spec/ruby/core/basicobject/instance_exec_spec.rb


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require_relative '../../spec_helper'
require_relative 'fixtures/classes'

describe "BasicObject#instance_exec" do
  it "is a public instance method" do
    BasicObject.should have_public_instance_method(:instance_exec)
  end

  it "sets self to the receiver in the context of the passed block" do
    a = BasicObject.new
    a.instance_exec { self }.equal?(a).should be_true
  end

  it "passes arguments to the block" do
    a = BasicObject.new
    a.instance_exec(1) { |b| b }.should equal(1)
  end

  it "raises a LocalJumpError unless given a block" do
    -> { "hola".instance_exec }.should raise_error(LocalJumpError)
  end

  it "has an arity of -1" do
    Object.new.method(:instance_exec).arity.should == -1
  end

  it "accepts arguments with a block" do
    -> { "hola".instance_exec(4, 5) { |a,b| a + b } }.should_not raise_error
  end

  it "doesn't pass self to the block as an argument" do
    "hola".instance_exec { |o| o }.should be_nil
  end

  it "passes any arguments to the block" do
    Object.new.instance_exec(1,2) {|one, two| one + two}.should == 3
  end

  it "only binds the exec to the receiver" do
    f = Object.new
    f.instance_exec do
      def foo
        1
      end
    end
    f.foo.should == 1
    -> { Object.new.foo }.should raise_error(NoMethodError)
  end

  # TODO: This should probably be replaced with a "should behave like" that uses
  # the many scoping/binding specs from kernel/eval_spec, since most of those
  # behaviors are the same for instance_exec. See also module_eval/class_eval.

  it "binds self to the receiver" do
    s = "hola"
    (s == s.instance_exec { self }).should == true
  end

  it "binds the block's binding self to the receiver" do
    s = "hola"
    (s == s.instance_exec { eval "self", binding }).should == true
  end

  it "executes in the context of the receiver" do
    "Ruby-fu".instance_exec { size }.should == 7
    Object.class_eval { "Ruby-fu".instance_exec{ to_s } }.should == "Ruby-fu"
  end

  it "has access to receiver's instance variables" do
    BasicObjectSpecs::IVars.new.instance_exec { @secret }.should == 99
  end

  it "sets class variables in the receiver" do
    BasicObjectSpecs::InstExec.class_variables.should include(:@@count)
    BasicObjectSpecs::InstExec.send(:class_variable_get, :@@count).should == 2
  end

  it "raises a TypeError when defining methods on an immediate" do
    -> do
      1.instance_exec { def foo; end }
    end.should raise_error(TypeError)
    -> do
      :foo.instance_exec { def foo; end }
    end.should raise_error(TypeError)
  end

quarantine! do # Not clean, leaves cvars lying around to break other specs
  it "scopes class var accesses in the caller when called on a Fixnum" do
    # Fixnum can take instance vars
    Fixnum.class_eval "@@__tmp_instance_exec_spec = 1"
    (defined? @@__tmp_instance_exec_spec).should == nil

    @@__tmp_instance_exec_spec = 2
    1.instance_exec { @@__tmp_instance_exec_spec }.should == 2
    Fixnum.__send__(:remove_class_variable, :@@__tmp_instance_exec_spec)
  end
end

  it "raises a TypeError when defining methods on numerics" do
    -> do
      (1.0).instance_exec { def foo; end }
    end.should raise_error(TypeError)
    -> do
      (1 << 64).instance_exec { def foo; end }
    end.should raise_error(TypeError)
  end
end