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require 'set'
# This is the latest iteration of the gem dependency resolving algorithm. As of now,
# it can resolve (as a success or failure) any set of gem dependencies we throw at it
# in a reasonable amount of time. The most iterations I've seen it take is about 150.
# The actual implementation of the algorithm is not as good as it could be yet, but that
# can come later.
# Extending Gem classes to add necessary tracking information
module Gem
class Dependency
def required_by
@required_by ||= []
end
end
class Specification
def required_by
@required_by ||= []
end
end
end
module Bundler
class Resolver
attr_reader :errors
# Figures out the best possible configuration of gems that satisfies
# the list of passed dependencies and any child dependencies without
# causing any gem activation errors.
#
# ==== Parameters
# *dependencies<Gem::Dependency>:: The list of dependencies to resolve
#
# ==== Returns
# <GemBundle>,nil:: If the list of dependencies can be resolved, a
# collection of gemspecs is returned. Otherwise, nil is returned.
def self.resolve(requirements, index, source_requirements = {}, base = [])
resolver = new(index, source_requirements)
result = catch(:success) do
activated = {}
base.each { |s| activated[s.name] = s }
resolver.resolve(requirements, activated)
raise VersionConflict, "No compatible versions could be found for required dependencies:\n #{resolver.error_message}"
nil
end
SpecSet.new(result.values)
end
def initialize(index, source_requirements)
@errors = {}
@stack = []
@index = index
@source_requirements = source_requirements
end
def debug
if ENV['DEBUG_RESOLVER']
debug_info = yield
debug_info = debug_info.inpsect unless debug_info.is_a?(String)
$stderr.puts debug_info
end
end
def resolve(reqs, activated)
# If the requirements are empty, then we are in a success state. Aka, all
# gem dependencies have been resolved.
throw :success, activated if reqs.empty?
debug { print "\e[2J\e[f" ; "==== Iterating ====\n\n" }
# Sort dependencies so that the ones that are easiest to resolve are first.
# Easiest to resolve is defined by:
# 1) Is this gem already activated?
# 2) Do the version requirements include prereleased gems?
# 3) Sort by number of gems available in the source.
reqs = reqs.sort_by do |a|
[ activated[a.name] ? 0 : 1,
a.requirement.prerelease? ? 0 : 1,
@errors[a.name] ? 0 : 1,
activated[a.name] ? 0 : search(a).size ]
end
debug { "Activated:\n" + activated.values.map { |a| " #{a.name} (#{a.version})" }.join("\n") }
debug { "Requirements:\n" + reqs.map { |r| " #{r.name} (#{r.requirement})"}.join("\n") }
activated = activated.dup
if reqs.first.name == "bundler" && !activated["bundler"]
# activate the current version of bundler before other versions
bundler_version = ENV["BUNDLER_VERSION"] || Bundler::VERSION
current = Gem::Dependency.new("bundler", bundler_version, reqs.first.type)
else
# Pull off the first requirement so that we can resolve it
current = reqs.shift
end
debug { "Attempting:\n #{current.name} (#{current.requirement})"}
# Check if the gem has already been activated, if it has, we will make sure
# that the currently activated gem satisfies the requirement.
if existing = activated[current.name]
if current.requirement.satisfied_by?(existing.version)
debug { " * [SUCCESS] Already activated" }
@errors.delete(existing.name)
# Since the current requirement is satisfied, we can continue resolving
# the remaining requirements.
resolve(reqs, activated)
else
debug { " * [FAIL] Already activated" }
@errors[existing.name] = [existing, current]
debug { current.required_by.map {|d| " * #{d.name} (#{d.requirement})" }.join("\n") }
# debug { " * All current conflicts:\n" + @errors.keys.map { |c| " - #{c}" }.join("\n") }
# Since the current requirement conflicts with an activated gem, we need
# to backtrack to the current requirement's parent and try another version
# of it (maybe the current requirement won't be present anymore). If the
# current requirement is a root level requirement, we need to jump back to
# where the conflicting gem was activated.
parent = current.required_by.last
# `existing` could not respond to required_by if it is part of the base set
# of specs that was passed to the resolver (aka, instance of LazySpecification)
parent ||= existing.required_by.last if existing.respond_to?(:required_by)
# We track the spot where the current gem was activated because we need
# to keep a list of every spot a failure happened.
debug { " -> Jumping to: #{parent.name}" }
if parent
throw parent.name, existing.respond_to?(:required_by) && existing.required_by.last.name
else
# The original set of dependencies conflict with the base set of specs
# passed to the resolver. This is by definition an impossible resolve.
raise VersionConflict, "No compatible versions could be found for required dependencies:\n #{error_message}"
end
end
else
# There are no activated gems for the current requirement, so we are going
# to find all gems that match the current requirement and try them in decending
# order. We also need to keep a set of all conflicts that happen while trying
# this gem. This is so that if no versions work, we can figure out the best
# place to backtrack to.
conflicts = Set.new
# Fetch all gem versions matching the requirement
#
# TODO: Warn / error when no matching versions are found.
matching_versions = search(current)
if matching_versions.empty?
if current.required_by.empty?
if current.source
name = current.name
versions = @source_requirements[name][name].map { |s| s.version }
message = "Could not find gem '#{current}' in #{current.source}.\n"
if versions.any?
message << "Source contains '#{name}' at: #{versions.join(', ')}"
else
message << "Source does not contain any versions of '#{current}'"
end
else
message = "Could not find gem '#{current}' "
if @index.sources.include?(Bundler::Source::Rubygems)
message << "in any of the gem sources."
else
message << "in the gems available on this machine."
end
end
raise GemNotFound, message
else
@errors[current.name] = [nil, current]
end
end
matching_versions.reverse_each do |spec|
conflict = resolve_requirement(spec, current, reqs.dup, activated.dup)
conflicts << conflict if conflict
end
# If the current requirement is a root level gem and we have conflicts, we
# can figure out the best spot to backtrack to.
if current.required_by.empty? && !conflicts.empty?
# Check the current "catch" stack for the first one that is included in the
# conflicts set. That is where the parent of the conflicting gem was required.
# By jumping back to this spot, we can try other version of the parent of
# the conflicting gem, hopefully finding a combination that activates correctly.
@stack.reverse_each do |savepoint|
if conflicts.include?(savepoint)
debug { " -> Jumping to: #{savepoint}" }
throw savepoint
end
end
end
end
end
def resolve_requirement(spec, requirement, reqs, activated)
# We are going to try activating the spec. We need to keep track of stack of
# requirements that got us to the point of activating this gem.
spec.required_by.replace requirement.required_by
spec.required_by << requirement
activated[spec.name] = spec
debug { " Activating: #{spec.name} (#{spec.version})" }
debug { spec.required_by.map { |d| " * #{d.name} (#{d.requirement})" }.join("\n") }
# Now, we have to loop through all child dependencies and add them to our
# array of requirements.
debug { " Dependencies"}
spec.dependencies.each do |dep|
next if dep.type == :development
debug { " * #{dep.name} (#{dep.requirement})" }
dep.required_by.replace(requirement.required_by)
dep.required_by << requirement
reqs << dep
end
# We create a savepoint and mark it by the name of the requirement that caused
# the gem to be activated. If the activated gem ever conflicts, we are able to
# jump back to this point and try another version of the gem.
length = @stack.length
@stack << requirement.name
retval = catch(requirement.name) do
resolve(reqs, activated)
end
# Since we're doing a lot of throw / catches. A push does not necessarily match
# up to a pop. So, we simply slice the stack back to what it was before the catch
# block.
@stack.slice!(length..-1)
retval
end
def search(dep)
index = @source_requirements[dep.name] || @index
index.search(dep)
end
def error_message
output = errors.inject("") do |o, (conflict, (origin, requirement))|
if origin
o << " Conflict on: #{conflict.inspect}:\n"
if origin.respond_to?(:required_by) && required_by = origin.required_by.first
o << " * #{conflict} (#{origin.version}) activated by #{required_by}\n"
else
o << " * #{conflict} (#{origin.version}) in Gemfile.lock\n"
end
o << " * #{requirement} required"
if requirement.required_by.first
o << " by #{requirement.required_by.first}\n"
else
o << " in Gemfile\n"
end
else
o << " #{requirement} not found in any of the sources\n"
o << " required by #{requirement.required_by.first}\n"
end
o << " All possible versions of origin requirements conflict."
end
end
end
end
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