Merge pull request #162 from MrJoy/fix_file_rewriting_with_rewriters

`ruby-rewrite` fails to actually rewrite the input file when a rewriter is loaded.  This fixes the issue.

lib/parser/runner/ruby_rewrite.rb

@@ -43,6 +43,7 @@ def load_and_discover(file)
 
     def process(initial_buffer)
       buffer = initial_buffer
+      original_name = buffer.name
 
       @rewriters.each do |rewriter_class|
         @parser.reset
@@ -81,8 +82,8 @@ def process(initial_buffer)
         buffer = new_buffer
       end
 
-      if File.exist?(buffer.name)
-        File.open(buffer.name, 'w') do |file|
+      if File.exist?(original_name)
+        File.open(original_name, 'w') do |file|
           file.write buffer.source
         end
       else

test/bug_163/fixtures/input.rb

@@ -0,0 +1,3 @@
+if(true)
+  puts "Hello, world!"
+end

test/bug_163/fixtures/output.rb

@@ -0,0 +1,3 @@
+if true
+  puts "Hello, world!"
+end

test/bug_163/rewriter.rb

@@ -0,0 +1,18 @@
+class Rewriter < Parser::Rewriter
+  def on_if(node)
+    # Crude, totally-not-usable-in-the-real-world code to remove optional
+    # parens from control keywords.
+    #
+    # In a perfect test scenario we'd simply make this a no-op, to demonstrate
+    # that the bug happens when any rewriter is loaded regardless of whether it
+    # actually changes anything but that makes assertions much harder to get
+    # right.  It's much easier to just show that the file did, or did not
+    # get changed.
+    if node.children[0].type == :begin
+      replace node.children[0].loc.begin, ' '
+      remove node.children[0].loc.end
+    end
+
+    super
+  end
+end

test/bug_163/test_runner_rewrite.rb

@@ -0,0 +1,35 @@
+require 'pathname'
+require 'fileutils'
+require 'shellwords'
+
+BASE_DIR = Pathname.new(__FILE__) + '../..'
+require (BASE_DIR + 'helper').expand_path
+
+class TestRunnerRewrite < Minitest::Test
+  def setup
+    @ruby_rewrite = BASE_DIR.expand_path + '../bin/ruby-rewrite'
+    @test_dir     = BASE_DIR + 'bug_163'
+    @fixtures_dir = @test_dir + 'fixtures'
+  end
+
+  def test_rewriter
+    Dir.mktmpdir(nil, BASE_DIR.expand_path.to_s) do |tmp_dir|
+      tmp_dir = Pathname.new(tmp_dir)
+      sample_file = tmp_dir + 'bug_163.rb'
+      sample_file_expanded = sample_file.expand_path
+      expected_file = @fixtures_dir + 'output.rb'
+
+      FileUtils.cp(@fixtures_dir + 'input.rb', tmp_dir + 'bug_163.rb')
+      FileUtils.cd @test_dir do
+        exit_code = system %Q{
+          #{Shellwords.escape(@ruby_rewrite.to_s)} --modify \
+            -l rewriter.rb \
+            #{Shellwords.escape(sample_file_expanded.to_s)}
+        }
+      end
+
+      assert File.read(expected_file.expand_path) == File.read(sample_file),
+        "#{sample_file} should be identical to #{expected_file}"
+    end
+  end
+end

test/helper.rb

@@ -1,4 +1,5 @@
 require 'tempfile'
+require 'minitest/test'
 
 require 'simplecov'
 require 'coveralls'