From e58c0f2f6508a3a15fd505d97f7991a4265a8019 Mon Sep 17 00:00:00 2001
From: Lukas Oberhuber <lukas.oberhuber@simplybusiness.co.uk>
Date: Mon, 21 Dec 2020 11:30:40 +0000
Subject: [PATCH 1/4] Port of `force_version` POC

Link to POC https://github.com/rubygems/bundler/pull/5670

Co-authored-by: Samuel Giddins <segiddins@segiddins.me>
---
 bundler/lib/bundler/dependency.rb          |  5 ++
 bundler/lib/bundler/dsl.rb                 |  6 ++-
 bundler/lib/bundler/resolver.rb            |  9 +++-
 bundler/lib/bundler/rubygems_ext.rb        |  4 ++
 bundler/spec/install/gemfile/force_spec.rb | 55 ++++++++++++++++++++++
 5 files changed, 77 insertions(+), 2 deletions(-)
 create mode 100644 bundler/spec/install/gemfile/force_spec.rb

diff --git a/bundler/lib/bundler/dependency.rb b/bundler/lib/bundler/dependency.rb
index af07e8bc363c..c35a40e5319d 100644
--- a/bundler/lib/bundler/dependency.rb
+++ b/bundler/lib/bundler/dependency.rb
@@ -89,6 +89,7 @@ def initialize(name, version, options = {}, &blk)
       @gemfile        = options["gemfile"]
 
       @autorequire = Array(options["require"] || []) if options.key?("require")
+      @force_version = options.fetch("force_version", false)
     end
 
     # Returns the platforms this dependency is valid for, in the same order as
@@ -111,6 +112,10 @@ def should_include?
       @should_include && current_env? && current_platform?
     end
 
+    def force_version?
+      @force_version
+    end
+
     def current_env?
       return true unless @env
       if @env.is_a?(Hash)
diff --git a/bundler/lib/bundler/dsl.rb b/bundler/lib/bundler/dsl.rb
index 1cc7908b8a88..9cf23eb278f1 100644
--- a/bundler/lib/bundler/dsl.rb
+++ b/bundler/lib/bundler/dsl.rb
@@ -16,7 +16,7 @@ def self.evaluate(gemfile, lockfile, unlock)
     VALID_PLATFORMS = Bundler::Dependency::PLATFORM_MAP.keys.freeze
 
     VALID_KEYS = %w[group groups git path glob name branch ref tag require submodules
-                    platform platforms type source install_if gemfile].freeze
+                    platform platforms type source install_if gemfile force_version].freeze
 
     attr_reader :gemspecs
     attr_accessor :dependencies
@@ -371,6 +371,10 @@ def normalize_options(name, version, opts)
         opts["source"] = @sources.add_rubygems_source("remotes" => source)
       end
 
+      if opts.key?("force_version") && (r = Gem::Requirement.new(version)) && !r.exact?
+        raise GemfileError, "Cannot use force_version for inexact version requirement `#{r}`"
+      end
+
       git_name = (git_names & opts.keys).last
       if @git_sources[git_name]
         opts["git"] = @git_sources[git_name].call(opts[git_name])
diff --git a/bundler/lib/bundler/resolver.rb b/bundler/lib/bundler/resolver.rb
index 636dc8af4621..adaf960c6d8b 100644
--- a/bundler/lib/bundler/resolver.rb
+++ b/bundler/lib/bundler/resolver.rb
@@ -203,7 +203,7 @@ def name_for_locking_dependency_source
     end
 
     def requirement_satisfied_by?(requirement, activated, spec)
-      requirement.matches_spec?(spec) || spec.source.is_a?(Source::Gemspec)
+      requirement.matches_spec?(spec) || allows_conflicts?(requirement, activated, spec)
     end
 
     def relevant_sources_for_vertex(vertex)
@@ -436,5 +436,12 @@ def validate_resolved_specs!(resolved_specs)
         Bundler.ui.warn "Warning: #{msg}"
       end
     end
+
+    def allows_conflicts?(requirement, activated, spec)
+      return true if spec.source.is_a?(Source::Gemspec)
+      return false if requirement.force_version?
+      return true if activated.vertex_named(spec.name).requirements.any?(&:force_version?)
+      false
+    end
   end
 end
diff --git a/bundler/lib/bundler/rubygems_ext.rb b/bundler/lib/bundler/rubygems_ext.rb
index 0322b06d0787..824b873c3b54 100644
--- a/bundler/lib/bundler/rubygems_ext.rb
+++ b/bundler/lib/bundler/rubygems_ext.rb
@@ -127,6 +127,10 @@ def to_lock
       end
       out
     end
+
+    def force_version?
+      false
+    end
   end
 
   # comparison is done order independently since rubygems 3.2.0.rc.2
diff --git a/bundler/spec/install/gemfile/force_spec.rb b/bundler/spec/install/gemfile/force_spec.rb
new file mode 100644
index 000000000000..9393e5e97088
--- /dev/null
+++ b/bundler/spec/install/gemfile/force_spec.rb
@@ -0,0 +1,55 @@
+# frozen_string_literal: true
+require "spec_helper"
+
+RSpec.describe "bundle install with a gemfile that forces a gem version" do
+  context "with a simple conflict" do
+    it "works" do
+      install_gemfile <<-G
+        source "file:#{gem_repo1}"
+        gem "rack_middleware"
+        gem "rack", "1.0.0", :force_version => true
+      G
+
+      expect(the_bundle).to include_gems("rack 1.0.0", "rack_middleware 1.0")
+    end
+
+    it "raises when forcing to an inexact version" do
+      install_gemfile <<-G
+        gem "rack", "> 1.0.0", :force_version => true
+      G
+
+      bundle :install, :env => { "DEBUG" => "1" }
+
+      expect(out).to include("Cannot use force_version for inexact version requirement `> 1.0.0`.")
+    end
+
+    it "raises when forcing without specifying a version" do
+      install_gemfile <<-G
+        gem "rack", :force_version => true
+      G
+
+      expect(out).to include("Cannot use force_version for inexact version requirement `>= 0`.")
+    end
+
+    it "works when there's no conflict" do
+      install_gemfile <<-G
+        source "file:#{gem_repo1}"
+        gem "rack", "1.0.0", :force_version => true
+      G
+
+      expect(the_bundle).to include_gems("rack 1.0.0")
+    end
+  end
+
+  context "with a complex conflict" do
+    it "works" do
+      install_gemfile <<-G
+        source "file:#{gem_repo1}"
+        gem "rails", "2.3.2"
+        gem "activesupport", "2.3.5", :force_version => true
+      G
+
+      expect(the_bundle).to include_gems("rails 2.3.2", "activesupport 2.3.5", "actionpack 2.3.2", "activerecord 2.3.2", "actionmailer 2.3.2", "activeresource 2.3.2")
+    end
+  end
+end

From 4fb53e85eba565e4ac8c6387728feb9b3b076e29 Mon Sep 17 00:00:00 2001
From: Lukas Oberhuber <lukas.oberhuber@simplybusiness.co.uk>
Date: Mon, 21 Dec 2020 11:31:22 +0000
Subject: [PATCH 2/4] Implement `force_version: true` logic for gems

---
 bundler/lib/bundler.rb                        |   8 +-
 bundler/lib/bundler/resolver.rb               |  30 ++++-
 bundler/lib/bundler/source.rb                 |   4 +
 .../delegates/specification_provider.rb       |   7 +
 .../molinillo/lib/molinillo/resolution.rb     |  12 +-
 bundler/spec/install/gemfile/force_spec.rb    | 122 ++++++++++++++++--
 6 files changed, 164 insertions(+), 19 deletions(-)

diff --git a/bundler/lib/bundler.rb b/bundler/lib/bundler.rb
index c72ad27c401b..cf4ca80eb30a 100644
--- a/bundler/lib/bundler.rb
+++ b/bundler/lib/bundler.rb
@@ -196,6 +196,10 @@ def definition(unlock = nil)
       end
     end
 
+    def definition?
+      defined?(@definition) && @definition
+    end
+
     def frozen_bundle?
       frozen = settings[:deployment]
       frozen ||= settings[:frozen] unless feature_flag.deployment_means_frozen?
@@ -204,7 +208,7 @@ def frozen_bundle?
 
     def locked_gems
       @locked_gems ||=
-        if defined?(@definition) && @definition
+        if definition?
           definition.locked_gems
         elsif Bundler.default_lockfile.file?
           lock = Bundler.read_file(Bundler.default_lockfile)
@@ -213,7 +217,7 @@ def locked_gems
     end
 
     def most_specific_locked_platform?(platform)
-      return false unless defined?(@definition) && @definition
+      return false unless definition?
 
       definition.most_specific_locked_platform == platform
     end
diff --git a/bundler/lib/bundler/resolver.rb b/bundler/lib/bundler/resolver.rb
index adaf960c6d8b..ce8b2c7cf9cf 100644
--- a/bundler/lib/bundler/resolver.rb
+++ b/bundler/lib/bundler/resolver.rb
@@ -203,7 +203,21 @@ def name_for_locking_dependency_source
     end
 
     def requirement_satisfied_by?(requirement, activated, spec)
-      requirement.matches_spec?(spec) || allows_conflicts?(requirement, activated, spec)
+      return true if spec.source.is_a?(Source::Gemspec)
+      return true if requirement.matches_spec?(spec) &&
+        forced_or_no_forced_alternative_spec(requirement, activated, spec)
+      return true if !requirement.matches_spec?(spec) && is_forced_spec(activated, spec)
+      false
+    end
+
+    # Forced version overrides all other requirements
+    def requirements_satisfied_by?(requirements, activated, possibility)
+      forced_req = requirements.find(&:force_version?)
+      if forced_req
+        requirement_satisfied_by?(forced_req, activated, possibility)
+      else
+        requirements.all? {|req| requirement_satisfied_by?(req, activated, possibility) }
+      end
     end
 
     def relevant_sources_for_vertex(vertex)
@@ -225,6 +239,7 @@ def sort_dependencies(dependencies, activated, conflicts)
           @base_dg.vertex_named(name) ? 0 : 1,
           vertex.payload ? 0 : 1,
           vertex.root? ? 0 : 1,
+          dependency.force_version? ? 0 : 1,
           amount_constrained(dependency),
           conflicts[name] ? 0 : 1,
           vertex.payload ? 0 : search_for(dependency).count,
@@ -437,11 +452,14 @@ def validate_resolved_specs!(resolved_specs)
       end
     end
 
-    def allows_conflicts?(requirement, activated, spec)
-      return true if spec.source.is_a?(Source::Gemspec)
-      return false if requirement.force_version?
-      return true if activated.vertex_named(spec.name).requirements.any?(&:force_version?)
-      false
+    def forced_or_no_forced_alternative_spec(requirement, activated, spec)
+      requirement.force_version? || !activated.vertex_named(spec.name)&.requirements&.any?(&:force_version?)
+    end
+
+    def is_forced_spec(activated, spec)
+      activated.vertex_named(spec.name)&.
+        requirements&.select(&:force_version?)&.
+        any? {|r| r.matches_spec?(spec) }
     end
   end
 end
diff --git a/bundler/lib/bundler/source.rb b/bundler/lib/bundler/source.rb
index be00143f5a40..98868c9e53ad 100644
--- a/bundler/lib/bundler/source.rb
+++ b/bundler/lib/bundler/source.rb
@@ -18,6 +18,10 @@ def version_message(spec)
       message = "#{spec.name} #{spec.version}"
       message += " (#{spec.platform})" if spec.platform != Gem::Platform::RUBY && !spec.platform.nil?
 
+      if Bundler.definition? && Bundler.definition.dependencies.select {|d| d.name == spec.name }.any?(&:force_version?)
+        message += " [version forced]"
+      end
+
       if Bundler.locked_gems
         locked_spec = Bundler.locked_gems.specs.find {|s| s.name == spec.name }
         locked_spec_version = locked_spec.version if locked_spec
diff --git a/bundler/lib/bundler/vendor/molinillo/lib/molinillo/delegates/specification_provider.rb b/bundler/lib/bundler/vendor/molinillo/lib/molinillo/delegates/specification_provider.rb
index ec9c770a2889..84b0a940a23e 100644
--- a/bundler/lib/bundler/vendor/molinillo/lib/molinillo/delegates/specification_provider.rb
+++ b/bundler/lib/bundler/vendor/molinillo/lib/molinillo/delegates/specification_provider.rb
@@ -26,6 +26,13 @@ def requirement_satisfied_by?(requirement, activated, spec)
         end
       end
 
+      # (see Bundler::Molinillo::SpecificationProvider#requirements_satisfied_by?)
+      def requirements_satisfied_by?(requirements, activated, spec)
+        with_no_such_dependency_error_handling do
+          specification_provider.requirements_satisfied_by?(requirements, activated, spec)
+        end
+      end
+
       # (see Bundler::Molinillo::SpecificationProvider#name_for)
       def name_for(dependency)
         with_no_such_dependency_error_handling do
diff --git a/bundler/lib/bundler/vendor/molinillo/lib/molinillo/resolution.rb b/bundler/lib/bundler/vendor/molinillo/lib/molinillo/resolution.rb
index 26b8bc745c40..7c22f08750dd 100644
--- a/bundler/lib/bundler/vendor/molinillo/lib/molinillo/resolution.rb
+++ b/bundler/lib/bundler/vendor/molinillo/lib/molinillo/resolution.rb
@@ -218,7 +218,7 @@ def resolve_activated_specs
           next unless vertex.payload
 
           latest_version = vertex.payload.possibilities.reverse_each.find do |possibility|
-            vertex.requirements.all? { |req| requirement_satisfied_by?(req, activated, possibility) }
+            requirements_satisfied_by?(vertex.requirements, activated, possibility)
           end
 
           activated.set_payload(vertex.name, latest_version)
@@ -473,7 +473,7 @@ def possibility_satisfies_requirements?(possibility, requirements)
 
         activated.tag(:swap)
         activated.set_payload(name, possibility) if activated.vertex_named(name)
-        satisfied = requirements.all? { |r| requirement_satisfied_by?(r, activated, possibility) }
+        satisfied = requirements_satisfied_by?(requirements, activated, possibility)
         activated.rewind_to(:swap)
 
         satisfied
@@ -702,7 +702,13 @@ def attempt_to_filter_existing_spec(vertex)
       # @param [Object] vertex existing vertex
       # @return [PossibilitySet] filtered possibility set
       def filtered_possibility_set(vertex)
-        PossibilitySet.new(vertex.payload.dependencies, vertex.payload.possibilities & possibility.possibilities)
+        filtered = if vertex.requirements.any?(&:force_version?)
+          debug(depth) { "Forced version from existing spec (#{vertex.payload})" }
+          vertex.payload.possibilities
+        else
+          vertex.payload.possibilities & possibility.possibilities
+        end
+        PossibilitySet.new(vertex.payload.dependencies, filtered)
       end
 
       # @param [String] requirement_name the spec name to search for
diff --git a/bundler/spec/install/gemfile/force_spec.rb b/bundler/spec/install/gemfile/force_spec.rb
index 9393e5e97088..eb73b2dd96f5 100644
--- a/bundler/spec/install/gemfile/force_spec.rb
+++ b/bundler/spec/install/gemfile/force_spec.rb
@@ -1,11 +1,12 @@
 # frozen_string_literal: true
+
 require "spec_helper"
 
 RSpec.describe "bundle install with a gemfile that forces a gem version" do
   context "with a simple conflict" do
     it "works" do
       install_gemfile <<-G
-        source "file:#{gem_repo1}"
+        source "#{file_uri_for(gem_repo1)}"
         gem "rack_middleware"
         gem "rack", "1.0.0", :force_version => true
       G
@@ -14,42 +15,147 @@
     end
 
     it "raises when forcing to an inexact version" do
-      install_gemfile <<-G
+      gemfile <<-G
         gem "rack", "> 1.0.0", :force_version => true
       G
 
-      bundle :install, :env => { "DEBUG" => "1" }
+      bundle :install, :quiet => true, :raise_on_error => false
 
-      expect(out).to include("Cannot use force_version for inexact version requirement `> 1.0.0`.")
+      expect(exitstatus).to_not eq(0)
+      expect(err).to include("Cannot use force_version for inexact version requirement `> 1.0.0`.")
     end
 
     it "raises when forcing without specifying a version" do
-      install_gemfile <<-G
+      gemfile <<-G
         gem "rack", :force_version => true
       G
 
-      expect(out).to include("Cannot use force_version for inexact version requirement `>= 0`.")
+      bundle :install, :quiet => true, :raise_on_error => false
+
+      expect(exitstatus).to_not eq(0)
+      expect(err).to include("Cannot use force_version for inexact version requirement `>= 0`.")
     end
 
     it "works when there's no conflict" do
       install_gemfile <<-G
-        source "file:#{gem_repo1}"
+        source "#{file_uri_for(gem_repo1)}"
         gem "rack", "1.0.0", :force_version => true
       G
 
       expect(the_bundle).to include_gems("rack 1.0.0")
     end
+
+    it "raises when gem doesn't exist" do
+      gemfile <<-G
+        source "#{file_uri_for(gem_repo1)}"
+        gem "rack_middleware"
+        gem "rack", "2.0.0", :force_version => true
+      G
+
+      bundle :install, :quiet => true, :raise_on_error => false
+
+      expect(exitstatus).to_not eq(0)
+      expect(err).to include("Could not find gem 'rack (= 2.0.0)")
+    end
   end
 
   context "with a complex conflict" do
     it "works" do
       install_gemfile <<-G
-        source "file:#{gem_repo1}"
+        source "#{file_uri_for(gem_repo1)}"
         gem "rails", "2.3.2"
         gem "activesupport", "2.3.5", :force_version => true
       G
 
       expect(the_bundle).to include_gems("rails 2.3.2", "activesupport 2.3.5", "actionpack 2.3.2", "activerecord 2.3.2", "actionmailer 2.3.2", "activeresource 2.3.2")
     end
+
+    it "resolves even with clashing requirements" do
+      build_repo4 do
+        build_gem "first_parent", %w[1.0.0] do |s|
+          s.add_dependency "wasabi", "~> 3.6"
+        end
+        build_gem "second_parent", %w[1.0.0] do |s|
+          s.add_dependency "wasabi", "~> 3.1.0"
+        end
+        build_gem "wasabi", %w[3.1.0 3.6.1]
+      end
+
+      install_gemfile <<-G
+        source "#{file_uri_for(gem_repo4)}"
+        gem "first_parent"
+        gem "second_parent"
+        gem "wasabi", "3.6.1", :force_version => true
+      G
+
+      expect(the_bundle).to include_gems("first_parent 1.0.0", "second_parent 1.0.0", "wasabi 3.6.1")
+    end
+
+    it "resolves even with complex multi-source" do
+      build_repo2 do
+        build_gem "sfmc-fuelsdk-ruby", %w[1.3.2] do |s|
+          s.add_dependency "wasabi", "3.6.1"
+          s.add_dependency "jwt", "~> 2.2"
+        end
+        build_gem "cognito-rack", %w[0.16.6] do |s|
+          s.add_dependency "jwt", "~> 2.2"
+        end
+      end
+
+      build_repo4 do
+        build_gem "skynet", %w[2.0.2] do |s|
+          s.add_dependency "sfmc-fuelsdk-ruby", "1.3.2"
+        end
+        build_gem "sfmc-fuelsdk-ruby", %w[1.3.0] do |s|
+          s.add_dependency "wasabi", "3.1.0"
+          s.add_dependency "jwt", [">= 1.0.0", "~> 1.0"]
+        end
+        build_gem "wasabi", %w[3.1.0 3.6.1]
+        build_gem "jwt", %w[1.0.0 2.2]
+      end
+
+      install_gemfile <<-G
+        source "#{file_uri_for(gem_repo4)}"
+        gem "skynet"
+        source "#{file_uri_for(gem_repo2)}" do
+          gem "sfmc-fuelsdk-ruby"
+          gem "cognito-rack"
+        end
+      G
+
+      gemfile <<-G
+        source "#{file_uri_for(gem_repo4)}"
+        gem "sfmc-fuelsdk-ruby", "1.3.0", :force_version => true
+        gem "jwt", "2.2", :force_version => true
+        gem "skynet"
+        source "#{file_uri_for(gem_repo2)}" do
+          gem "cognito-rack"
+        end
+      G
+
+      bundle "update sfmc-fuelsdk-ruby"
+
+      expect(the_bundle).to include_gems("skynet 2.0.2", "sfmc-fuelsdk-ruby 1.3.0", "wasabi 3.1.0")
+    end
+  end
+
+  context "shows indicator that force_version was active" do
+    it "works" do
+      gemfile <<-G
+        source "#{file_uri_for(gem_repo1)}"
+        gem "rack_middleware"
+        gem "rack", "1.0.0", :force_version => true
+      G
+
+      bundle :install
+
+      expect(out).to include("Installing rack 1.0.0 [version forced]")
+
+      if Gem::Version.create(Bundler::VERSION).segments.first < 3
+        bundle :install
+
+        expect(out).to include("Using rack 1.0.0 [version forced]")
+      end
+    end
   end
 end

From 1d04c7ff95a2dffcb133965717b1b72dc2e3dd24 Mon Sep 17 00:00:00 2001
From: Lukas Oberhuber <lukas.oberhuber@simplybusiness.co.uk>
Date: Sun, 27 Dec 2020 16:11:03 +0000
Subject: [PATCH 3/4] Remove all changes to vendored Molinillo

---
 bundler/lib/bundler/resolver.rb               | 42 +++++++++----------
 .../delegates/specification_provider.rb       |  7 ----
 .../molinillo/lib/molinillo/resolution.rb     | 12 ++----
 3 files changed, 22 insertions(+), 39 deletions(-)

diff --git a/bundler/lib/bundler/resolver.rb b/bundler/lib/bundler/resolver.rb
index ce8b2c7cf9cf..97c98741195e 100644
--- a/bundler/lib/bundler/resolver.rb
+++ b/bundler/lib/bundler/resolver.rb
@@ -46,6 +46,8 @@ def start(requirements)
       @gem_version_promoter.prerelease_specified = @prerelease_specified = {}
       requirements.each {|dep| @prerelease_specified[dep.name] ||= dep.prerelease? }
 
+      @forced_requirements = requirements.select {|dep| dep.force_version? }
+
       verify_gemfile_dependencies_are_found!(requirements)
       dg = @resolver.resolve(requirements, @base_dg)
       dg.
@@ -103,7 +105,14 @@ def indicate_progress
     include Molinillo::SpecificationProvider
 
     def dependencies_for(specification)
-      specification.dependencies_for_activated_platforms
+      deps = specification.dependencies_for_activated_platforms
+      deps.map do |dep|
+        if @forced_requirements.map(&:name).include?(dep.name)
+          @forced_requirements.find {|r| r.name == dep.name }
+        else
+          dep
+        end
+      end
     end
 
     def search_for(dependency_proxy)
@@ -204,23 +213,20 @@ def name_for_locking_dependency_source
 
     def requirement_satisfied_by?(requirement, activated, spec)
       return true if spec.source.is_a?(Source::Gemspec)
-      return true if requirement.matches_spec?(spec) &&
-        forced_or_no_forced_alternative_spec(requirement, activated, spec)
-      return true if !requirement.matches_spec?(spec) && is_forced_spec(activated, spec)
-      false
-    end
 
-    # Forced version overrides all other requirements
-    def requirements_satisfied_by?(requirements, activated, possibility)
-      forced_req = requirements.find(&:force_version?)
-      if forced_req
-        requirement_satisfied_by?(forced_req, activated, possibility)
+      requirements = activated.vertex_named(spec.name)&.requirements
+      if requirements&.any?(&:force_version?)
+        # true if spec matches the forced requirement
+        return true if requirements&.select(&:force_version?)&.
+          any? {|r| r.matches_spec?(spec) }
       else
-        requirements.all? {|req| requirement_satisfied_by?(req, activated, possibility) }
+        return true if requirement.matches_spec?(spec)
       end
+
+      false
     end
 
-    def relevant_sources_for_vertex(vertex)
+   def relevant_sources_for_vertex(vertex)
       if vertex.root?
         [@source_requirements[vertex.name]]
       elsif @lockfile_uses_separate_rubygems_sources
@@ -451,15 +457,5 @@ def validate_resolved_specs!(resolved_specs)
         Bundler.ui.warn "Warning: #{msg}"
       end
     end
-
-    def forced_or_no_forced_alternative_spec(requirement, activated, spec)
-      requirement.force_version? || !activated.vertex_named(spec.name)&.requirements&.any?(&:force_version?)
-    end
-
-    def is_forced_spec(activated, spec)
-      activated.vertex_named(spec.name)&.
-        requirements&.select(&:force_version?)&.
-        any? {|r| r.matches_spec?(spec) }
-    end
   end
 end
diff --git a/bundler/lib/bundler/vendor/molinillo/lib/molinillo/delegates/specification_provider.rb b/bundler/lib/bundler/vendor/molinillo/lib/molinillo/delegates/specification_provider.rb
index 84b0a940a23e..ec9c770a2889 100644
--- a/bundler/lib/bundler/vendor/molinillo/lib/molinillo/delegates/specification_provider.rb
+++ b/bundler/lib/bundler/vendor/molinillo/lib/molinillo/delegates/specification_provider.rb
@@ -26,13 +26,6 @@ def requirement_satisfied_by?(requirement, activated, spec)
         end
       end
 
-      # (see Bundler::Molinillo::SpecificationProvider#requirements_satisfied_by?)
-      def requirements_satisfied_by?(requirements, activated, spec)
-        with_no_such_dependency_error_handling do
-          specification_provider.requirements_satisfied_by?(requirements, activated, spec)
-        end
-      end
-
       # (see Bundler::Molinillo::SpecificationProvider#name_for)
       def name_for(dependency)
         with_no_such_dependency_error_handling do
diff --git a/bundler/lib/bundler/vendor/molinillo/lib/molinillo/resolution.rb b/bundler/lib/bundler/vendor/molinillo/lib/molinillo/resolution.rb
index 7c22f08750dd..26b8bc745c40 100644
--- a/bundler/lib/bundler/vendor/molinillo/lib/molinillo/resolution.rb
+++ b/bundler/lib/bundler/vendor/molinillo/lib/molinillo/resolution.rb
@@ -218,7 +218,7 @@ def resolve_activated_specs
           next unless vertex.payload
 
           latest_version = vertex.payload.possibilities.reverse_each.find do |possibility|
-            requirements_satisfied_by?(vertex.requirements, activated, possibility)
+            vertex.requirements.all? { |req| requirement_satisfied_by?(req, activated, possibility) }
           end
 
           activated.set_payload(vertex.name, latest_version)
@@ -473,7 +473,7 @@ def possibility_satisfies_requirements?(possibility, requirements)
 
         activated.tag(:swap)
         activated.set_payload(name, possibility) if activated.vertex_named(name)
-        satisfied = requirements_satisfied_by?(requirements, activated, possibility)
+        satisfied = requirements.all? { |r| requirement_satisfied_by?(r, activated, possibility) }
         activated.rewind_to(:swap)
 
         satisfied
@@ -702,13 +702,7 @@ def attempt_to_filter_existing_spec(vertex)
       # @param [Object] vertex existing vertex
       # @return [PossibilitySet] filtered possibility set
       def filtered_possibility_set(vertex)
-        filtered = if vertex.requirements.any?(&:force_version?)
-          debug(depth) { "Forced version from existing spec (#{vertex.payload})" }
-          vertex.payload.possibilities
-        else
-          vertex.payload.possibilities & possibility.possibilities
-        end
-        PossibilitySet.new(vertex.payload.dependencies, filtered)
+        PossibilitySet.new(vertex.payload.dependencies, vertex.payload.possibilities & possibility.possibilities)
       end
 
       # @param [String] requirement_name the spec name to search for

From 01e23ef041fe2f9ae731b1b4e68705e7763b7599 Mon Sep 17 00:00:00 2001
From: Lukas Oberhuber <lukas.oberhuber@simplybusiness.co.uk>
Date: Mon, 28 Dec 2020 00:32:34 +0000
Subject: [PATCH 4/4] Simplify code

---
 bundler/lib/bundler/resolver.rb | 28 +++++-----------------------
 1 file changed, 5 insertions(+), 23 deletions(-)

diff --git a/bundler/lib/bundler/resolver.rb b/bundler/lib/bundler/resolver.rb
index 97c98741195e..e463586984bd 100644
--- a/bundler/lib/bundler/resolver.rb
+++ b/bundler/lib/bundler/resolver.rb
@@ -46,7 +46,7 @@ def start(requirements)
       @gem_version_promoter.prerelease_specified = @prerelease_specified = {}
       requirements.each {|dep| @prerelease_specified[dep.name] ||= dep.prerelease? }
 
-      @forced_requirements = requirements.select {|dep| dep.force_version? }
+      @forced_requirements = requirements.select(&:force_version?).map {|dep| [dep.name, dep] }.to_h
 
       verify_gemfile_dependencies_are_found!(requirements)
       dg = @resolver.resolve(requirements, @base_dg)
@@ -106,13 +106,7 @@ def indicate_progress
 
     def dependencies_for(specification)
       deps = specification.dependencies_for_activated_platforms
-      deps.map do |dep|
-        if @forced_requirements.map(&:name).include?(dep.name)
-          @forced_requirements.find {|r| r.name == dep.name }
-        else
-          dep
-        end
-      end
+      deps.map {|dep| @forced_requirements[dep.name] || dep }
     end
 
     def search_for(dependency_proxy)
@@ -212,21 +206,10 @@ def name_for_locking_dependency_source
     end
 
     def requirement_satisfied_by?(requirement, activated, spec)
-      return true if spec.source.is_a?(Source::Gemspec)
-
-      requirements = activated.vertex_named(spec.name)&.requirements
-      if requirements&.any?(&:force_version?)
-        # true if spec matches the forced requirement
-        return true if requirements&.select(&:force_version?)&.
-          any? {|r| r.matches_spec?(spec) }
-      else
-        return true if requirement.matches_spec?(spec)
-      end
-
-      false
+      requirement.matches_spec?(spec) || spec.source.is_a?(Source::Gemspec)
     end
 
-   def relevant_sources_for_vertex(vertex)
+    def relevant_sources_for_vertex(vertex)
       if vertex.root?
         [@source_requirements[vertex.name]]
       elsif @lockfile_uses_separate_rubygems_sources
@@ -238,14 +221,13 @@ def relevant_sources_for_vertex(vertex)
 
     def sort_dependencies(dependencies, activated, conflicts)
       dependencies.sort_by do |dependency|
-        dependency.all_sources = relevant_sources_for_vertex(activated.vertex_named(dependency.name))
         name = name_for(dependency)
+        dependency.all_sources = relevant_sources_for_vertex(activated.vertex_named(name))
         vertex = activated.vertex_named(name)
         [
           @base_dg.vertex_named(name) ? 0 : 1,
           vertex.payload ? 0 : 1,
           vertex.root? ? 0 : 1,
-          dependency.force_version? ? 0 : 1,
           amount_constrained(dependency),
           conflicts[name] ? 0 : 1,
           vertex.payload ? 0 : search_for(dependency).count,