throw_spec.rb

require_relative '../spec_helper'

describe "The throw keyword" do
  it "abandons processing" do
    i = 0
    catch(:done) do
      loop do
        i += 1
        throw :done if i > 4
      end
      i += 1
    end
    i.should == 5
  end

  it "supports a second parameter" do
    msg = catch(:exit) do
      throw :exit,:msg
    end
    msg.should == :msg
  end

  it "uses nil as a default second parameter" do
    msg = catch(:exit) do
      throw :exit
    end
    msg.should == nil
  end

  it "clears the current exception" do
    catch :exit do
      begin
        raise "exception"
      rescue
        throw :exit
      end
    end
    $!.should be_nil
  end

  it "allows any object as its argument" do
    catch(1) { throw 1, 2 }.should == 2
    o = Object.new
    catch(o) { throw o, o }.should == o
  end

  it "does not convert strings to a symbol" do
    -> { catch(:exit) { throw "exit" } }.should raise_error(ArgumentError)
  end

  it "unwinds stack from within a method" do
    def throw_method(handler, val)
      throw handler, val
    end

    catch(:exit) do
      throw_method(:exit, 5)
    end.should == 5
  end

  it "unwinds stack from within a lambda" do
    c = -> { throw :foo, :msg }
    catch(:foo) { c.call }.should == :msg
  end

  it "raises an ArgumentError if outside of scope of a matching catch" do
    -> { throw :test, 5 }.should raise_error(ArgumentError)
    -> { catch(:different) { throw :test, 5 } }.should raise_error(ArgumentError)
  end

  it "raises an UncaughtThrowError if used to exit a thread" do
    catch(:what) do
      t = Thread.new {
        -> {
          throw :what
        }.should raise_error(UncaughtThrowError)
      }
      t.join
    end
  end
end