1 files changed, 156 insertions, 0 deletions
diff --git a/lib/rubygems/commands/specification_command.rb b/lib/rubygems/commands/specification_command.rb
new file mode 100644
index 0000000000..15e543f1a6
--- /dev/null
+++ b/lib/rubygems/commands/specification_command.rb
@@ -0,0 +1,156 @@
+# frozen_string_literal: true
+
+require_relative "../command"
+require_relative "../local_remote_options"
+require_relative "../version_option"
+require_relative "../package"
+
+class Gem::Commands::SpecificationCommand < Gem::Command
+  include Gem::LocalRemoteOptions
+  include Gem::VersionOption
+
+  def initialize
+    Gem.load_yaml
+
+    super "specification", "Display gem specification (in yaml)",
+          domain: :local, version: Gem::Requirement.default,
+          format: :yaml
+
+    add_version_option("examine")
+    add_platform_option
+    add_prerelease_option
+
+    add_option("--all", "Output specifications for all versions of",
+               "the gem") do |_value, options|
+      options[:all] = true
+    end
+
+    add_option("--ruby", "Output ruby format") do |_value, options|
+      options[:format] = :ruby
+    end
+
+    add_option("--yaml", "Output YAML format") do |_value, options|
+      options[:format] = :yaml
+    end
+
+    add_option("--marshal", "Output Marshal format") do |_value, options|
+      options[:format] = :marshal
+    end
+
+    add_local_remote_options
+  end
+
+  def arguments # :nodoc:
+    <<-ARGS
+GEM_OR_FILE   gem name or a .gem file to show the gemspec for
+FIELD         name of gemspec field to show
+    ARGS
+  end
+
+  def defaults_str # :nodoc:
+    "--local --version '#{Gem::Requirement.default}' --yaml"
+  end
+
+  def description # :nodoc:
+    <<-EOF
+The specification command allows you to extract the specification from
+a gem for examination.
+
+The specification can be output in YAML, ruby or Marshal formats.
+
+Specific fields in the specification can be extracted in YAML format:
+
+  $ gem spec rake summary
+  --- Ruby based make-like utility.
+  ...
+
+    EOF
+  end
+
+  def usage # :nodoc:
+    "#{program_name} [GEM_OR_FILE] [FIELD]"
+  end
+
+  def execute
+    specs = []
+    gem = options[:args].shift
+
+    unless gem
+      raise Gem::CommandLineError,
+            "Please specify a gem name or a .gem file on the command line"
+    end
+
+    case v = options[:version]
+    when String
+      req = Gem::Requirement.create v
+    when Gem::Requirement
+      req = v
+    else
+      raise Gem::CommandLineError, "Unsupported version type: '#{v}'"
+    end
+
+    if !req.none? && options[:all]
+      alert_error "Specify --all or -v, not both"
+      terminate_interaction 1
+    end
+
+    if options[:all]
+      dep = Gem::Dependency.new gem
+    else
+      dep = Gem::Dependency.new gem, req
+    end
+
+    field = get_one_optional_argument
+
+    raise Gem::CommandLineError, "--ruby and FIELD are mutually exclusive" if
+      field && options[:format] == :ruby
+
+    if local?
+      if File.exist? gem
+        begin
+          specs << Gem::Package.new(gem).spec
+        rescue StandardError
+          nil
+        end
+      end
+
+      if specs.empty?
+        specs.push(*dep.matching_specs)
+      end
+    end
+
+    if remote?
+      dep.prerelease = options[:prerelease]
+      found, _ = Gem::SpecFetcher.fetcher.spec_for_dependency dep
+
+      specs.push(*found.map {|spec,| spec })
+    end
+
+    if specs.empty?
+      alert_error "No gem matching '#{dep}' found"
+      terminate_interaction 1
+    end
+
+    platform = get_platform_from_requirements(options)
+
+    if platform
+      specs = specs.select {|s| s.platform.to_s == platform }
+    end
+
+    unless options[:all]
+      specs = [specs.max_by(&:version)]
+    end
+
+    specs.each do |s|
+      s = s.send field if field
+
+      say case options[:format]
+          when :ruby then s.to_ruby
+          when :marshal then Marshal.dump s
+          else Gem.use_psych? ? s.to_yaml : Gem::YAMLSerializer.dump(s)
+      end
+
+      say "\n"
+    end
+  end
+end