Migrate our resolver engine to PubGrub

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

  Co-authored-by: David Rodríguez <deivid.rodriguez@riseup.net>

1 files changed, 234 insertions, 258 deletions

diff --git a/lib/bundler/resolver.rb b/lib/bundler/resolver.rb
index 115c5cfcc4..07607813ec 100644
--- a/lib/bundler/resolver.rb
+++ b/lib/bundler/resolver.rb
@@ -1,81 +1,128 @@
 # frozen_string_literal: true
 
 module Bundler
+  #
+  # This class implements the interface needed by PubGrub for resolution. It is
+  # equivalent to the `PubGrub::BasicPackageSource` class provided by PubGrub by
+  # default and used by the most simple PubGrub consumers.
+  #
   class Resolver
-    require_relative "vendored_molinillo"
+    require_relative "vendored_pub_grub"
     require_relative "resolver/base"
-    require_relative "resolver/spec_group"
+    require_relative "resolver/package"
+    require_relative "resolver/candidate"
+    require_relative "resolver/root"
 
     include GemHelpers
 
-    def initialize(source_requirements, base, gem_version_promoter, additional_base_requirements, platforms)
+    def initialize(source_requirements, base, gem_version_promoter, additional_base_requirements)
       @source_requirements = source_requirements
       @base = Resolver::Base.new(base, additional_base_requirements)
-      @resolver = Molinillo::Resolver.new(self, self)
-      @results_for = {}
-      @search_for = {}
-      @platforms = platforms
-      @resolving_only_for_ruby = platforms == [Gem::Platform::RUBY]
       @gem_version_promoter = gem_version_promoter
     end
 
-    def start(requirements, exclude_specs: [])
-      @metadata_requirements, regular_requirements = requirements.partition {|dep| dep.name.end_with?("\0") }
-
+    def start(requirements, packages, exclude_specs: [])
       exclude_specs.each do |spec|
         remove_from_candidates(spec)
       end
 
-      requirements.each {|dep| prerelease_specified[dep.name] ||= dep.prerelease? }
+      root = Resolver::Root.new(name_for_explicit_dependency_source)
+      root_version = Resolver::Candidate.new(0)
+
+      @sorted_versions = Hash.new do |candidates, package|
+        candidates[package] = if package.root?
+          [root_version]
+        else
+          all_versions_for(package).sort
+        end
+      end
+
+      root_dependencies = prepare_dependencies(requirements, packages)
+
+      @cached_dependencies = Hash.new do |dependencies, package|
+        dependencies[package] = if package.root?
+          { root_version => root_dependencies }
+        else
+          Hash.new do |versions, version|
+            versions[version] = to_dependency_hash(version.dependencies, packages)
+          end
+        end
+      end
+
+      logger = Bundler::UI::Shell.new
+      logger.level = debug? ? "debug" : "warn"
+      solver = PubGrub::VersionSolver.new(:source => self, :root => root, :logger => logger)
+      before_resolution
+      result = solver.solve
+      after_resolution
+      result.map {|package, version| version.to_specs(package) }.flatten.uniq
+    rescue PubGrub::SolveFailure => e
+      incompatibility = e.incompatibility
+
+      names_to_unlock = []
+      conflict_on_bundler = nil
+
+      while incompatibility.conflict?
+        cause = incompatibility.cause
+        incompatibility = cause.incompatibility
 
-      verify_gemfile_dependencies_are_found!(requirements)
-      result = @resolver.resolve(requirements).
-        map(&:payload).
-        reject {|sg| sg.name.end_with?("\0") }.
-        map(&:to_specs).
-        flatten
+        incompatibility.terms.each do |term|
+          name = term.package.name
+          names_to_unlock << name if base_requirements[name]
+          next unless name == "bundler"
 
-      SpecSet.new(SpecSet.new(result).for(regular_requirements, false, @platforms))
-    rescue Molinillo::VersionConflict => e
-      conflicts = e.conflicts
+          no_versions_incompat = [cause.incompatibility, cause.satisfier].find {|incompat| incompat.cause.is_a?(PubGrub::Incompatibility::NoVersions) }
+          next unless no_versions_incompat
 
-      deps_to_unlock = conflicts.values.inject([]) do |deps, conflict|
-        deps |= conflict.requirement_trees.flatten.map {|req| base_requirements[req.name] }.compact
+          conflict_on_bundler ||= Gem::Requirement.new(no_versions_incompat.cause.constraint.constraint.constraint_string.split(","))
+        end
       end
 
-      if deps_to_unlock.any?
-        @base.unlock_deps(deps_to_unlock)
-        reset_spec_cache
+      if names_to_unlock.any?
+        @base.unlock_names(names_to_unlock)
         retry
       end
 
-      message = version_conflict_message(e)
-      raise VersionConflict.new(conflicts.keys.uniq, message)
-    rescue Molinillo::CircularDependencyError => e
-      names = e.dependencies.sort_by(&:name).map {|d| "gem '#{d.name}'" }
-      raise CyclicDependencyError, "Your bundle requires gems that depend" \
-        " on each other, creating an infinite loop. Please remove" \
-        " #{names.count > 1 ? "either " : ""}#{names.join(" or ")}" \
-        " and try again."
+      explanation = e.message
+
+      if conflict_on_bundler
+        explanation << "\n\n"
+        explanation << bundler_not_found_message(conflict_on_bundler)
+      end
+
+      raise SolveFailure.new(explanation)
+    end
+
+    def parse_dependency(package, dependency)
+      range = if repository_for(package).is_a?(Source::Gemspec)
+        PubGrub::VersionRange.any
+      else
+        requirement_to_range(dependency)
+      end
+
+      PubGrub::VersionConstraint.new(package, :range => range)
     end
 
-    include Molinillo::UI
-
-    # Conveys debug information to the user.
-    #
-    # @param [Integer] depth the current depth of the resolution process.
-    # @return [void]
-    def debug(depth = 0)
-      return unless debug?
-      debug_info = yield
-      debug_info = debug_info.inspect unless debug_info.is_a?(String)
-      puts debug_info.split("\n").map {|s| depth == 0 ? "BUNDLER: #{s}" : "BUNDLER(#{depth}): #{s}" }
+    def versions_for(package, range=VersionRange.any)
+      versions = range.select_versions(@sorted_versions[package])
+
+      sort_versions(package, versions)
+    end
+
+    def no_versions_incompatibility_for(package, unsatisfied_term)
+      cause = PubGrub::Incompatibility::NoVersions.new(unsatisfied_term)
+
+      custom_explanation = if package.name == "bundler"
+        "the current Bundler version (#{Bundler::VERSION}) does not satisfy #{cause.constraint}"
+      else
+        "#{cause.constraint} could not be found in #{repository_for(package)}"
+      end
+
+      PubGrub::Incompatibility.new([unsatisfied_term], :cause => cause, :custom_explanation => custom_explanation)
     end
 
     def debug?
-      return @debug_mode if defined?(@debug_mode)
-      @debug_mode =
-        ENV["BUNDLER_DEBUG_RESOLVER"] ||
+      ENV["BUNDLER_DEBUG_RESOLVER"] ||
         ENV["BUNDLER_DEBUG_RESOLVER_TREE"] ||
         ENV["DEBUG_RESOLVER"] ||
         ENV["DEBUG_RESOLVER_TREE"] ||
@@ -90,63 +137,87 @@ module Bundler
       Bundler.ui.info ""
     end
 
-    def indicate_progress
-      Bundler.ui.info ".", false unless debug?
-    end
+    def incompatibilities_for(package, version)
+      package_deps = @cached_dependencies[package]
+      sorted_versions = @sorted_versions[package]
+      package_deps[version].map do |dep_package, dep_constraint|
+        unless dep_constraint
+          # falsey indicates this dependency was invalid
+          cause = PubGrub::Incompatibility::InvalidDependency.new(dep_package, dep_constraint.constraint_string)
+          return [PubGrub::Incompatibility.new([PubGrub::Term.new(self_constraint, true)], :cause => cause)]
+        end
 
-    include Molinillo::SpecificationProvider
+        low = high = sorted_versions.index(version)
 
-    def dependencies_for(specification)
-      specification.dependencies_for_activated_platforms
-    end
+        # find version low such that all >= low share the same dep
+        while low > 0 && package_deps[sorted_versions[low - 1]][dep_package] == dep_constraint
+          low -= 1
+        end
+        low =
+          if low == 0
+            nil
+          else
+            sorted_versions[low]
+          end
 
-    def search_for(dependency)
-      @search_for[dependency] ||= begin
-        name = dependency.name
-        locked_results = @base[name].select {|spec| requirement_satisfied_by?(dependency, nil, spec) }
-        locked_requirement = base_requirements[name]
-        results = results_for(dependency) + locked_results
-        results = results.select {|spec| requirement_satisfied_by?(locked_requirement, nil, spec) } if locked_requirement
-        dep_platforms = dependency.gem_platforms(@platforms)
-
-        @gem_version_promoter.sort_versions(dependency, results).group_by(&:version).reduce([]) do |groups, (_, specs)|
-          relevant_platforms = dep_platforms.select {|platform| specs.any? {|spec| spec.match_platform(platform) } }
-          next groups unless relevant_platforms.any?
-
-          ruby_specs = select_best_platform_match(specs, Gem::Platform::RUBY)
-          if ruby_specs.any?
-            spec_group_ruby = SpecGroup.new(ruby_specs, [Gem::Platform::RUBY])
-            spec_group_ruby.force_ruby_platform = dependency.force_ruby_platform
-            groups << spec_group_ruby
+        # find version high such that all < high share the same dep
+        while high < sorted_versions.length && package_deps[sorted_versions[high]][dep_package] == dep_constraint
+          high += 1
+        end
+        high =
+          if high == sorted_versions.length
+            nil
+          else
+            sorted_versions[high]
           end
 
-          next groups if @resolving_only_for_ruby || dependency.force_ruby_platform
+        range = PubGrub::VersionRange.new(:min => low, :max => high, :include_min => true)
 
-          platform_specs = relevant_platforms.flat_map {|platform| select_best_platform_match(specs, platform) }
-          next groups if platform_specs == ruby_specs
+        self_constraint = PubGrub::VersionConstraint.new(package, :range => range)
 
-          spec_group = SpecGroup.new(platform_specs, relevant_platforms)
-          groups << spec_group
+        dep_term = PubGrub::Term.new(dep_constraint, false)
 
-          groups
+        custom_explanation = if dep_package.meta? && package.root?
+          "current #{dep_package} version is #{dep_constraint.constraint_string}"
         end
+
+        PubGrub::Incompatibility.new([PubGrub::Term.new(self_constraint, true), dep_term], :cause => :dependency, :custom_explanation => custom_explanation)
+      end
+    end
+
+    def all_versions_for(package)
+      name = package.name
+      results = @base[name] + results_for(name)
+      locked_requirement = base_requirements[name]
+      results = results.select {|spec| requirement_satisfied_by?(locked_requirement, spec) } if locked_requirement
+
+      versions = results.group_by(&:version).reduce([]) do |groups, (version, specs)|
+        platform_specs = package.platforms.flat_map {|platform| select_best_platform_match(specs, platform) }
+        next groups if platform_specs.empty?
+
+        ruby_specs = select_best_platform_match(specs, Gem::Platform::RUBY)
+        groups << Resolver::Candidate.new(version, :specs => ruby_specs) if ruby_specs.any?
+
+        next groups if platform_specs == ruby_specs
+
+        groups << Resolver::Candidate.new(version, :specs => platform_specs)
+
+        groups
       end
+
+      sort_versions(package, versions)
     end
 
-    def index_for(dependency)
-      source_for(dependency.name).specs
+    def index_for(name)
+      source_for(name).specs
     end
 
     def source_for(name)
       @source_requirements[name] || @source_requirements[:default]
     end
 
-    def results_for(dependency)
-      @results_for[dependency] ||= index_for(dependency).search(dependency)
-    end
-
-    def name_for(dependency)
-      dependency.name
+    def results_for(name)
+      index_for(name).search(name)
     end
 
     def name_for_explicit_dependency_source
@@ -155,107 +226,66 @@ module Bundler
       "Gemfile"
     end
 
-    def requirement_satisfied_by?(requirement, activated, spec)
-      requirement.matches_spec?(spec) || spec.source.is_a?(Source::Gemspec)
+    def requirement_satisfied_by?(requirement, spec)
+      requirement.satisfied_by?(spec.version) || spec.source.is_a?(Source::Gemspec)
     end
 
-    def sort_dependencies(dependencies, activated, conflicts)
-      dependencies.sort_by do |dependency|
-        name = name_for(dependency)
-        vertex = activated.vertex_named(name)
-        [
-          @base[name].any? ? 0 : 1,
-          vertex.payload ? 0 : 1,
-          vertex.root? ? 0 : 1,
-          amount_constrained(dependency),
-          conflicts[name] ? 0 : 1,
-          vertex.payload ? 0 : search_for(dependency).count,
-        ]
+    private
+
+    def sort_versions(package, versions)
+      if versions.size > 1
+        @gem_version_promoter.sort_versions(package, versions).reverse
+      else
+        versions
       end
     end
 
-    private
+    def repository_for(package)
+      source_for(package.name)
+    end
 
     def base_requirements
       @base.base_requirements
     end
 
-    def prerelease_specified
-      @gem_version_promoter.prerelease_specified
-    end
-
     def remove_from_candidates(spec)
       @base.delete(spec)
-
-      @results_for.keys.each do |dep|
-        next unless dep.name == spec.name
-
-        @results_for[dep].reject {|s| s.name == spec.name && s.version == spec.version }
-      end
-
-      reset_spec_cache
-    end
-
-    def reset_spec_cache
-      @search_for = {}
-      @gem_version_promoter.reset
-    end
-
-    # returns an integer \in (-\infty, 0]
-    # a number closer to 0 means the dependency is less constraining
-    #
-    # dependencies w/ 0 or 1 possibilities (ignoring version requirements)
-    # are given very negative values, so they _always_ sort first,
-    # before dependencies that are unconstrained
-    def amount_constrained(dependency)
-      @amount_constrained ||= {}
-      @amount_constrained[dependency.name] ||= if (base = @base[dependency.name]) && !base.empty?
-        dependency.requirement.satisfied_by?(base.first.version) ? 0 : 1
-      else
-        all = index_for(dependency).search(dependency.name).size
-
-        if all <= 1
-          all - 1_000_000
-        else
-          search = search_for(dependency)
-          search = prerelease_specified[dependency.name] ? search.count : search.count {|s| !s.version.prerelease? }
-          search - all
-        end
-      end
     end
 
-    def verify_gemfile_dependencies_are_found!(requirements)
-      requirements.map! do |requirement|
-        name = requirement.name
-        next requirement if name == "bundler"
-        next if requirement.gem_platforms(@platforms).empty?
-        next requirement unless search_for(requirement).empty?
-        next unless requirement.current_platform?
+    def prepare_dependencies(requirements, packages)
+      to_dependency_hash(requirements, packages).map do |dep_package, dep_constraint|
+        name = dep_package.name
+        next if dep_package.platforms.empty?
+        next [dep_package, dep_constraint] if name == "bundler"
+        next [dep_package, dep_constraint] unless versions_for(dep_package, dep_constraint.range).empty?
+        next unless dep_package.current_platform?
 
-        raise GemNotFound, gem_not_found_message(name, requirement, source_for(name))
-      end.compact!
+        raise GemNotFound, gem_not_found_message(dep_package, dep_constraint)
+      end.compact.to_h
     end
 
-    def gem_not_found_message(name, requirement, source, extra_message = "")
+    def gem_not_found_message(package, requirement)
+      name = package.name
+      source = source_for(name)
       specs = source.specs.search(name).sort_by {|s| [s.version, s.platform.to_s] }
       matching_part = name
-      requirement_label = SharedHelpers.pretty_dependency(requirement)
+      requirement_label = SharedHelpers.pretty_dependency(package.dependency)
       cache_message = begin
                           " or in gems cached in #{Bundler.settings.app_cache_path}" if Bundler.app_cache.exist?
                         rescue GemfileNotFound
                           nil
                         end
-      specs_matching_requirement = specs.select {| spec| requirement.matches_spec?(spec) }
+      specs_matching_requirement = specs.select {| spec| requirement_satisfied_by?(package.dependency.requirement, spec) }
 
       if specs_matching_requirement.any?
         specs = specs_matching_requirement
         matching_part = requirement_label
-        platforms = requirement.gem_platforms(@platforms)
+        platforms = package.platforms
         platform_label = platforms.size == 1 ? "platform '#{platforms.first}" : "platforms '#{platforms.join("', '")}"
         requirement_label = "#{requirement_label}' with #{platform_label}"
       end
 
-      message = String.new("Could not find gem '#{requirement_label}'#{extra_message} in #{source}#{cache_message}.\n")
+      message = String.new("Could not find gem '#{requirement_label}' in #{source}#{cache_message}.\n")
 
       if specs.any?
         message << "\nThe source contains the following gems matching '#{matching_part}':\n"
@@ -265,116 +295,62 @@ module Bundler
       message
     end
 
-    def version_conflict_message(e)
-      # only show essential conflicts, if possible
-      conflicts = e.conflicts.dup
-
-      if conflicts["bundler"]
-        conflicts.replace("bundler" => conflicts["bundler"])
-      else
-        conflicts.delete_if do |_name, conflict|
-          deps = conflict.requirement_trees.map(&:last).flatten(1)
-          !Bundler::VersionRanges.empty?(*Bundler::VersionRanges.for_many(deps.map(&:requirement)))
+    def requirement_to_range(requirement)
+      ranges = requirement.requirements.map do |(op, version)|
+        ver = Resolver::Candidate.new(version)
+
+        case op
+        when "~>"
+          name = "~> #{ver}"
+          bump = Resolver::Candidate.new(version.bump.to_s + ".A")
+          PubGrub::VersionRange.new(:name => name, :min => ver, :max => bump, :include_min => true)
+        when ">"
+          PubGrub::VersionRange.new(:min => ver)
+        when ">="
+          PubGrub::VersionRange.new(:min => ver, :include_min => true)
+        when "<"
+          PubGrub::VersionRange.new(:max => ver)
+        when "<="
+          PubGrub::VersionRange.new(:max => ver, :include_max => true)
+        when "="
+          PubGrub::VersionRange.new(:min => ver, :max => ver, :include_min => true, :include_max => true)
+        when "!="
+          PubGrub::VersionRange.new(:min => ver, :max => ver, :include_min => true, :include_max => true).invert
+        else
+          raise "bad version specifier: #{op}"
         end
       end
 
-      e = Molinillo::VersionConflict.new(conflicts, e.specification_provider) unless conflicts.empty?
-
-      e.message_with_trees(
-        :full_message_for_conflict => lambda do |name, conflict|
-          trees = conflict.requirement_trees
-
-          # called first, because we want to reduce the amount of work required to find maximal empty sets
-          trees = trees.uniq {|t| t.flatten.map {|dep| [dep.name, dep.requirement] } }
-
-          # bail out if tree size is too big for Array#combination to make any sense
-          if trees.size <= 15
-            maximal = 1.upto(trees.size).map do |size|
-              trees.map(&:last).flatten(1).combination(size).to_a
-            end.flatten(1).select do |deps|
-              Bundler::VersionRanges.empty?(*Bundler::VersionRanges.for_many(deps.map(&:requirement)))
-            end.min_by(&:size)
+      ranges.inject(&:intersect)
+    end
 
-            trees.reject! {|t| !maximal.include?(t.last) } if maximal
+    def to_dependency_hash(dependencies, packages)
+      dependencies.inject({}) do |deps, dep|
+        package = packages[dep.name]
 
-            trees.sort_by! {|t| t.reverse.map(&:name) }
-          end
+        current_req = deps[package]
+        new_req = parse_dependency(package, dep.requirement)
 
-          if trees.size > 1 || name == "bundler"
-            o = if name.end_with?("\0")
-              String.new("Bundler found conflicting requirements for the #{name} version:")
-            else
-              String.new("Bundler could not find compatible versions for gem \"#{name}\":")
-            end
-            o << %(\n)
-            o << %(  In #{name_for_explicit_dependency_source}:\n)
-            o << trees.map do |tree|
-              t = "".dup
-              depth = 2
-
-              base_tree = tree.first
-              base_tree_name = base_tree.name
-
-              if base_tree_name.end_with?("\0")
-                t = nil
-              else
-                tree.each do |req|
-                  t << "  " * depth << SharedHelpers.pretty_dependency(req)
-                  unless tree.last == req
-                    if spec = conflict.activated_by_name[req.name]
-                      t << %( was resolved to #{spec.version}, which)
-                    end
-                    t << %( depends on)
-                  end
-                  t << %(\n)
-                  depth += 1
-                end
-              end
-              t
-            end.compact.join("\n")
-          else
-            o = String.new
-          end
+        deps[package] = if current_req
+          current_req.intersect(new_req)
+        else
+          new_req
+        end
 
-          if name == "bundler"
-            o << %(\n  Current Bundler version:\n    bundler (#{Bundler::VERSION}))
-
-            conflict_dependency = conflict.requirement
-            conflict_requirement = conflict_dependency.requirement
-            other_bundler_required = !conflict_requirement.satisfied_by?(Gem::Version.new(Bundler::VERSION))
-
-            if other_bundler_required
-              o << "\n\n"
-
-              candidate_specs = source_for(:default_bundler).specs.search(conflict_dependency)
-              if candidate_specs.any?
-                target_version = candidate_specs.last.version
-                new_command = [File.basename($PROGRAM_NAME), "_#{target_version}_", *ARGV].join(" ")
-                o << "Your bundle requires a different version of Bundler than the one you're running.\n"
-                o << "Install the necessary version with `gem install bundler:#{target_version}` and rerun bundler using `#{new_command}`\n"
-              else
-                o << "Your bundle requires a different version of Bundler than the one you're running, and that version could not be found.\n"
-              end
-            end
-          elsif name.end_with?("\0")
-            o << %(\n  Current #{name} version:\n    #{SharedHelpers.pretty_dependency(@metadata_requirements.find {|req| req.name == name })}\n\n)
-          elsif !conflict.existing
-            o << "\n"
-
-            relevant_source = conflict.requirement.source || source_for(name)
-
-            extra_message = if trees.first.size > 1
-              ", which is required by gem '#{SharedHelpers.pretty_dependency(trees.first[-2])}',"
-            else
-              ""
-            end
-
-            o << gem_not_found_message(name, conflict.requirement, relevant_source, extra_message)
-          end
+        deps
+      end
+    end
 
-          o
-        end
-      )
+    def bundler_not_found_message(conflict_dependency)
+      candidate_specs = source_for(:default_bundler).specs.search("bundler").select {|spec| requirement_satisfied_by?(conflict_dependency, spec) }
+      if candidate_specs.any?
+        target_version = candidate_specs.last.version
+        new_command = [File.basename($PROGRAM_NAME), "_#{target_version}_", *ARGV].join(" ")
+        "Your bundle requires a different version of Bundler than the one you're running.\n" \
+        "Install the necessary version with `gem install bundler:#{target_version}` and rerun bundler using `#{new_command}`\n"
+      else
+        "Your bundle requires a different version of Bundler than the one you're running, and that version could not be found.\n"
+      end
     end
   end
 end