Migrate our resolver engine to PubGrub

  https://github.com/rubygems/rubygems/pull/5960

  Co-authored-by: David Rodríguez <[email protected]>

15 files changed, 181 insertions, 239 deletions

diff --git a/spec/bundler/bundler/definition_spec.rb b/spec/bundler/bundler/definition_spec.rb
index e7235a4e78..372fa2d5e2 100644
--- a/spec/bundler/bundler/definition_spec.rb
+++ b/spec/bundler/bundler/definition_spec.rb
@@ -193,31 +193,6 @@ RSpec.describe Bundler::Definition do
 
   describe "initialize" do
     context "gem version promoter" do
-      context "with lockfile" do
-        before do
-          install_gemfile <<-G
-          source "#{file_uri_for(gem_repo1)}"
-          gem "foo"
-          G
-
-          allow(Bundler::SharedHelpers).to receive(:find_gemfile).and_return(bundled_app_gemfile)
-        end
-
-        it "should get a locked specs list when updating all" do
-          definition = Bundler::Definition.new(bundled_app_lock, [], Bundler::SourceList.new, true)
-          locked_specs = definition.gem_version_promoter.locked_specs
-          expect(locked_specs.to_a.map(&:name)).to eq ["foo"]
-          expect(definition.instance_variable_get("@locked_specs").empty?).to eq true
-        end
-      end
-
-      context "without gemfile or lockfile" do
-        it "should not attempt to parse empty lockfile contents" do
-          definition = Bundler::Definition.new(nil, [], mock_source_list, true)
-          expect(definition.gem_version_promoter.locked_specs.to_a).to eq []
-        end
-      end
-
       context "eager unlock" do
         let(:source_list) do
           Bundler::SourceList.new.tap do |source_list|
diff --git a/spec/bundler/bundler/gem_version_promoter_spec.rb b/spec/bundler/bundler/gem_version_promoter_spec.rb
index 54c559c1d8..b6f10be2aa 100644
--- a/spec/bundler/bundler/gem_version_promoter_spec.rb
+++ b/spec/bundler/bundler/gem_version_promoter_spec.rb
@@ -6,35 +6,32 @@ RSpec.describe Bundler::GemVersionPromoter do
       result.flatten.map(&:version).map(&:to_s)
     end
 
-    def make_instance(*args)
-      @gvp = Bundler::GemVersionPromoter.new(*args).tap do |gvp|
+    def make_instance
+      @gvp = Bundler::GemVersionPromoter.new.tap do |gvp|
         gvp.class.class_eval { public :filter_dep_specs, :sort_dep_specs }
       end
     end
 
-    def unlocking(options)
-      make_instance(Bundler::SpecSet.new([]), ["foo"]).tap do |p|
+    def with_options(options)
+      make_instance.tap do |p|
         p.level = options[:level] if options[:level]
         p.strict = options[:strict] if options[:strict]
       end
     end
 
-    def keep_locked(options)
-      make_instance(Bundler::SpecSet.new([]), ["bar"]).tap do |p|
-        p.level = options[:level] if options[:level]
-        p.strict = options[:strict] if options[:strict]
+    def build_candidates(versions)
+      versions.map do |v|
+        Bundler::Resolver::Candidate.new(v)
       end
     end
 
-    def build_spec_groups(name, versions)
-      versions.map do |v|
-        Bundler::Resolver::SpecGroup.new(build_spec(name, v), [Gem::Platform::RUBY])
-      end
+    def build_spec_set(name, v)
+      Bundler::SpecSet.new(build_spec(name, v))
     end
 
     # Rightmost (highest array index) in result is most preferred.
     # Leftmost (lowest array index) in result is least preferred.
-    # `build_spec_groups` has all versions of gem in index.
+    # `build_candidates` has all versions of gem in index.
     # `build_spec` is the version currently in the .lock file.
     #
     # In default (not strict) mode, all versions in the index will
@@ -43,28 +40,28 @@ RSpec.describe Bundler::GemVersionPromoter do
     # would not consider conservative.
     context "filter specs (strict) level patch" do
       it "when keeping build_spec, keep current, next release" do
-        keep_locked(:level => :patch)
+        with_options(:level => :patch)
         res = @gvp.filter_dep_specs(
-          build_spec_groups("foo", %w[1.7.8 1.7.9 1.8.0]),
-          build_spec("foo", "1.7.8").first
+          build_candidates(%w[1.7.8 1.7.9 1.8.0]),
+          Bundler::Resolver::Package.new("foo", [], build_spec_set("foo", "1.7.8"), [])
         )
-        expect(versions(res)).to eq %w[1.7.9 1.7.8]
+        expect(versions(res)).to match_array %w[1.7.9 1.7.8]
       end
 
       it "when unlocking prefer next release first" do
-        unlocking(:level => :patch)
+        with_options(:level => :patch)
         res = @gvp.filter_dep_specs(
-          build_spec_groups("foo", %w[1.7.8 1.7.9 1.8.0]),
-          build_spec("foo", "1.7.8").first
+          build_candidates(%w[1.7.8 1.7.9 1.8.0]),
+          Bundler::Resolver::Package.new("foo", [], build_spec_set("foo", "1.7.8"), [])
         )
         expect(versions(res)).to eq %w[1.7.8 1.7.9]
       end
 
       it "when unlocking keep current when already at latest release" do
-        unlocking(:level => :patch)
+        with_options(:level => :patch)
         res = @gvp.filter_dep_specs(
-          build_spec_groups("foo", %w[1.7.9 1.8.0 2.0.0]),
-          build_spec("foo", "1.7.9").first
+          build_candidates(%w[1.7.9 1.8.0 2.0.0]),
+          Bundler::Resolver::Package.new("foo", [], build_spec_set("foo", "1.7.9"), [])
         )
         expect(versions(res)).to eq %w[1.7.9]
       end
@@ -72,57 +69,57 @@ RSpec.describe Bundler::GemVersionPromoter do
 
     context "filter specs (strict) level minor" do
       it "when unlocking favor next releases, remove minor and major increases" do
-        unlocking(:level => :minor)
+        with_options(:level => :minor)
         res = @gvp.filter_dep_specs(
-          build_spec_groups("foo", %w[0.2.0 0.3.0 0.3.1 0.9.0 1.0.0 2.0.0 2.0.1]),
-          build_spec("foo", "0.2.0").first
+          build_candidates(%w[0.2.0 0.3.0 0.3.1 0.9.0 1.0.0 2.0.0 2.0.1]),
+          Bundler::Resolver::Package.new("foo", [], build_spec_set("foo", "0.2.0"), [])
         )
         expect(versions(res)).to eq %w[0.2.0 0.3.0 0.3.1 0.9.0]
       end
 
       it "when keep locked, keep current, then favor next release, remove minor and major increases" do
-        keep_locked(:level => :minor)
+        with_options(:level => :minor)
         res = @gvp.filter_dep_specs(
-          build_spec_groups("foo", %w[0.2.0 0.3.0 0.3.1 0.9.0 1.0.0 2.0.0 2.0.1]),
-          build_spec("foo", "0.2.0").first
+          build_candidates(%w[0.2.0 0.3.0 0.3.1 0.9.0 1.0.0 2.0.0 2.0.1]),
+          Bundler::Resolver::Package.new("foo", [], build_spec_set("foo", "0.2.0"), ["bar"])
         )
-        expect(versions(res)).to eq %w[0.3.0 0.3.1 0.9.0 0.2.0]
+        expect(versions(res)).to match_array %w[0.3.0 0.3.1 0.9.0 0.2.0]
       end
     end
 
     context "sort specs (not strict) level patch" do
       it "when not unlocking, same order but make sure build_spec version is most preferred to stay put" do
-        keep_locked(:level => :patch)
+        with_options(:level => :patch)
         res = @gvp.sort_dep_specs(
-          build_spec_groups("foo", %w[1.5.4 1.6.5 1.7.6 1.7.7 1.7.8 1.7.9 1.8.0 1.8.1 2.0.0 2.0.1]),
-          build_spec("foo", "1.7.7").first
+          build_candidates(%w[1.5.4 1.6.5 1.7.6 1.7.7 1.7.8 1.7.9 1.8.0 1.8.1 2.0.0 2.0.1]),
+          Bundler::Resolver::Package.new("foo", [], build_spec_set("foo", "1.7.7"), ["bar"])
         )
         expect(versions(res)).to eq %w[1.5.4 1.6.5 1.7.6 2.0.0 2.0.1 1.8.0 1.8.1 1.7.8 1.7.9 1.7.7]
       end
 
       it "when unlocking favor next release, then current over minor increase" do
-        unlocking(:level => :patch)
+        with_options(:level => :patch)
         res = @gvp.sort_dep_specs(
-          build_spec_groups("foo", %w[1.7.7 1.7.8 1.7.9 1.8.0]),
-          build_spec("foo", "1.7.8").first
+          build_candidates(%w[1.7.7 1.7.8 1.7.9 1.8.0]),
+          Bundler::Resolver::Package.new("foo", [], build_spec_set("foo", "1.7.8"), [])
         )
         expect(versions(res)).to eq %w[1.7.7 1.8.0 1.7.8 1.7.9]
       end
 
       it "when unlocking do proper integer comparison, not string" do
-        unlocking(:level => :patch)
+        with_options(:level => :patch)
         res = @gvp.sort_dep_specs(
-          build_spec_groups("foo", %w[1.7.7 1.7.8 1.7.9 1.7.15 1.8.0]),
-          build_spec("foo", "1.7.8").first
+          build_candidates(%w[1.7.7 1.7.8 1.7.9 1.7.15 1.8.0]),
+          Bundler::Resolver::Package.new("foo", [], build_spec_set("foo", "1.7.8"), [])
         )
         expect(versions(res)).to eq %w[1.7.7 1.8.0 1.7.8 1.7.9 1.7.15]
       end
 
       it "leave current when unlocking but already at latest release" do
-        unlocking(:level => :patch)
+        with_options(:level => :patch)
         res = @gvp.sort_dep_specs(
-          build_spec_groups("foo", %w[1.7.9 1.8.0 2.0.0]),
-          build_spec("foo", "1.7.9").first
+          build_candidates(%w[1.7.9 1.8.0 2.0.0]),
+          Bundler::Resolver::Package.new("foo", [], build_spec_set("foo", "1.7.9"), [])
         )
         expect(versions(res)).to eq %w[2.0.0 1.8.0 1.7.9]
       end
@@ -130,10 +127,10 @@ RSpec.describe Bundler::GemVersionPromoter do
 
     context "sort specs (not strict) level minor" do
       it "when unlocking favor next release, then minor increase over current" do
-        unlocking(:level => :minor)
+        with_options(:level => :minor)
         res = @gvp.sort_dep_specs(
-          build_spec_groups("foo", %w[0.2.0 0.3.0 0.3.1 0.9.0 1.0.0 2.0.0 2.0.1]),
-          build_spec("foo", "0.2.0").first
+          build_candidates(%w[0.2.0 0.3.0 0.3.1 0.9.0 1.0.0 2.0.0 2.0.1]),
+          Bundler::Resolver::Package.new("foo", [], build_spec_set("foo", "0.2.0"), [])
         )
         expect(versions(res)).to eq %w[2.0.0 2.0.1 1.0.0 0.2.0 0.3.0 0.3.1 0.9.0]
       end
diff --git a/spec/bundler/bundler/resolver/candidate_spec.rb b/spec/bundler/bundler/resolver/candidate_spec.rb
new file mode 100644
index 0000000000..0840f77245
--- /dev/null
+++ b/spec/bundler/bundler/resolver/candidate_spec.rb
@@ -0,0 +1,10 @@
+# frozen_string_literal: true
+
+RSpec.describe Bundler::Resolver::Candidate do
+  it "compares fine" do
+    version1 = described_class.new("1.12.5", :specs => [Gem::Specification.new("foo", "1.12.5") {|s| s.platform = Gem::Platform::RUBY }])
+    version2 = described_class.new("1.12.5")
+
+    expect(version1 >= version2).to be true
+  end
+end
diff --git a/spec/bundler/bundler/version_ranges_spec.rb b/spec/bundler/bundler/version_ranges_spec.rb
deleted file mode 100644
index bca044b0c0..0000000000
--- a/spec/bundler/bundler/version_ranges_spec.rb
+++ /dev/null
@@ -1,40 +0,0 @@
-# frozen_string_literal: true
-
-require "bundler/version_ranges"
-
-RSpec.describe Bundler::VersionRanges do
-  describe ".empty?" do
-    shared_examples_for "empty?" do |exp, *req|
-      it "returns #{exp} for #{req}" do
-        r = Gem::Requirement.new(*req)
-        ranges = described_class.for(r)
-        expect(described_class.empty?(*ranges)).to eq(exp), "expected `#{r}` #{exp ? "" : "not "}to be empty"
-      end
-    end
-
-    include_examples "empty?", false
-    include_examples "empty?", false, "!= 1"
-    include_examples "empty?", false, "!= 1", "= 2"
-    include_examples "empty?", false, "!= 1", "> 1"
-    include_examples "empty?", false, "!= 1", ">= 1"
-    include_examples "empty?", false, "= 1", ">= 0.1", "<= 1.1"
-    include_examples "empty?", false, "= 1", ">= 1", "<= 1"
-    include_examples "empty?", false, "= 1", "~> 1"
-    include_examples "empty?", false, ">= 0.z", "= 0"
-    include_examples "empty?", false, ">= 0"
-    include_examples "empty?", false, ">= 1.0.0", "< 2.0.0"
-    include_examples "empty?", false, "~> 1"
-    include_examples "empty?", false, "~> 2.0", "~> 2.1"
-    include_examples "empty?", true, ">= 4.1.0", "< 5.0", "= 5.2.1"
-    include_examples "empty?", true, "< 5.0", "< 5.3", "< 6.0", "< 6", "= 5.2.0", "> 2", ">= 3.0", ">= 3.1", ">= 3.2", ">= 4.0.0", ">= 4.1.0", ">= 4.2.0", ">= 4.2", ">= 4"
-    include_examples "empty?", true, "!= 1", "< 2", "> 2"
-    include_examples "empty?", true, "!= 1", "<= 1", ">= 1"
-    include_examples "empty?", true, "< 2", "> 2"
-    include_examples "empty?", true, "< 2", "> 2", "= 2"
-    include_examples "empty?", true, "= 1", "!= 1"
-    include_examples "empty?", true, "= 1", "= 2"
-    include_examples "empty?", true, "= 1", "~> 2"
-    include_examples "empty?", true, ">= 0", "<= 0.a"
-    include_examples "empty?", true, "~> 2.0", "~> 3"
-  end
-end
diff --git a/spec/bundler/install/bundler_spec.rb b/spec/bundler/install/bundler_spec.rb
index 963ce82db8..ae7c94c31f 100644
--- a/spec/bundler/install/bundler_spec.rb
+++ b/spec/bundler/install/bundler_spec.rb
@@ -37,12 +37,11 @@ RSpec.describe "bundle install" do
       G
 
       nice_error = <<-E.strip.gsub(/^ {8}/, "")
-        Bundler could not find compatible versions for gem "bundler":
-          In Gemfile:
-            bundler (= 0.9.1)
+        Could not find compatible versions
 
-          Current Bundler version:
-            bundler (#{Bundler::VERSION})
+        Because the current Bundler version (#{Bundler::VERSION}) does not satisfy bundler = 0.9.1
+          and Gemfile depends on bundler = 0.9.1,
+          version solving has failed.
 
         Your bundle requires a different version of Bundler than the one you're running.
         Install the necessary version with `gem install bundler:0.9.1` and rerun bundler using `bundle _0.9.1_ install`
@@ -58,12 +57,14 @@ RSpec.describe "bundle install" do
       G
 
       nice_error = <<-E.strip.gsub(/^ {8}/, "")
-        Bundler could not find compatible versions for gem "bundler":
-          In Gemfile:
-            bundler (~> 0.8)
+        Could not find compatible versions
 
-          Current Bundler version:
-            bundler (#{Bundler::VERSION})
+        Because rails >= 3.0 depends on bundler >= 0.9.0.pre
+          and the current Bundler version (#{Bundler::VERSION}) does not satisfy bundler >= 0.9.0.pre, < 1.A,
+          rails >= 3.0 requires bundler >= 1.A.
+        So, because Gemfile depends on rails = 3.0
+          and Gemfile depends on bundler ~> 0.8,
+          version solving has failed.
 
         Your bundle requires a different version of Bundler than the one you're running.
         Install the necessary version with `gem install bundler:0.9.1` and rerun bundler using `bundle _0.9.1_ install`
@@ -79,12 +80,11 @@ RSpec.describe "bundle install" do
       G
 
       nice_error = <<-E.strip.gsub(/^ {8}/, "")
-        Bundler could not find compatible versions for gem "bundler":
-          In Gemfile:
-            bundler (= 0.9.2)
+        Could not find compatible versions
 
-          Current Bundler version:
-            bundler (#{Bundler::VERSION})
+        Because the current Bundler version (#{Bundler::VERSION}) does not satisfy bundler = 0.9.2
+          and Gemfile depends on bundler = 0.9.2,
+          version solving has failed.
 
         Your bundle requires a different version of Bundler than the one you're running, and that version could not be found.
         E
@@ -150,13 +150,14 @@ RSpec.describe "bundle install" do
       G
 
       nice_error = <<-E.strip.gsub(/^ {8}/, "")
-        Bundler could not find compatible versions for gem "activesupport":
-          In Gemfile:
-            activemerchant was resolved to 1.0, which depends on
-              activesupport (>= 2.0.0)
-
-            rails_pinned_to_old_activesupport was resolved to 1.0, which depends on
-              activesupport (= 1.2.3)
+        Could not find compatible versions
+
+        Because every version of rails_pinned_to_old_activesupport depends on activesupport = 1.2.3
+          and every version of activemerchant depends on activesupport >= 2.0.0,
+          every version of rails_pinned_to_old_activesupport is incompatible with activemerchant >= 0.
+        So, because Gemfile depends on activemerchant >= 0
+          and Gemfile depends on rails_pinned_to_old_activesupport >= 0,
+          version solving has failed.
       E
       expect(err).to include(nice_error)
     end
@@ -177,12 +178,13 @@ RSpec.describe "bundle install" do
       G
 
       nice_error = <<-E.strip.gsub(/^ {8}/, "")
-        Bundler could not find compatible versions for gem "activesupport":
-          In Gemfile:
-            activesupport (= 2.3.5)
+        Could not find compatible versions
 
-            rails_pinned_to_old_activesupport was resolved to 1.0, which depends on
-              activesupport (= 1.2.3)
+        Because every version of rails_pinned_to_old_activesupport depends on activesupport = 1.2.3
+          and Gemfile depends on rails_pinned_to_old_activesupport >= 0,
+          activesupport = 1.2.3 is required.
+        So, because Gemfile depends on activesupport = 2.3.5,
+          version solving has failed.
       E
       expect(err).to include(nice_error)
     end
diff --git a/spec/bundler/install/gemfile/git_spec.rb b/spec/bundler/install/gemfile/git_spec.rb
index fb99c99b2d..636a3daaad 100644
--- a/spec/bundler/install/gemfile/git_spec.rb
+++ b/spec/bundler/install/gemfile/git_spec.rb
@@ -881,7 +881,7 @@ RSpec.describe "bundle install with git sources" do
         gem "has_submodule"
       end
     G
-    expect(err).to match(/could not find gem 'submodule/i)
+    expect(err).to match(%r{submodule >= 0 could not be found in rubygems repository #{file_uri_for(gem_repo1)}/ or installed locally})
 
     expect(the_bundle).not_to include_gems "has_submodule 1.0"
   end
diff --git a/spec/bundler/install/gemfile/sources_spec.rb b/spec/bundler/install/gemfile/sources_spec.rb
index d2733993bb..174bac511e 100644
--- a/spec/bundler/install/gemfile/sources_spec.rb
+++ b/spec/bundler/install/gemfile/sources_spec.rb
@@ -371,7 +371,15 @@ RSpec.describe "bundle install with gems on multiple sources" do
 
       it "fails" do
         bundle :install, :artifice => "compact_index", :raise_on_error => false
-        expect(err).to include("Could not find gem 'missing', which is required by gem 'depends_on_missing', in any of the sources.")
+        expect(err).to end_with <<~E.strip
+          Could not find compatible versions
+
+          Because every version of depends_on_missing depends on missing >= 0
+            and missing >= 0 could not be found in any of the sources,
+            every version of depends_on_missing is forbidden.
+          So, because Gemfile depends on depends_on_missing >= 0,
+            version solving has failed.
+        E
       end
     end
 
@@ -425,9 +433,15 @@ RSpec.describe "bundle install with gems on multiple sources" do
 
         it "does not find the dependency" do
           bundle :install, :artifice => "compact_index", :raise_on_error => false
-          expect(err).to include(
-            "Could not find gem 'rack', which is required by gem 'depends_on_rack', in rubygems repository https://gem.repo2/ or installed locally."
-          )
+          expect(err).to end_with <<~E.strip
+            Could not find compatible versions
+
+            Because every version of depends_on_rack depends on rack >= 0
+              and rack >= 0 could not be found in rubygems repository https://gem.repo2/ or installed locally,
+              every version of depends_on_rack is forbidden.
+            So, because Gemfile depends on depends_on_rack >= 0,
+              version solving has failed.
+          E
         end
       end
 
diff --git a/spec/bundler/install/gemfile/specific_platform_spec.rb b/spec/bundler/install/gemfile/specific_platform_spec.rb
index 98efec396c..1f615ec8a5 100644
--- a/spec/bundler/install/gemfile/specific_platform_spec.rb
+++ b/spec/bundler/install/gemfile/specific_platform_spec.rb
@@ -370,6 +370,16 @@ RSpec.describe "bundle install with specific platforms" do
         * sorbet-static-0.5.6433-x86_64-linux
     ERROR
 
+    error_message = <<~ERROR.strip
+      Could not find compatible versions
+
+      Because every version of sorbet depends on sorbet-static = 0.5.6433
+        and sorbet-static = 0.5.6433 could not be found in rubygems repository #{file_uri_for(gem_repo4)}/ or installed locally,
+        every version of sorbet is forbidden.
+      So, because Gemfile depends on sorbet = 0.5.6433,
+        version solving has failed.
+    ERROR
+
     simulate_platform "arm64-darwin-21" do
       bundle "lock", :raise_on_error => false
     end
diff --git a/spec/bundler/install/gems/flex_spec.rb b/spec/bundler/install/gems/flex_spec.rb
index ed30d2cc35..4bbb2ea038 100644
--- a/spec/bundler/install/gems/flex_spec.rb
+++ b/spec/bundler/install/gems/flex_spec.rb
@@ -194,11 +194,13 @@ RSpec.describe "bundle flex_install" do
       bundle "config set force_ruby_platform true"
 
       nice_error = <<-E.strip.gsub(/^ {8}/, "")
-        Could not find gem 'rack (= 1.2)', which is required by gem 'rack-obama (= 2.0)', in rubygems repository #{file_uri_for(gem_repo2)}/ or installed locally.
+        Could not find compatible versions
 
-        The source contains the following gems matching 'rack':
-          * rack-0.9.1
-          * rack-1.0.0
+        Because rack-obama >= 2.0 depends on rack = 1.2
+          and rack = 1.2 could not be found in rubygems repository #{file_uri_for(gem_repo2)}/ or installed locally,
+          rack-obama >= 2.0 is forbidden.
+        So, because Gemfile depends on rack-obama = 2.0,
+          version solving has failed.
       E
 
       bundle :install, :retry => 0, :raise_on_error => false
diff --git a/spec/bundler/install/gems/resolving_spec.rb b/spec/bundler/install/gems/resolving_spec.rb
index 7a5307720f..3977122568 100644
--- a/spec/bundler/install/gems/resolving_spec.rb
+++ b/spec/bundler/install/gems/resolving_spec.rb
@@ -159,7 +159,7 @@ RSpec.describe "bundle install with install-time dependencies" do
 
         bundle :install, :env => { "BUNDLER_DEBUG_RESOLVER" => "1", "DEBUG" => "1" }
 
-        expect(out).to include("BUNDLER: Starting resolution")
+        expect(out).to include("Resolving dependencies...")
       end
     end
 
@@ -173,7 +173,7 @@ RSpec.describe "bundle install with install-time dependencies" do
 
         bundle :install, :env => { "DEBUG_RESOLVER" => "1", "DEBUG" => "1" }
 
-        expect(out).to include("BUNDLER: Starting resolution")
+        expect(out).to include("Resolving dependencies...")
       end
     end
 
@@ -187,12 +187,10 @@ RSpec.describe "bundle install with install-time dependencies" do
 
         bundle :install, :env => { "DEBUG_RESOLVER_TREE" => "1", "DEBUG" => "1" }
 
-        activated_groups = "net_b (1.0) (ruby)"
-
         expect(out).to include(" net_b").
-          and include("BUNDLER: Starting resolution").
-          and include("BUNDLER: Finished resolution").
-          and include("Attempting to activate [#{activated_groups}]")
+          and include("Resolving dependencies...").
+          and include("Solution found after 1 attempts:").
+          and include("selecting net_b 1.0")
       end
     end
   end
@@ -379,12 +377,12 @@ RSpec.describe "bundle install with install-time dependencies" do
       it "gives a meaningful error on ruby version mismatches between dependencies" do
         build_repo4 do
           build_gem "requires-old-ruby" do |s|
-            s.required_ruby_version = "< #{RUBY_VERSION}"
+            s.required_ruby_version = "< #{Gem.ruby_version}"
           end
         end
 
         build_lib("foo", :path => bundled_app) do |s|
-          s.required_ruby_version = ">= #{RUBY_VERSION}"
+          s.required_ruby_version = ">= #{Gem.ruby_version}"
 
           s.add_dependency "requires-old-ruby"
         end
@@ -394,7 +392,16 @@ RSpec.describe "bundle install with install-time dependencies" do
           gemspec
         G
 
-        expect(err).to include("Bundler found conflicting requirements for the Ruby\0 version:")
+        expect(err).to end_with <<~E.strip
+          Could not find compatible versions
+
+          Because every version of foo depends on requires-old-ruby >= 0
+            and every version of requires-old-ruby depends on Ruby < #{Gem.ruby_version},
+            every version of foo requires Ruby < #{Gem.ruby_version}.
+          So, because Gemfile depends on foo >= 0
+            and current Ruby version is = #{Gem.ruby_version},
+            version solving has failed.
+        E
       end
 
       it "installs the older version under rate limiting conditions" do
@@ -464,14 +471,13 @@ RSpec.describe "bundle install with install-time dependencies" do
         expect(out).to_not include("Gem::InstallError: require_ruby requires Ruby version > 9000")
 
         nice_error = strip_whitespace(<<-E).strip
-          Bundler found conflicting requirements for the Ruby\0 version:
-            In Gemfile:
-              require_ruby was resolved to 1.0, which depends on
-                Ruby\0 (> 9000)
-
-            Current Ruby\0 version:
-              Ruby\0 (#{error_message_requirement})
+          Could not find compatible versions
 
+          Because every version of require_ruby depends on Ruby > 9000
+            and Gemfile depends on require_ruby >= 0,
+            Ruby > 9000 is required.
+          So, because current Ruby version is #{error_message_requirement},
+            version solving has failed.
         E
         expect(err).to end_with(nice_error)
       end
@@ -487,14 +493,13 @@ RSpec.describe "bundle install with install-time dependencies" do
           expect(out).to_not include("Gem::InstallError: require_ruby requires Ruby version > 9000")
 
           nice_error = strip_whitespace(<<-E).strip
-            Bundler found conflicting requirements for the Ruby\0 version:
-              In Gemfile:
-                require_ruby was resolved to 1.0, which depends on
-                  Ruby\0 (> 9000)
-
-              Current Ruby\0 version:
-                Ruby\0 (#{error_message_requirement})
+            Could not find compatible versions
 
+            Because every version of require_ruby depends on Ruby > 9000
+              and Gemfile depends on require_ruby >= 0,
+              Ruby > 9000 is required.
+            So, because current Ruby version is #{error_message_requirement},
+              version solving has failed.
           E
           expect(err).to end_with(nice_error)
         end
@@ -532,14 +537,11 @@ RSpec.describe "bundle install with install-time dependencies" do
 
       expect(err).to_not include("Gem::InstallError: require_rubygems requires RubyGems version > 9000")
       nice_error = strip_whitespace(<<-E).strip
-        Bundler found conflicting requirements for the RubyGems\0 version:
-          In Gemfile:
-            require_rubygems was resolved to 1.0, which depends on
-              RubyGems\0 (> 9000)
-
-          Current RubyGems\0 version:
-            RubyGems\0 (= #{Gem::VERSION})
-
+        Because every version of require_rubygems depends on RubyGems > 9000
+          and Gemfile depends on require_rubygems >= 0,
+          RubyGems > 9000 is required.
+        So, because current RubyGems version is = #{Gem::VERSION},
+          version solving has failed.
       E
       expect(err).to end_with(nice_error)
     end
diff --git a/spec/bundler/realworld/edgecases_spec.rb b/spec/bundler/realworld/edgecases_spec.rb
index a98859c2d9..e1bb92d36e 100644
--- a/spec/bundler/realworld/edgecases_spec.rb
+++ b/spec/bundler/realworld/edgecases_spec.rb
@@ -11,7 +11,8 @@ RSpec.describe "real world edgecases", :realworld => true do
         source = Bundler::Source::Rubygems::Remote.new(Bundler::URI("https://rubygems.org"))
         fetcher = Bundler::Fetcher.new(source)
         index = fetcher.specs([#{name.dump}], nil)
-        index.search(Gem::Dependency.new(#{name.dump}, #{requirement.dump})).last
+        requirement = Gem::Requirement.create(#{requirement.dump})
+        index.search(#{name.dump}).select {|spec| requirement.satisfied_by?(spec.version) }.last
       end
       if rubygem.nil?
         raise "Could not find #{name} (#{requirement}) on rubygems.org!\n" \
diff --git a/spec/bundler/resolver/basic_spec.rb b/spec/bundler/resolver/basic_spec.rb
index b583fb8715..41c6d9972c 100644
--- a/spec/bundler/resolver/basic_spec.rb
+++ b/spec/bundler/resolver/basic_spec.rb
@@ -104,7 +104,7 @@ RSpec.describe "Resolving" do
     dep "chef_app_error"
     expect do
       resolve
-    end.to raise_error(Bundler::VersionConflict)
+    end.to raise_error(Bundler::SolveFailure)
   end
 
   it "raises an exception with the minimal set of conflicting dependencies" do
@@ -118,14 +118,15 @@ RSpec.describe "Resolving" do
     dep "c"
     expect do
       resolve
-    end.to raise_error(Bundler::VersionConflict, <<-E.strip)
-Bundler could not find compatible versions for gem "a":
-  In Gemfile:
-    b was resolved to 1.0, which depends on
-      a (>= 2)
-
-    c was resolved to 1.0, which depends on
-      a (< 1)
+    end.to raise_error(Bundler::SolveFailure, <<~E.strip)
+      Could not find compatible versions
+
+      Because every version of c depends on a < 1
+        and every version of b depends on a >= 2,
+        every version of c is incompatible with b >= 0.
+      So, because Gemfile depends on b >= 0
+        and Gemfile depends on c >= 0,
+        version solving has failed.
     E
   end
 
@@ -134,7 +135,7 @@ Bundler could not find compatible versions for gem "a":
     dep "circular_app"
 
     expect do
-      resolve
+      Bundler::SpecSet.new(resolve).sort
     end.to raise_error(Bundler::CyclicDependencyError, /please remove either gem 'bar' or gem 'foo'/i)
   end
 
diff --git a/spec/bundler/resolver/platform_spec.rb b/spec/bundler/resolver/platform_spec.rb
index 418293365c..2d143fd84a 100644
--- a/spec/bundler/resolver/platform_spec.rb
+++ b/spec/bundler/resolver/platform_spec.rb
@@ -210,39 +210,6 @@ RSpec.describe "Resolving platform craziness" do
     should_resolve_as %w[foo-1.1.0]
   end
 
-  it "doesn't include gems not needed for none of the platforms" do
-    @index = build_index do
-      gem "empyrean", "0.1.0"
-      gem "coderay", "1.1.2"
-      gem "method_source", "0.9.0"
-
-      gem "spoon", "0.0.6" do
-        dep "ffi", ">= 0"
-      end
-
-      gem "pry", "0.11.3", "java" do
-        dep "coderay", "~> 1.1.0"
-        dep "method_source", "~> 0.9.0"
-        dep "spoon", "~> 0.0"
-      end
-
-      gem "pry", "0.11.3" do
-        dep "coderay", "~> 1.1.0"
-        dep "method_source", "~> 0.9.0"
-      end
-
-      gem "ffi", "1.9.23", "java"
-      gem "ffi", "1.9.23"
-    end
-
-    dep "empyrean", "0.1.0"
-    dep "pry"
-
-    platforms "ruby", "java"
-
-    should_resolve_as %w[coderay-1.1.2 empyrean-0.1.0 ffi-1.9.23-java method_source-0.9.0 pry-0.11.3 pry-0.11.3-java spoon-0.0.6]
-  end
-
   it "includes gems needed for at least one platform" do
     @index = build_index do
       gem "empyrean", "0.1.0"
diff --git a/spec/bundler/runtime/inline_spec.rb b/spec/bundler/runtime/inline_spec.rb
index d53e8663a6..fd1dd6dc26 100644
--- a/spec/bundler/runtime/inline_spec.rb
+++ b/spec/bundler/runtime/inline_spec.rb
@@ -96,12 +96,14 @@ RSpec.describe "bundler/inline#gemfile" do
   it "lets me use my own ui object" do
     script <<-RUBY, :artifice => "endpoint"
       require '#{entrypoint}'
-      class MyBundlerUI < Bundler::UI::Silent
+      class MyBundlerUI < Bundler::UI::Shell
         def confirm(msg, newline = nil)
           puts "CONFIRMED!"
         end
       end
-      gemfile(true, :ui => MyBundlerUI.new) do
+      my_ui = MyBundlerUI.new
+      my_ui.level = "confirm"
+      gemfile(true, :ui => my_ui) do
         source "https://notaserver.com"
         gem "activesupport", :require => true
       end
diff --git a/spec/bundler/support/indexes.rb b/spec/bundler/support/indexes.rb
index e20059429c..744dd6e233 100644
--- a/spec/bundler/support/indexes.rb
+++ b/spec/bundler/support/indexes.rb
@@ -18,15 +18,22 @@ module Spec
       @platforms ||= ["ruby"]
       default_source = instance_double("Bundler::Source::Rubygems", :specs => @index, :to_s => "locally install gems")
       source_requirements = { :default => default_source }
-      @deps.each do |d|
-        source_requirements[d.name] = d.source = default_source
-      end
       args[0] ||= Bundler::SpecSet.new([]) # base
       args[0].each {|ls| ls.source = default_source }
       args[1] ||= Bundler::GemVersionPromoter.new # gem_version_promoter
       args[2] ||= [] # additional_base_requirements
-      args[3] ||= @platforms # platforms
-      Bundler::Resolver.new(source_requirements, *args).start(@deps)
+      originally_locked = args[3] || Bundler::SpecSet.new([])
+      unlock = args[4] || []
+      packages = Hash.new do |h, k|
+        h[k] = Bundler::Resolver::Package.new(k, @platforms, originally_locked, unlock)
+      end
+      @deps.each do |d|
+        name = d.name
+        platforms = d.gem_platforms(@platforms)
+        source_requirements[name] = d.source = default_source
+        packages[name] = Bundler::Resolver::Package.new(name, platforms, originally_locked, unlock, :dependency => d)
+      end
+      Bundler::Resolver.new(source_requirements, *args[0..2]).start(@deps, packages)
     end
 
     def should_not_resolve
@@ -47,13 +54,6 @@ module Spec
       end
     end
 
-    def should_conflict_on(names)
-      got = resolve
-      raise "The resolve succeeded with: #{got.map(&:full_name).sort.inspect}"
-    rescue Bundler::VersionConflict => e
-      expect(Array(names).sort).to eq(e.conflicts.sort)
-    end
-
     def gem(*args, &blk)
       build_spec(*args, &blk).first
     end
@@ -67,12 +67,11 @@ module Spec
     def should_conservative_resolve_and_include(opts, unlock, specs)
       # empty unlock means unlock all
       opts = Array(opts)
-      search = Bundler::GemVersionPromoter.new(@locked, unlock).tap do |s|
+      search = Bundler::GemVersionPromoter.new.tap do |s|
         s.level = opts.first
         s.strict = opts.include?(:strict)
-        s.prerelease_specified = Hash[@deps.map {|d| [d.name, d.requirement.prerelease?] }]
       end
-      should_resolve_and_include specs, [@base, search]
+      should_resolve_and_include specs, [@base, search, [], @locked, unlock]
     end
 
     def an_awesome_index