string.rb

require 'citrus'

Citrus.eval(<<'CODE')
grammar RubyString
  rule string
    single_quoted_string | double_quoted_string
  end

  # This should be expanded to account for escaped single quotes.
  rule single_quoted_string
    "'" (!"'" .)* "'"
  end

  # This should be expanded to account for escaped double quotes.
  rule double_quoted_string
    ('"' (string_interpolation | !'"' .)* '"') {
      def interpolations
        find(:string_interpolation)
      end

      def contains_malformed_interpolation?
        interpolations.any? {|s| s.malformed? }
      end
    }
  end

  rule string_interpolation
    ('#{' ruby_curly_source '}') {
      def malformed?
        !! (ruby_curly_source.text =~ /^\s|\s$/)
      end
    }
  end

  # Ruby source code that may be contained inside curly braces.
  rule ruby_curly_source
    (!'}' (ruby_curly_block | .))*
  end

  rule ruby_curly_block
    '{' ruby_curly_source '}'
  end
end
CODE

if $0 == __FILE__
  require 'test/unit'

  class RubyStringTest < Test::Unit::TestCase
    def test_ruby_curly_block
      m = RubyString.parse('{}', :root => :ruby_curly_block)
      assert(m)

      m = RubyString.parse('{ some_var }', :root => :ruby_curly_block)
      assert(m)

      m = RubyString.parse('{ :a => {} }', :root => :ruby_curly_block)
      assert(m)
    end

    def test_ruby_curly_source
      m = RubyString.parse('some_call', :root => :ruby_curly_source)
      assert(m)

      m = RubyString.parse('some_call_with_a_block {}', :root => :ruby_curly_source)
      assert(m)
    end

    def test_string_interpolation
      m = RubyString.parse('#{}', :root => :string_interpolation)
      assert(m)

      m = RubyString.parse('#{some_var}', :root => :string_interpolation)
      assert(m)
      assert(!m.malformed?)

      m = RubyString.parse('#{ some_var }', :root => :string_interpolation)
      assert(m)
      assert(m.malformed?)

      m = RubyString.parse('#{some_call {}.to_s}', :root => :string_interpolation)
      assert(m)
      assert(!m.malformed?)

      m = RubyString.parse('#{ some_call {}.to_s }', :root => :string_interpolation)
      assert(m)
      assert(m.malformed?)
    end

    def test_single_quoted_string
      m = RubyString.parse("''", :root => :single_quoted_string)
      assert(m)

      m = RubyString.parse("'a'", :root => :single_quoted_string)
      assert(m)
    end

    def test_double_quoted_string
      m = RubyString.parse('""', :root => :double_quoted_string)
      assert(m)

      m = RubyString.parse('"a"', :root => :double_quoted_string)
      assert(m)

      m = RubyString.parse('"a #{some_var} string"', :root => :double_quoted_string)
      assert(m)
      assert(!m.contains_malformed_interpolation?)

      m = RubyString.parse('"a #{ some_var} string"', :root => :double_quoted_string)
      assert(m)
      assert(m.contains_malformed_interpolation?)
    end
  end
end