1 files changed, 206 insertions, 0 deletions
diff --git a/lib/rubygems/commands/dependency_command.rb b/lib/rubygems/commands/dependency_command.rb
new file mode 100644
index 0000000000..9aaefae999
--- /dev/null
+++ b/lib/rubygems/commands/dependency_command.rb
@@ -0,0 +1,206 @@
+# frozen_string_literal: true
+
+require_relative "../command"
+require_relative "../local_remote_options"
+require_relative "../version_option"
+
+class Gem::Commands::DependencyCommand < Gem::Command
+  include Gem::LocalRemoteOptions
+  include Gem::VersionOption
+
+  def initialize
+    super "dependency",
+          "Show the dependencies of an installed gem",
+          version: Gem::Requirement.default, domain: :local
+
+    add_version_option
+    add_platform_option
+    add_prerelease_option
+
+    add_option("-R", "--[no-]reverse-dependencies",
+               "Include reverse dependencies in the output") do |value, options|
+      options[:reverse_dependencies] = value
+    end
+
+    add_option("-p", "--pipe",
+               "Pipe Format (name --version ver)") do |value, options|
+      options[:pipe_format] = value
+    end
+
+    add_local_remote_options
+  end
+
+  def arguments # :nodoc:
+    "REGEXP        show dependencies for gems whose names start with REGEXP"
+  end
+
+  def defaults_str # :nodoc:
+    "--local --version '#{Gem::Requirement.default}' --no-reverse-dependencies"
+  end
+
+  def description # :nodoc:
+    <<-EOF
+The dependency commands lists which other gems a given gem depends on.  For
+local gems only the reverse dependencies can be shown (which gems depend on
+the named gem).
+
+The dependency list can be displayed in a format suitable for piping for
+use with other commands.
+    EOF
+  end
+
+  def usage # :nodoc:
+    "#{program_name} REGEXP"
+  end
+
+  def fetch_remote_specs(name, requirement, prerelease) # :nodoc:
+    fetcher = Gem::SpecFetcher.fetcher
+
+    specs_type = prerelease ? :complete : :released
+
+    ss = if name.nil?
+      fetcher.detect(specs_type) { true }
+    else
+      fetcher.detect(specs_type) do |name_tuple|
+        name === name_tuple.name && requirement.satisfied_by?(name_tuple.version)
+      end
+    end
+
+    ss.map {|tuple, source| source.fetch_spec(tuple) }
+  end
+
+  def fetch_specs(name_pattern, requirement, prerelease) # :nodoc:
+    specs = []
+
+    if local?
+      specs.concat Gem::Specification.stubs.find_all {|spec|
+        name_matches = name_pattern ? name_pattern =~ spec.name : true
+        version_matches = requirement.satisfied_by?(spec.version)
+
+        name_matches && version_matches
+      }.map(&:to_spec)
+    end
+
+    specs.concat fetch_remote_specs name_pattern, requirement, prerelease if remote?
+
+    ensure_specs specs
+
+    specs.uniq.sort
+  end
+
+  def display_pipe(specs) # :nodoc:
+    specs.each do |spec|
+      next if spec.dependencies.empty?
+      spec.dependencies.sort_by(&:name).each do |dep|
+        say "#{dep.name} --version '#{dep.requirement}'"
+      end
+    end
+  end
+
+  def display_readable(specs, reverse) # :nodoc:
+    response = String.new
+
+    specs.each do |spec|
+      response << print_dependencies(spec)
+      unless reverse[spec.full_name].empty?
+        response << "  Used by\n"
+        reverse[spec.full_name].each do |sp, dep|
+          response << "    #{sp} (#{dep})\n"
+        end
+      end
+      response << "\n"
+    end
+
+    say response
+  end
+
+  def execute
+    ensure_local_only_reverse_dependencies
+
+    pattern = name_pattern options[:args]
+    requirement = Gem::Requirement.new options[:version]
+
+    specs = fetch_specs pattern, requirement, options[:prerelease]
+
+    reverse = reverse_dependencies specs
+
+    if options[:pipe_format]
+      display_pipe specs
+    else
+      display_readable specs, reverse
+    end
+  end
+
+  def ensure_local_only_reverse_dependencies # :nodoc:
+    if options[:reverse_dependencies] && remote? && !local?
+      alert_error "Only reverse dependencies for local gems are supported."
+      terminate_interaction 1
+    end
+  end
+
+  def ensure_specs(specs) # :nodoc:
+    return unless specs.empty?
+
+    patterns = options[:args].join ","
+    say "No gems found matching #{patterns} (#{options[:version]})" if
+      Gem.configuration.verbose
+
+    terminate_interaction 1
+  end
+
+  def print_dependencies(spec, level = 0) # :nodoc:
+    response = String.new
+    response << "  " * level + "Gem #{spec.full_name}\n"
+    unless spec.dependencies.empty?
+      spec.dependencies.sort_by(&:name).each do |dep|
+        response << "  " * level + "  #{dep}\n"
+      end
+    end
+    response
+  end
+
+  def reverse_dependencies(specs) # :nodoc:
+    reverse = Hash.new {|h, k| h[k] = [] }
+
+    return reverse unless options[:reverse_dependencies]
+
+    specs.each do |spec|
+      reverse[spec.full_name] = find_reverse_dependencies spec
+    end
+
+    reverse
+  end
+
+  ##
+  # Returns an Array of [specification, dep] that are satisfied by +spec+.
+
+  def find_reverse_dependencies(spec) # :nodoc:
+    result = []
+
+    Gem::Specification.each do |sp|
+      sp.dependencies.each do |dep|
+        dep = Gem::Dependency.new(*dep) unless Gem::Dependency === dep
+
+        if spec.name == dep.name &&
+           dep.requirement.satisfied_by?(spec.version)
+          result << [sp.full_name, dep]
+        end
+      end
+    end
+
+    result
+  end
+
+  private
+
+  def name_pattern(args)
+    return if args.empty?
+
+    if args.length == 1 && args.first =~ /\A(.*)(i)?\z/m
+      flags = $2 ? Regexp::IGNORECASE : nil
+      Regexp.new $1, flags
+    else
+      /\A#{Regexp.union(*args)}/
+    end
+  end
+end