spec/ruby/language/predefined_spec.rb

require_relative '../spec_helper'
require 'stringio'

# The following tables are excerpted from Programming Ruby: The Pragmatic Programmer's Guide'
# Second Edition by Dave Thomas, Chad Fowler, and Andy Hunt, page 319-22.
#
# Entries marked [r/o] are read-only and an error will be raised of the program attempts to
# modify them. Entries marked [thread] are thread local.

# Exception Information
# ---------------------------------------------------------------------------------------------------
#
# $!               Exception       The exception object passed to raise. [thread]
# $@               Array           The stack backtrace generated by the last exception. [thread]

# Pattern Matching Variables
# ---------------------------------------------------------------------------------------------------
#
# These variables are set to nil after an unsuccessful pattern match.
#
# $&               String          The string matched (following a successful pattern match). This variable is
#                                  local to the current scope. [r/o, thread]
# $+               String          The contents of the highest-numbered group matched following a successful
#                                  pattern match. Thus, in "cat" =~/(c|a)(t|z)/, $+ will be set to “t”. This
#                                  variable is local to the current scope. [r/o, thread]
# $`               String          The string preceding the match in a successful pattern match. This variable
#                                  is local to the current scope. [r/o, thread]
# $'               String          The string following the match in a successful pattern match. This variable
#                                  is local to the current scope. [r/o, thread]
# $1 to $<N>       String          The contents of successive groups matched in a successful pattern match. In
#                                  "cat" =~/(c|a)(t|z)/, $1 will be set to “a” and $2 to “t”. This variable
#                                  is local to the current scope. [r/o, thread]
# $~               MatchData       An object that encapsulates the results of a successful pattern match. The
#                                  variables $&, $`, $', and $1 to $<N> are all derived from $~. Assigning to $~
#                                  changes the values of these derived variables. This variable is local to the
#                                  current scope. [thread]


describe "Predefined global $~" do
  it "is set to contain the MatchData object of the last match if successful" do
    md = /foo/.match 'foo'
    $~.should be_kind_of(MatchData)
    $~.should equal md

    /bar/ =~ 'bar'
    $~.should be_kind_of(MatchData)
    $~.should_not equal md
  end

  it "is set to nil if the last match was unsuccessful" do
    /foo/ =~ 'foo'
    $~.should_not.nil?

    /foo/ =~ 'bar'
    $~.should.nil?
  end

  it "is set at the method-scoped level rather than block-scoped" do
    obj = Object.new
    def obj.foo; yield; end
    def obj.foo2(&proc); proc.call; end

    match2 = nil
    match3 = nil
    match4 = nil

    match1 = /foo/.match "foo"

    obj.foo { match2 = /bar/.match("bar") }

    match2.should_not == nil
    $~.should == match2

    match3 = /baz/.match("baz")

    match3.should_not == nil
    $~.should == match3

    obj.foo2 { match4 = /qux/.match("qux") }

    match4.should_not == nil
    $~.should == match4
  end

  it "raises an error if assigned an object not nil or instanceof MatchData" do
    $~ = nil
    $~.should == nil
    $~ = /foo/.match("foo")
    $~.should be_an_instance_of(MatchData)

    -> { $~ = Object.new }.should raise_error(TypeError)
    -> { $~ = 1 }.should raise_error(TypeError)
  end

  it "changes the value of derived capture globals when assigned" do
    "foo" =~ /(f)oo/
    foo_match = $~
    "bar" =~ /(b)ar/
    $~ = foo_match
    $1.should == "f"
  end

  it "changes the value of the derived preceding match global" do
    "foo hello" =~ /hello/
    foo_match = $~
    "bar" =~ /(bar)/
    $~ = foo_match
    $`.should == "foo "
  end

  it "changes the value of the derived following match global" do
    "foo hello" =~ /foo/
    foo_match = $~
    "bar" =~ /(bar)/
    $~ = foo_match
    $'.should == " hello"
  end

  it "changes the value of the derived full match global" do
    "foo hello" =~ /foo/
    foo_match = $~
    "bar" =~ /(bar)/
    $~ = foo_match
    $&.should == "foo"
  end
end

describe "Predefined global $&" do
  it "is equivalent to MatchData#[0] on the last match $~" do
    /foo/ =~ 'barfoobaz'
    $&.should == $~[0]
    $&.should == 'foo'
  end

  it "sets the encoding to the encoding of the source String" do
    "abc".dup.force_encoding(Encoding::EUC_JP) =~ /b/
    $&.encoding.should equal(Encoding::EUC_JP)
  end
end

describe "Predefined global $`" do
  it "is equivalent to MatchData#pre_match on the last match $~" do
    /foo/ =~ 'barfoobaz'
    $`.should == $~.pre_match
    $`.should == 'bar'
  end

  it "sets the encoding to the encoding of the source String" do
    "abc".dup.force_encoding(Encoding::EUC_JP) =~ /b/
    $`.encoding.should equal(Encoding::EUC_JP)
  end

  it "sets an empty result to the encoding of the source String" do
    "abc".dup.force_encoding(Encoding::ISO_8859_1) =~ /a/
    $`.encoding.should equal(Encoding::ISO_8859_1)
  end
end

describe "Predefined global $'" do
  it "is equivalent to MatchData#post_match on the last match $~" do
    /foo/ =~ 'barfoobaz'
    $'.should == $~.post_match
    $'.should == 'baz'
  end

  it "sets the encoding to the encoding of the source String" do
    "abc".dup.force_encoding(Encoding::EUC_JP) =~ /b/
    $'.encoding.should equal(Encoding::EUC_JP)
  end

  it "sets an empty result to the encoding of the source String" do
    "abc".dup.force_encoding(Encoding::ISO_8859_1) =~ /c/
    $'.encoding.should equal(Encoding::ISO_8859_1)
  end
end

describe "Predefined global $+" do
  it "is equivalent to $~.captures.last" do
    /(f(o)o)/ =~ 'barfoobaz'
    $+.should == $~.captures.last
    $+.should == 'o'
  end

  it "captures the last non nil capture" do
    /(a)|(b)/ =~ 'a'
    $+.should == 'a'
  end

  it "sets the encoding to the encoding of the source String" do
    "abc".dup.force_encoding(Encoding::EUC_JP) =~ /(b)/
    $+.encoding.should equal(Encoding::EUC_JP)
  end
end

describe "Predefined globals $1..N" do
  it "are equivalent to $~[N]" do
    /(f)(o)(o)/ =~ 'foo'
    $1.should == $~[1]
    $2.should == $~[2]
    $3.should == $~[3]
    $4.should == $~[4]

    [$1, $2, $3, $4].should == ['f', 'o', 'o', nil]
  end

  it "are nil unless a match group occurs" do
    def test(arg)
      case arg
      when /-(.)?/
        $1
      end
    end
    test("-").should == nil
  end

  it "sets the encoding to the encoding of the source String" do
    "abc".dup.force_encoding(Encoding::EUC_JP) =~ /(b)/
    $1.encoding.should equal(Encoding::EUC_JP)
  end
end

describe "Predefined global $stdout" do
  before :each do
    @old_stdout = $stdout
  end

  after :each do
    $stdout = @old_stdout
  end

  it "raises TypeError error if assigned to nil" do
    -> { $stdout = nil }.should raise_error(TypeError)
  end

  it "raises TypeError error if assigned to object that doesn't respond to #write" do
    obj = mock('object')
    -> { $stdout = obj }.should raise_error(TypeError)

    obj.stub!(:write)
    $stdout = obj
    $stdout.should equal(obj)
  end
end

describe "Predefined global $!" do
  it "is Fiber-local" do
    Fiber.new do
      raise "hi"
    rescue
      Fiber.yield
    end.resume

    $!.should == nil
  end

  # See http://jira.codehaus.org/browse/JRUBY-5550
  it "remains nil after a failed core class \"checked\" coercion against a class that defines method_missing" do
    $!.should == nil

    obj = Class.new do
      def method_missing(*args)
        super
      end
    end.new

    [obj, 'foo'].join

    $!.should == nil
  end

  it "should be set to the value of $! before the begin after a successful rescue" do
    outer = StandardError.new 'outer'
    inner = StandardError.new 'inner'

    begin
      raise outer
    rescue
      $!.should == outer

      # nested rescue
      begin
        $!.should == outer
        raise inner
      rescue
        $!.should == inner
      ensure
        $!.should == outer
      end
      $!.should == outer
    end
    $!.should == nil
  end

  it "should be set to the value of $! before the begin after a rescue which returns" do
    def foo
      outer = StandardError.new 'outer'
      inner = StandardError.new 'inner'

      begin
        raise outer
      rescue
        $!.should == outer

        # nested rescue
        begin
          $!.should == outer
          raise inner
        rescue
          $!.should == inner
          return
        ensure
          $!.should == outer
        end
        $!.should == outer
      end
      $!.should == nil
    end
    foo
  end

  it "should be set to the value of $! before the begin after a successful rescue within an ensure" do
    outer = StandardError.new 'outer'
    inner = StandardError.new 'inner'

    begin
      begin
        raise outer
      ensure
        $!.should == outer

        # nested rescue
        begin
          $!.should == outer
          raise inner
        rescue
          $!.should == inner
        ensure
          $!.should == outer
        end
        $!.should == outer
      end
      flunk "outer should be raised after the ensure"
    rescue
      $!.should == outer
    end
    $!.should == nil
  end

  it "should be set to the new exception after a throwing rescue" do
    outer = StandardError.new 'outer'
    inner = StandardError.new 'inner'

    begin
      raise outer
    rescue
      $!.should == outer

      begin
        # nested rescue
        begin
          $!.should == outer
          raise inner
        rescue # the throwing rescue
          $!.should == inner
          raise inner
        ensure
          $!.should == inner
        end
      rescue # do not make the exception fail the example
        $!.should == inner
      end
      $!.should == outer
    end
    $!.should == nil
  end

  describe "in bodies without ensure" do
    it "should be cleared when an exception is rescued" do
      e = StandardError.new 'foo'
      begin
        raise e
      rescue
        $!.should == e
      end
      $!.should == nil
    end

    it "should be cleared when an exception is rescued even when a non-local return is present" do
      def foo(e)
        $!.should == e
        yield
      end
      def bar
        e = StandardError.new 'foo'
        begin
          raise e
        rescue
          $!.should == e
          foo(e) { return }
        end
      end

      bar
      $!.should == nil
    end

    it "should be cleared when an exception is rescued even when a non-local return from block" do
      def foo
        [ 1 ].each do
          begin
            raise StandardError.new('err')
          rescue => e
            $!.should == e
            return
          end
        end
      end

      foo
      $!.should == nil
    end

    it "should not be cleared when an exception is not rescued" do
      e = StandardError.new
      begin
        begin
          begin
            raise e
          rescue TypeError
            flunk
          end
        ensure
          $!.should == e
        end
      rescue
        $!.should == e
      end
      $!.should == nil
    end

    it "should not be cleared when an exception is rescued and rethrown" do
      e = StandardError.new 'foo'
      begin
        begin
          begin
            raise e
          rescue => e
            $!.should == e
            raise e
          end
        ensure
          $!.should == e
        end
      rescue
        $!.should == e
      end
      $!.should == nil
    end
  end

  describe "in ensure-protected bodies" do
    it "should be cleared when an exception is rescued" do
      e = StandardError.new 'foo'
      begin
        raise e
      rescue
        $!.should == e
      ensure
        $!.should == nil
      end
      $!.should == nil
    end

    it "should not be cleared when an exception is not rescued" do
      e = StandardError.new
      begin
        begin
          begin
            raise e
          rescue TypeError
            flunk
          ensure
            $!.should == e
          end
        ensure
          $!.should == e
        end
      rescue
        $!.should == e
      end
    end

    it "should not be cleared when an exception is rescued and rethrown" do
      e = StandardError.new
      begin
        begin
          begin
            raise e
          rescue => e
            $!.should == e
            raise e
          ensure
            $!.should == e
          end
        ensure
          $!.should == e
        end
      rescue
        $!.should == e
      end
    end
  end
end

# Input/Output Variables
# ---------------------------------------------------------------------------------------------------
#
# $/               String          The input record separator (newline by default). This is the value that rou-
#                                  tines such as Kernel#gets use to determine record boundaries. If set to
#                                  nil, gets will read the entire file.
# $-0              String          Synonym for $/.
# $\               String          The string appended to the output of every call to methods such as
#                                  Kernel#print and IO#write. The default value is nil.
# $,               String          The separator string output between the parameters to methods such as
#                                  Kernel#print and Array#join. Defaults to nil, which adds no text.
# $.               Integer          The number of the last line read from the current input file.
# $;               String          The default separator pattern used by String#split. May be set from the
#                                  command line using the -F flag.
# $<               Object          An object that provides access to the concatenation of the contents of all
#                                  the files given as command-line arguments or $stdin (in the case where
#                                  there are no arguments). $< supports methods similar to a File object:
#                                  binmode, close, closed?, each, each_byte, each_line, eof, eof?,
#                                  file, filename, fileno, getc, gets, lineno, lineno=, path, pos, pos=,
#                                  read, readchar, readline, readlines, rewind, seek, skip, tell, to_a,
#                                  to_i, to_io, to_s, along with the methods in Enumerable. The method
#                                  file returns a File object for the file currently being read. This may change
#                                  as $< reads through the files on the command line. [r/o]
# $>               IO              The destination of output for Kernel#print and Kernel#printf. The
#                                  default value is $stdout.
# $_               String          The last line read by Kernel#gets or Kernel#readline. Many string-
#                                  related functions in the Kernel module operate on $_ by default. The vari-
#                                  able is local to the current scope. [thread]
# $-F              String          Synonym for $;.
# $stderr          IO              The current standard error output.
# $stdin           IO              The current standard input.
# $stdout          IO              The current standard output. Assignment to $stdout is deprecated: use
#                                  $stdout.reopen instead.

describe "Predefined global $/" do
  before :each do
    @verbose, $VERBOSE = $VERBOSE, nil
    @dollar_slash = $/
    @dollar_dash_zero = $-0
  end

  after :each do
    $/ = @dollar_slash
    $-0 = @dollar_dash_zero
    $VERBOSE = @verbose
  end

  ruby_version_is ""..."3.5" do
    it "can be assigned a String" do
      str = +"abc"
      $/ = str
      $/.should equal(str)
    end
  end

  ruby_version_is "3.5" do
    it "makes a new frozen String from the assigned String" do
      string_subclass = Class.new(String)
      str = string_subclass.new("abc")
      str.instance_variable_set(:@ivar, 1)
      $/ = str
      $/.should.frozen?
      $/.should be_an_instance_of(String)
      $/.should_not.instance_variable_defined?(:@ivar)
      $/.should == str
    end

    it "makes a new frozen String if it's not frozen" do
      str = +"abc"
      $/ = str
      $/.should.frozen?
      $/.should == str
    end

    it "assigns the given String if it's frozen and has no instance variables" do
      str = "abc".freeze
      $/ = str
      $/.should equal(str)
    end
  end
  it "can be assigned nil" do
    $/ = nil
    $/.should be_nil
  end

  it "returns the value assigned" do
    ($/ = "xyz").should == "xyz"
  end

  it "changes $-0" do
    $/ = "xyz"
    $-0.should equal($/)
  end

  it "does not call #to_str to convert the object to a String" do
    obj = mock("$/ value")
    obj.should_not_receive(:to_str)

    -> { $/ = obj }.should raise_error(TypeError)
  end

  it "raises a TypeError if assigned an Integer" do
    -> { $/ = 1 }.should raise_error(TypeError)
  end

  it "raises a TypeError if assigned a boolean" do
    -> { $/ = true }.should raise_error(TypeError)
  end
end

describe "Predefined global $-0" do
  before :each do
    @verbose, $VERBOSE = $VERBOSE, nil
    @dollar_slash = $/
    @dollar_dash_zero = $-0
  end

  after :each do
    $/ = @dollar_slash
    $-0 = @dollar_dash_zero
    $VERBOSE = @verbose
  end

  ruby_version_is ""..."3.5" do
    it "can be assigned a String" do
      str = +"abc"
      $-0 = str
      $-0.should equal(str)
    end
  end

  ruby_version_is "3.5" do
    it "makes a new frozen String from the assigned String" do
      string_subclass = Class.new(String)
      str = string_subclass.new("abc")
      str.instance_variable_set(:@ivar, 1)
      $-0 = str
      $-0.should.frozen?
      $-0.should be_an_instance_of(String)
      $-0.should_not.instance_variable_defined?(:@ivar)
      $-0.should == str
    end

    it "makes a new frozen String if it's not frozen" do
      str = +"abc"
      $-0 = str
      $-0.should.frozen?
      $-0.should == str
    end

    it "assigns the given String if it's frozen and has no instance variables" do
      str = "abc".freeze
      $-0 = str
      $-0.should equal(str)
    end
  end

  it "can be assigned nil" do
    $-0 = nil
    $-0.should be_nil
  end

  it "returns the value assigned" do
    ($-0 = "xyz").should == "xyz"
  end

  it "changes $/" do
    $-0 = "xyz"
    $/.should equal($-0)
  end

  it "does not call #to_str to convert the object to a String" do
    obj = mock("$-0 value")
    obj.should_not_receive(:to_str)

    -> { $-0 = obj }.should raise_error(TypeError)
  end

  it "raises a TypeError if assigned an Integer" do
    -> { $-0 = 1 }.should raise_error(TypeError)
  end

  it "raises a TypeError if assigned a boolean" do
    -> { $-0 = true }.should raise_error(TypeError)
  end
end

describe "Predefined global $\\" do
  before :each do
    @verbose, $VERBOSE = $VERBOSE, nil
    @dollar_backslash = $\
  end

  after :each do
    $\ = @dollar_backslash
    $VERBOSE = @verbose
  end

  it "can be assigned a String" do
    str = "abc"
    $\ = str
    $\.should equal(str)
  end

  it "can be assigned nil" do
    $\ = nil
    $\.should be_nil
  end

  it "returns the value assigned" do
    ($\ = "xyz").should == "xyz"
  end

  it "does not call #to_str to convert the object to a String" do
    obj = mock("$\\ value")
    obj.should_not_receive(:to_str)

    -> { $\ = obj }.should raise_error(TypeError)
  end

  it "raises a TypeError if assigned not String" do
    -> { $\ = 1 }.should raise_error(TypeError)
    -> { $\ = true }.should raise_error(TypeError)
  end
end

describe "Predefined global $," do
  after :each do
    $, = nil
  end

  it "defaults to nil" do
    $,.should be_nil
  end

  it "raises TypeError if assigned a non-String" do
    -> { $, = Object.new }.should raise_error(TypeError)
  end

  it "warns if assigned non-nil" do
    -> { $, = "_" }.should complain(/warning: [`']\$,' is deprecated/)
  end
end

describe "Predefined global $." do
  it "can be assigned an Integer" do
    $. = 123
    $..should == 123
  end

  it "can be assigned a Float" do
    $. = 123.5
    $..should == 123
  end

  it "should call #to_int to convert the object to an Integer" do
    obj = mock("good-value")
    obj.should_receive(:to_int).and_return(321)

    $. = obj
    $..should == 321
  end

  it "raises TypeError if object can't be converted to an Integer" do
    obj = mock("bad-value")
    obj.should_receive(:to_int).and_return('abc')

    -> { $. = obj }.should raise_error(TypeError)
  end
end

describe "Predefined global $;" do
  after :each do
    $; = nil
  end

  it "warns if assigned non-nil" do
    -> { $; = "_" }.should complain(/warning: [`']\$;' is deprecated/)
  end
end

describe "Predefined global $_" do
  it "is set to the last line read by e.g. StringIO#gets" do
    stdin = StringIO.new("foo\nbar\n", "r")

    read = stdin.gets
    read.should == "foo\n"
    $_.should == read

    read = stdin.gets
    read.should == "bar\n"
    $_.should == read

    read = stdin.gets
    read.should == nil
    $_.should == read
  end

  it "is set at the method-scoped level rather than block-scoped" do
    obj = Object.new
    def obj.foo; yield; end
    def obj.foo2; yield; end

    stdin = StringIO.new("foo\nbar\nbaz\nqux\n", "r")
    match = stdin.gets

    obj.foo { match = stdin.gets }

    match.should == "bar\n"
    $_.should == match

    match = stdin.gets

    match.should == "baz\n"
    $_.should == match

    obj.foo2 { match = stdin.gets }

    match.should == "qux\n"
    $_.should == match
  end

  it "is Thread-local" do
    $_ = nil
    running = false

    thr = Thread.new do
      $_ = "last line"
      running = true
    end

    Thread.pass until running
    $_.should be_nil

    thr.join
  end

  it "can be assigned any value" do
    $_ = nil
    $_.should == nil
    $_ = "foo"
    $_.should == "foo"
    o = Object.new
    $_ = o
    $_.should == o
    $_ = 1
    $_.should == 1
  end
end

# Execution Environment Variables
# ---------------------------------------------------------------------------------------------------
#
# $0               String          The name of the top-level Ruby program being executed. Typically this will
#                                  be the program’s filename. On some operating systems, assigning to this
#                                  variable will change the name of the process reported (for example) by the
#                                  ps(1) command.
# $*               Array           An array of strings containing the command-line options from the invoca-
#                                  tion of the program. Options used by the Ruby interpreter will have been
#                                  removed. [r/o]
# $"               Array           An array containing the filenames of modules loaded by require. [r/o]
# $$               Integer          The process number of the program being executed. [r/o]
# $?               Process::Status The exit status of the last child process to terminate. [r/o, thread]
# $:               Array           An array of strings, where each string specifies a directory to be searched for
#                                  Ruby scripts and binary extensions used by the load and require methods.
#                                  The initial value is the value of the arguments passed via the -I command-
#                                  line option, followed by an installation-defined standard library location, fol-
#                                  lowed by the current directory (“.”). This variable may be set from within a
#                                  program to alter the default search path; typically, programs use $: << dir
#                                  to append dir to the path. [r/o]
# $-a              Object          True if the -a option is specified on the command line. [r/o]
# $-d              Object          Synonym for $DEBUG.
# $DEBUG           Object          Set to true if the -d command-line option is specified.
# __FILE__         String          The name of the current source file. [r/o]
# $F               Array           The array that receives the split input line if the -a command-line option is
#                                  used.
# $FILENAME        String          The name of the current input file. Equivalent to $<.filename. [r/o]
# $-i              String          If in-place edit mode is enabled (perhaps using the -i command-line
#                                  option), $-i holds the extension used when creating the backup file. If you
#                                  set a value into $-i, enables in-place edit mode.
# $-I              Array           Synonym for $:. [r/o]
# $-K              String          Sets the multibyte coding system for strings and regular expressions. Equiv-
#                                  alent to the -K command-line option.
# $-l              Object          Set to true if the -l option (which enables line-end processing) is present
#                                  on the command line. [r/o]
# __LINE__         String          The current line number in the source file. [r/o]
# $LOAD_PATH       Array           A synonym for $:. [r/o]
# $-p              Object          Set to true if the -p option (which puts an implicit while gets . . . end
#                                  loop around your program) is present on the command line. [r/o]
# $VERBOSE         Object          Set to true if the -v, --version, -W, or -w option is specified on the com-
#                                  mand line. Set to false if no option, or -W1 is given. Set to nil if -W0
#                                  was specified. Setting this option to true causes the interpreter and some
#                                  library routines to report additional information. Setting to nil suppresses
#                                  all warnings (including the output of Kernel.warn).
# $-v              Object          Synonym for $VERBOSE.
# $-w              Object          Synonym for $VERBOSE.
describe "Execution variable $:" do
  it "is initialized to an array of strings" do
    $:.is_a?(Array).should == true
    ($:.length > 0).should == true
  end

  it "does not include the current directory" do
    $:.should_not include(".")
  end

  it "is the same object as $LOAD_PATH and $-I" do
    $:.__id__.should == $LOAD_PATH.__id__
    $:.__id__.should == $-I.__id__
  end

  it "can be changed via <<" do
    $: << "foo"
    $:.should include("foo")
  ensure
    $:.delete("foo")
  end

  it "is read-only" do
    -> {
      $: = []
    }.should raise_error(NameError)

    -> {
      $LOAD_PATH = []
    }.should raise_error(NameError)

    -> {
      $-I = []
    }.should raise_error(NameError)
  end

  it "default $LOAD_PATH entries until sitelibdir included have @gem_prelude_index set" do
    skip "no sense in ruby itself" if MSpecScript.instance_variable_defined?(:@testing_ruby)

    $:.should.include?(RbConfig::CONFIG['sitelibdir'])
    idx = $:.index(RbConfig::CONFIG['sitelibdir'])

    $:[idx..-1].all? { |p| p.instance_variable_defined?(:@gem_prelude_index) }.should be_true
    $:[0...idx].all? { |p| !p.instance_variable_defined?(:@gem_prelude_index) }.should be_true
  end
end

describe "Global variable $\"" do
  it "is an alias for $LOADED_FEATURES" do
    $".should equal $LOADED_FEATURES
  end

  it "is read-only" do
    -> {
      $" = []
    }.should raise_error(NameError)

    -> {
      $LOADED_FEATURES = []
    }.should raise_error(NameError)
  end
end

describe "Global variable $<" do
  it "is read-only" do
    -> {
      $< = nil
    }.should raise_error(NameError)
  end
end

describe "Global variable $FILENAME" do
  it "is read-only" do
    -> {
      $FILENAME = "-"
    }.should raise_error(NameError)
  end
end

describe "Global variable $?" do
  it "is read-only" do
    -> {
      $? = nil
    }.should raise_error(NameError)
  end

  it "is thread-local" do
    system(ruby_cmd('exit 0'))
    Thread.new { $?.should be_nil }.join
  end
end

describe "Global variable $-a" do
  it "is read-only" do
    -> { $-a = true }.should raise_error(NameError)
  end
end

describe "Global variable $-l" do
  it "is read-only" do
    -> { $-l = true }.should raise_error(NameError)
  end
end

describe "Global variable $-p" do
  it "is read-only" do
    -> { $-p = true }.should raise_error(NameError)
  end
end

describe "Global variable $-d" do
  before :each do
    @debug = $DEBUG
  end

  after :each do
    $DEBUG = @debug
  end

  it "is an alias of $DEBUG" do
    $DEBUG = true
    $-d.should be_true
    $-d = false
    $DEBUG.should be_false
  end
end

describe "Global variable $VERBOSE" do
  before :each do
    @verbose = $VERBOSE
  end

  after :each do
    $VERBOSE = @verbose
  end

  it "is false by default" do
    $VERBOSE.should be_false
  end

  it "converts truthy values to true" do
    [true, 1, 0, [], ""].each do |true_value|
      $VERBOSE = true_value
      $VERBOSE.should be_true
    end
  end

  it "allows false" do
    $VERBOSE = false
    $VERBOSE.should be_false
  end

  it "allows nil without coercing to false" do
    $VERBOSE = nil
    $VERBOSE.should be_nil
  end
end

describe :verbose_global_alias, shared: true do
  before :each do
    @verbose = $VERBOSE
  end

  after :each do
    $VERBOSE = @verbose
  end

  it "is an alias of $VERBOSE" do
    $VERBOSE = true
    eval(@method).should be_true
    eval("#{@method} = false")
    $VERBOSE.should be_false
  end
end

describe "Global variable $-v" do
  it_behaves_like :verbose_global_alias, '$-v'
end

describe "Global variable $-w" do
  it_behaves_like :verbose_global_alias, '$-w'
end

describe "Global variable $0" do
  before :each do
    @orig_program_name = $0
  end

  after :each do
    $0 = @orig_program_name
  end

  it "is the path given as the main script and the same as __FILE__" do
    script = "fixtures/dollar_zero.rb"
    Dir.chdir(__dir__) do
      ruby_exe(script).should == "#{script}\n#{script}\nOK"
    end
  end

  it "returns the program name" do
    $0 = "rbx"
    $0.should == "rbx"
  end

  platform_is :linux, :darwin do
    it "actually sets the program name" do
      title = "rubyspec-dollar0-test"
      $0 = title
      `ps -ocommand= -p#{$$}`.should include(title)
    end
  end

  it "returns the given value when set" do
    ($0 = "rbx").should == "rbx"
  end

  it "raises a TypeError when not given an object that can be coerced to a String" do
    -> { $0 = nil }.should raise_error(TypeError)
  end
end

# Standard Objects
# ---------------------------------------------------------------------------------------------------
#
# ARGF             Object          A synonym for $<.
# ARGV             Array           A synonym for $*.
# ENV              Object          A hash-like object containing the program’s environment variables. An
#                                  instance of class Object, ENV implements the full set of Hash methods. Used
#                                  to query and set the value of an environment variable, as in ENV["PATH"]
#                                  and ENV["term"]="ansi".
# false            FalseClass      Singleton instance of class FalseClass. [r/o]
# nil              NilClass        The singleton instance of class NilClass. The value of uninitialized
#                                  instance and global variables. [r/o]
# self             Object          The receiver (object) of the current method. [r/o]
# true             TrueClass       Singleton instance of class TrueClass. [r/o]

describe "The predefined standard objects" do
  it "includes ARGF" do
    Object.const_defined?(:ARGF).should == true
  end

  it "includes ARGV" do
    Object.const_defined?(:ARGV).should == true
  end

  it "includes a hash-like object ENV" do
    Object.const_defined?(:ENV).should == true
    ENV.respond_to?(:[]).should == true
  end
end

describe "The predefined standard object nil" do
  it "is an instance of NilClass" do
    nil.should be_kind_of(NilClass)
  end

  it "raises a SyntaxError if assigned to" do
    -> { eval("nil = true") }.should raise_error(SyntaxError)
  end
end

describe "The predefined standard object true" do
  it "is an instance of TrueClass" do
    true.should be_kind_of(TrueClass)
  end

  it "raises a SyntaxError if assigned to" do
    -> { eval("true = false") }.should raise_error(SyntaxError)
  end
end

describe "The predefined standard object false" do
  it "is an instance of FalseClass" do
    false.should be_kind_of(FalseClass)
  end

  it "raises a SyntaxError if assigned to" do
    -> { eval("false = nil") }.should raise_error(SyntaxError)
  end
end

describe "The self pseudo-variable" do
  it "raises a SyntaxError if assigned to" do
    -> { eval("self = 1") }.should raise_error(SyntaxError)
  end
end

# Global Constants
# ---------------------------------------------------------------------------------------------------
#
# The following constants are defined by the Ruby interpreter.
#
# DATA                 IO          If the main program file contains the directive __END__, then
#                                  the constant DATA will be initialized so that reading from it will
#                                  return lines following __END__ from the source file.
# FALSE                FalseClass  Synonym for false (deprecated, removed in Ruby 3).
# NIL                  NilClass    Synonym for nil (deprecated, removed in Ruby 3).
# RUBY_PLATFORM        String      The identifier of the platform running this program. This string
#                                  is in the same form as the platform identifier used by the GNU
#                                  configure utility (which is not a coincidence).
# RUBY_RELEASE_DATE    String      The date of this release.
# RUBY_VERSION         String      The version number of the interpreter.
# STDERR               IO          The actual standard error stream for the program. The initial
#                                  value of $stderr.
# STDIN                IO          The actual standard input stream for the program. The initial
#                                  value of $stdin.
# STDOUT               IO          The actual standard output stream for the program. The initial
#                                  value of $stdout.
# SCRIPT_LINES__       Hash        If a constant SCRIPT_LINES__ is defined and references a Hash,
#                                  Ruby will store an entry containing the contents of each file it
#                                  parses, with the file’s name as the key and an array of strings as
#                                  the value.
# TOPLEVEL_BINDING     Binding     A Binding object representing the binding at Ruby’s top level—
#                                  the level where programs are initially executed.
# TRUE                 TrueClass   Synonym for true (deprecated, removed in Ruby 3).

describe "The predefined global constants" do
  describe "TRUE" do
    it "is no longer defined" do
      Object.const_defined?(:TRUE).should == false
    end
  end

  describe "FALSE" do
    it "is no longer defined" do
      Object.const_defined?(:FALSE).should == false
    end
  end

  describe "NIL" do
    it "is no longer defined" do
      Object.const_defined?(:NIL).should == false
    end
  end

  it "includes STDIN" do
    Object.const_defined?(:STDIN).should == true
  end

  it "includes STDOUT" do
    Object.const_defined?(:STDOUT).should == true
  end

  it "includes STDERR" do
    Object.const_defined?(:STDERR).should == true
  end

  it "includes RUBY_VERSION" do
    Object.const_defined?(:RUBY_VERSION).should == true
  end

  it "includes RUBY_RELEASE_DATE" do
    Object.const_defined?(:RUBY_RELEASE_DATE).should == true
  end

  it "includes RUBY_PLATFORM" do
    Object.const_defined?(:RUBY_PLATFORM).should == true
  end

  it "includes TOPLEVEL_BINDING" do
    Object.const_defined?(:TOPLEVEL_BINDING).should == true
  end
end

describe "The predefined global constant" do
  before :each do
    @external = Encoding.default_external
    @internal = Encoding.default_internal
  end

  after :each do
    Encoding.default_external = @external
    Encoding.default_internal = @internal
  end

  describe "STDIN" do
    platform_is_not :windows do
      it "has the same external encoding as Encoding.default_external" do
        STDIN.external_encoding.should equal(Encoding.default_external)
      end

      it "has the same external encoding as Encoding.default_external when that encoding is changed" do
        Encoding.default_external = Encoding::ISO_8859_16
        STDIN.external_encoding.should equal(Encoding::ISO_8859_16)
      end

      it "has nil for the internal encoding" do
        STDIN.internal_encoding.should be_nil
      end

      it "has nil for the internal encoding despite Encoding.default_internal being changed" do
        Encoding.default_internal = Encoding::IBM437
        STDIN.internal_encoding.should be_nil
      end
    end

    it "has the encodings set by #set_encoding" do
      code = "STDIN.set_encoding Encoding::IBM775, Encoding::IBM866; " \
             "p [STDIN.external_encoding.name, STDIN.internal_encoding.name]"
      ruby_exe(code).chomp.should == %{["IBM775", "IBM866"]}
    end

    it "retains the encoding set by #set_encoding when Encoding.default_external is changed" do
      code = "STDIN.set_encoding Encoding::IBM775, Encoding::IBM866; " \
             "Encoding.default_external = Encoding::ISO_8859_16;" \
             "p [STDIN.external_encoding.name, STDIN.internal_encoding.name]"
      ruby_exe(code).chomp.should == %{["IBM775", "IBM866"]}
    end
  end

  describe "STDOUT" do
    it "has nil for the external encoding" do
      STDOUT.external_encoding.should be_nil
    end

    it "has nil for the external encoding despite Encoding.default_external being changed" do
      Encoding.default_external = Encoding::ISO_8859_1
      STDOUT.external_encoding.should be_nil
    end

    it "has the encodings set by #set_encoding" do
      code = "STDOUT.set_encoding Encoding::IBM775, Encoding::IBM866; " \
             "p [STDOUT.external_encoding.name, STDOUT.internal_encoding.name]"
      ruby_exe(code).chomp.should == %{["IBM775", "IBM866"]}
    end

    it "has nil for the internal encoding" do
      STDOUT.internal_encoding.should be_nil
    end

    it "has nil for the internal encoding despite Encoding.default_internal being changed" do
      Encoding.default_internal = Encoding::IBM437
      STDOUT.internal_encoding.should be_nil
    end
  end

  describe "STDERR" do
    it "has nil for the external encoding" do
      STDERR.external_encoding.should be_nil
    end

    it "has nil for the external encoding despite Encoding.default_external being changed" do
      Encoding.default_external = Encoding::ISO_8859_1
      STDERR.external_encoding.should be_nil
    end

    it "has the encodings set by #set_encoding" do
      code = "STDERR.set_encoding Encoding::IBM775, Encoding::IBM866; " \
             "p [STDERR.external_encoding.name, STDERR.internal_encoding.name]"
      ruby_exe(code).chomp.should == %{["IBM775", "IBM866"]}
    end

    it "has nil for the internal encoding" do
      STDERR.internal_encoding.should be_nil
    end

    it "has nil for the internal encoding despite Encoding.default_internal being changed" do
      Encoding.default_internal = Encoding::IBM437
      STDERR.internal_encoding.should be_nil
    end
  end

  describe "ARGV" do
    it "contains Strings encoded in locale Encoding" do
      code = fixture __FILE__, "argv_encoding.rb"
      result = ruby_exe(code, args: "a b")
      encoding = Encoding.default_external
      result.chomp.should == %{["#{encoding}", "#{encoding}"]}
    end
  end
end

describe "$LOAD_PATH.resolve_feature_path" do
  it "returns what will be loaded without actual loading, .rb file" do
    extension, path = $LOAD_PATH.resolve_feature_path('pp')
    extension.should == :rb
    path.should.end_with?('/pp.rb')
  end

  it "returns what will be loaded without actual loading, .so file" do
    require 'rbconfig'
    skip "no dynamically loadable standard extension" if RbConfig::CONFIG["EXTSTATIC"] == "static"

    extension, path = $LOAD_PATH.resolve_feature_path('etc')
    extension.should == :so
    path.should.end_with?("/etc.#{RbConfig::CONFIG['DLEXT']}")
  end

  it "return nil if feature cannot be found" do
    $LOAD_PATH.resolve_feature_path('noop').should be_nil
  end
end

# Some other pre-defined global variables

describe "Predefined global $=" do
  before :each do
    @verbose, $VERBOSE = $VERBOSE, nil
    @dollar_assign = $=
  end

  after :each do
    $= = @dollar_assign
    $VERBOSE = @verbose
  end

  it "warns when accessed" do
    -> { a = $= }.should complain(/is no longer effective/)
  end

  it "warns when assigned" do
    -> { $= = "_" }.should complain(/is no longer effective/)
  end

  it "returns the value assigned" do
    ($= = "xyz").should == "xyz"
  end
end