
+      )
+
       expect(the_bundle).to include_gem "rack 1.0"
+    end
+
+    it "should print a proper warning when both gems.rb and Gemfile present, and use gems.rb", :bundler => "2" do
+      create_file "gems.rb"
+      install_gemfile! <<-G
+        source "file://#{gem_repo1}"
+        gem "rack"
+      G
 
-      expect(warnings).to have_major_deprecation a_string_including("gems.rb and gems.locked will be preferred to Gemfile and Gemfile.lock.")
+      expect(warnings).to include(
+        "Multiple gemfiles (gems.rb and Gemfile) detected. Make sure you remove Gemfile and Gemfile.lock since bundler is ignoring them in favor of gems.rb and gems.rb.locked."
+      )
+
+      expect(the_bundle).not_to include_gem "rack 1.0"
     end
 
     context "with flags" do
@@ -126,8 +143,16 @@ RSpec.describe "major deprecations" do
       RUBY
     end
 
-    it "should print a single deprecation warning" do
-      expect(warnings).to have_major_deprecation("gems.rb and gems.locked will be preferred to Gemfile and Gemfile.lock.")
+    it "should print a single deprecation warning", :bundler => "< 2" do
+      expect(warnings).to include(
+        "Multiple gemfiles (gems.rb and Gemfile) detected. The gems.rb and gems.rb.locked files are currently ignored, but they will get used as soon as you delete your Gemfile and Gemfile.lock files."
+      )
+    end
+
+    it "should print a single deprecation warning", :bundler => "2" do
+      expect(warnings).to include(
+        "Multiple gemfiles (gems.rb and Gemfile) detected. Make sure you remove Gemfile and Gemfile.lock since bundler is ignoring them in favor of gems.rb and gems.rb.locked."
+      )
     end
   end