Add a v2 compact index artifice and cover cooldown end-to-end

A `CompactIndexCooldownAPI` subclass overrides `build_gem_version` to
emit `CompactIndex::GemVersionV2` with `created_at` sourced from
`spec.date`, letting tests carry a deterministic timestamp per built
gem. `spec/install/cooldown_spec.rb` exercises the source DSL keyword,
`--cooldown` flag, `BUNDLE_COOLDOWN`, `bundle config set cooldown`,
the rolling-delay filter, the lockfile bypass, and the CLI vs Gemfile
precedence against the new artifice.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: hsbt

spec/install/cooldown_spec.rb

@@ -0,0 +1,158 @@
+# frozen_string_literal: true
+
+RSpec.describe "bundle install with the cooldown setting" do
+  before do
+    build_repo2
+  end
+
+  context "Gemfile DSL" do
+    it "accepts `source ..., cooldown: N` without error" do
+      install_gemfile <<-G, artifice: "compact_index"
+        source "https://gem.repo2", cooldown: 5
+        gem "myrack"
+      G
+
+      expect(the_bundle).to include_gems("myrack 1.0.0")
+    end
+
+    it "accepts `cooldown: 0` to disable cooldown for a source" do
+      install_gemfile <<-G, artifice: "compact_index"
+        source "https://gem.repo2", cooldown: 0
+        gem "myrack"
+      G
+
+      expect(the_bundle).to include_gems("myrack 1.0.0")
+    end
+  end
+
+  context "CLI flag" do
+    before do
+      gemfile <<-G
+        source "https://gem.repo2"
+        gem "myrack"
+      G
+    end
+
+    it "accepts --cooldown N on install" do
+      bundle "install --cooldown 7", artifice: "compact_index"
+
+      expect(the_bundle).to include_gems("myrack 1.0.0")
+    end
+
+    it "accepts --cooldown 0 as an escape hatch" do
+      bundle "install --cooldown 0", artifice: "compact_index"
+
+      expect(the_bundle).to include_gems("myrack 1.0.0")
+    end
+  end
+
+  context "configuration" do
+    it "reads BUNDLE_COOLDOWN as an integer" do
+      gemfile <<-G
+        source "https://gem.repo2"
+        gem "myrack"
+      G
+
+      bundle "install", env: { "BUNDLE_COOLDOWN" => "7" }, artifice: "compact_index"
+
+      expect(the_bundle).to include_gems("myrack 1.0.0")
+    end
+
+    it "reads `bundle config set cooldown N`" do
+      gemfile <<-G
+        source "https://gem.repo2"
+        gem "myrack"
+      G
+
+      bundle "config set cooldown 7"
+      bundle "install", artifice: "compact_index"
+
+      expect(the_bundle).to include_gems("myrack 1.0.0")
+    end
+  end
+
+  context "end-to-end with v2 compact index" do
+    before do
+      now = Time.now.utc
+      build_repo3 do
+        build_gem "ripe_gem", "1.0.0" do |s|
+          s.date = now - (30 * 86_400)
+        end
+        build_gem "ripe_gem", "2.0.0" do |s|
+          s.date = now - (1 * 86_400)
+        end
+      end
+    end
+
+    it "excludes versions within the cooldown window" do
+      gemfile <<-G
+        source "https://gem.repo3"
+        gem "ripe_gem"
+      G
+
+      bundle "install --cooldown 7", artifice: "compact_index_cooldown"
+
+      expect(the_bundle).to include_gems("ripe_gem 1.0.0")
+    end
+
+    it "selects the latest version when --cooldown 0 is passed" do
+      gemfile <<-G
+        source "https://gem.repo3"
+        gem "ripe_gem"
+      G
+
+      bundle "install --cooldown 0", artifice: "compact_index_cooldown"
+
+      expect(the_bundle).to include_gems("ripe_gem 2.0.0")
+    end
+
+    it "applies cooldown declared per-source in the Gemfile" do
+      gemfile <<-G
+        source "https://gem.repo3", cooldown: 7
+        gem "ripe_gem"
+      G
+
+      bundle "install", artifice: "compact_index_cooldown"
+
+      expect(the_bundle).to include_gems("ripe_gem 1.0.0")
+    end
+
+    it "is overridden by CLI --cooldown when Gemfile sets a different per-source value" do
+      gemfile <<-G
+        source "https://gem.repo3", cooldown: 0
+        gem "ripe_gem"
+      G
+
+      bundle "install --cooldown 7", artifice: "compact_index_cooldown"
+
+      expect(the_bundle).to include_gems("ripe_gem 1.0.0")
+    end
+
+    it "bypasses cooldown when bundle install uses an existing lockfile" do
+      gemfile <<-G
+        source "https://gem.repo3"
+        gem "ripe_gem"
+      G
+
+      lockfile <<-L
+        GEM
+          remote: https://gem.repo3/
+          specs:
+            ripe_gem (2.0.0)
+
+        PLATFORMS
+          #{lockfile_platforms}
+
+        DEPENDENCIES
+          ripe_gem
+
+        BUNDLED WITH
+           #{Bundler::VERSION}
+      L
+
+      bundle "install --cooldown 7", artifice: "compact_index_cooldown"
+
+      expect(the_bundle).to include_gems("ripe_gem 2.0.0")
+    end
+  end
+end

spec/support/artifice/compact_index_cooldown.rb

@@ -0,0 +1,6 @@
+# frozen_string_literal: true
+
+require_relative "helpers/compact_index_cooldown"
+require_relative "helpers/artifice"
+
+Artifice.activate_with(CompactIndexCooldownAPI)

spec/support/artifice/helpers/compact_index_cooldown.rb

@@ -0,0 +1,13 @@
+# frozen_string_literal: true
+
+require_relative "compact_index"
+
+class CompactIndexCooldownAPI < CompactIndexAPI
+  helpers do
+    def build_gem_version(spec, deps, checksum)
+      created_at = spec.date&.utc&.iso8601
+      CompactIndex::GemVersionV2.new(spec.version.version, spec.platform.to_s, checksum, nil,
+        deps, spec.required_ruby_version.to_s, spec.required_rubygems_version.to_s, created_at)
+    end
+  end
+end

spec/support/shards.rb

@@ -144,6 +144,7 @@ module Shards
       ],
       shard_d: [
         "spec/bundler/resolver/cooldown_spec.rb",
+        "spec/install/cooldown_spec.rb",
         "spec/commands/outdated_spec.rb",
         "spec/commands/update_spec.rb",
         "spec/lock/lockfile_spec.rb",