# class Gem::Resolver

Given a set of Gem::Dependency objects as `needed` and a way to query the set of available specs via `set`, calculates a set of ActivationRequest objects which indicate all the specs that should be activated to meet the all the requirements.

### Constants

DEBUG_RESOLVER

  If the DEBUG_RESOLVER environment variable is set then debugging mode is enabled for the resolver. This will display information about the state of the resolver while a set of dependencies is being resolved.

SINGLE_POSSIBILITY_CONSTRAINT_PENALTY

### Attributes

development[RW]

Set to true if all development dependencies should be considered.

development_shallow[RW]

Set to true if immediate development dependencies should be considered.

ignore_dependencies[RW]

When true, no dependencies are looked up for requested gems.

missing[R]

List of dependencies that could not be found in the configured sources.

skip_gems[RW]

Hash of gems to skip resolution. Keyed by gem name, with arrays of gem specifications as values.

soft_missing[RW]

When a missing dependency, don't stop. Just go on and record what was missing.

stats[R]

### Public Class Methods

compose_sets(*sets) click to toggle source

Combines `sets` into a ComposedSet that allows specification lookup in a uniform manner. If one of the `sets` is itself a ComposedSet its sets are flattened into the result ComposedSet.

    # File lib/rubygems/resolver.rb, line 61
    def self.compose_sets *sets
      sets.compact!

      sets = sets.map do |set|
        case set
        when Gem::Resolver::BestSet then
          set
        when Gem::Resolver::ComposedSet then
          set.sets
        else
          set
        end
      end.flatten

      case sets.length
      when 0 then
        raise ArgumentError, 'one set in the composition must be non-nil'
      when 1 then
        sets.first
      else
        Gem::Resolver::ComposedSet.new(*sets)
      end
    end

for_current_gems(needed) click to toggle source

Creates a Resolver that queries only against the already installed gems for the `needed` dependencies.

    # File lib/rubygems/resolver.rb, line 89
    def self.for_current_gems needed
      new needed, Gem::Resolver::CurrentSet.new
    end

new(needed, set = nil) click to toggle source

Create Resolver object which will resolve the tree starting with `needed` Dependency objects.

`set` is an object that provides where to look for specifications to satisfy the Dependencies. This defaults to IndexSet, which will query rubygems.org.

    # File lib/rubygems/resolver.rb, line 101
    def initialize needed, set = nil
      @set = set || Gem::Resolver::IndexSet.new
      @needed = needed

      @development         = false
      @development_shallow = false
      @ignore_dependencies = false
      @missing             = []
      @skip_gems           = {}
      @soft_missing        = false
      @stats               = Gem::Resolver::Stats.new
    end

### Public Instance Methods

allow_missing?(dependency) click to toggle source

    # File lib/rubygems/resolver.rb, line 270
    def allow_missing?(dependency)
      @missing << dependency
      @soft_missing
    end

debug?() click to toggle source

    # File lib/rubygems/resolver.rb, line 176
    def debug?
      DEBUG_RESOLVER
    end

dependencies_for(specification) click to toggle source

    # File lib/rubygems/resolver.rb, line 256
    def dependencies_for(specification)
      return [] if @ignore_dependencies
      spec = specification.spec
      requests(spec, specification)
    end

name_for(dependency) click to toggle source

    # File lib/rubygems/resolver.rb, line 266
    def name_for(dependency)
      dependency.name
    end

output() click to toggle source

    # File lib/rubygems/resolver.rb, line 172
    def output
      @output ||= debug? ? $stdout : File.open(Gem::Util::NULL_DEVICE, 'w')
    end

requirement_satisfied_by?(requirement, activated, spec) click to toggle source

    # File lib/rubygems/resolver.rb, line 262
    def requirement_satisfied_by?(requirement, activated, spec)
      requirement.matches_spec? spec
    end

resolve() click to toggle source

Proceed with resolution! Returns an array of ActivationRequest objects.

    # File lib/rubygems/resolver.rb, line 185
    def resolve
      locking_dg = Molinillo::DependencyGraph.new
      Molinillo::Resolver.new(self, self).resolve(@needed.map { |d| DependencyRequest.new d, nil }, locking_dg).tsort.map(&:payload).compact
    rescue Molinillo::VersionConflict => e
      conflict = e.conflicts.values.first
      raise Gem::DependencyResolutionError, Conflict.new(conflict.requirement_trees.first.first, conflict.existing, conflict.requirement)
    ensure
      @output.close if defined?(@output) and !debug?
    end

search_for(dependency) click to toggle source

    # File lib/rubygems/resolver.rb, line 224
    def search_for(dependency)
      possibles, all = find_possible(dependency)
      if !@soft_missing && possibles.empty?
        @missing << dependency
        exc = Gem::UnsatisfiableDependencyError.new dependency, all
        exc.errors = @set.errors
        raise exc
      end

      sources = []

      groups = Hash.new { |hash, key| hash[key] = [] }

      # create groups & sources in the same loop
      sources = possibles.map { |spec|
        source = spec.source
        groups[source] << spec
        source
      }.uniq.reverse

      activation_requests = []

      sources.each do |source|
        groups[source].
          sort_by { |spec| [spec.version, Gem::Platform.local =~ spec.platform ? 1 : 0] }.
          map { |spec| ActivationRequest.new spec, dependency, [] }.
          each { |activation_request| activation_requests << activation_request }
      end

      activation_requests
    end

sort_dependencies(dependencies, activated, conflicts) click to toggle source

    # File lib/rubygems/resolver.rb, line 275
    def sort_dependencies(dependencies, activated, conflicts)
      dependencies.sort_by.with_index do |dependency, i|
        name = name_for(dependency)
        [
          activated.vertex_named(name).payload ? 0 : 1,
          amount_constrained(dependency),
          conflicts[name] ? 0 : 1,
          activated.vertex_named(name).payload ? 0 : search_for(dependency).count,
          i # for stable sort
        ]
      end
    end

### Private Instance Methods

amount_constrained(dependency) click to toggle source

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

    # File lib/rubygems/resolver.rb, line 297
    def amount_constrained(dependency)
      @amount_constrained ||= {}
      @amount_constrained[dependency.name] ||= begin
        name_dependency = Gem::Dependency.new(dependency.name)
        dependency_request_for_name = Gem::Resolver::DependencyRequest.new(name_dependency, dependency.requester)
        all = @set.find_all(dependency_request_for_name).size

        if all <= 1
          all - SINGLE_POSSIBILITY_CONSTRAINT_PENALTY
        else
          search = search_for(dependency).size
          search - all
        end
      end
    end