Add metric for tracking BUNDLED WITH existence (heroku#1707)

Track apps with and without `BUNDLED WITH` in the `Gemfile.lock`. This will show how many apps are using the default bundler version.

Author: schneems

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 ## [Unreleased]
 
+- Add metric: Track apps with and without `BUNDLED WITH` in the `Gemfile.lock`
 
 ## [v345] - 2026-01-26
 

lib/language_pack/helpers/gemfile_lock.rb

@@ -89,6 +89,8 @@ def initialize(contents:, report: HerokuBuildReport::GLOBAL)
             @empty = true
             @version = nil
           end
+
+          report.capture("gemfile_lock.bundled_with.empty" => @empty)
         end
 
         def empty?

spec/helpers/gemfile_lock_spec.rb

@@ -15,7 +15,7 @@
 
     expect(gemfile_lock.bundler.version).to eq(nil)
     expect(gemfile_lock.bundler.empty?).to eq(true)
-    expect(report.data).to be_empty
+    expect(report.data).to eq({"gemfile_lock.bundled_with.empty" => true})
   end
 
   it "records invalid parsing" do

spec/helpers/heroku_ruby_installer_spec.rb

@@ -82,7 +82,8 @@ def ruby_version
             "ruby_version_major_minor" => "3.5",
             "ruby_version_full" => "3.5.0.preview1",
             "ruby_version_origin" => "Gemfile.lock",
-            "ruby_version_unique" => "ruby-3.5.0.preview1"
+            "ruby_version_unique" => "ruby-3.5.0.preview1",
+            "gemfile_lock.bundled_with.empty" => true
           }
 
           expect(sort_hash(report.data)).to eq(sort_hash(expected))
@@ -121,7 +122,8 @@ def ruby_version
             "jruby_version_major_minor" => "9.4",
             "jruby_version_ruby_version" => "3.1.4",
             "ruby_version_origin" => "Gemfile.lock",
-            "ruby_version_unique" => "ruby-3.1.4-jruby-9.4.9.0"
+            "ruby_version_unique" => "ruby-3.1.4-jruby-9.4.9.0",
+            "gemfile_lock.bundled_with.empty" => true
           }
 
           expect(sort_hash(report.data)).to eq(sort_hash(expected))