Diffy - Easy Diffing With Ruby

Need diffs in your ruby app? Diffy has you covered. It provides a convenient way to generate a diff from two strings or files. Instead of reimplementing the LCS diff algorithm Diffy uses battle tested Unix diff to generate diffs, and focuses on providing a convenient interface, and getting out of your way.

Supported Formats

It provides several built in format options which can be passed to Diffy::Diff#to_s.

:text - Plain text output
:color - ANSI colorized text suitable for use in a terminal
:html - HTML output. Since version 2.0 this format does inline highlighting of the character changes between lines.
:html_simple - HTML output without inline highlighting. This may be useful in situations where high performance is required or simpler output is desired.

A default format can be set like so:

Diffy::Diff.default_format = :html

Installation

###on Unix

gem install diffy

###on Windows:

Ensure that you have a working diff on your machine and in your search path.

There are several options:
1. Install Diff::LCS, which includes ldiff. RSpec depends on Diff::LCS so you may already have it installed.
2. If you're using RubyInstaller, install the devkit.
3. Install unxutils http://sourceforge.net/projects/unxutils
  
  note that these tools contain diff 2.7 which has a different handling of whitespace in the diff results. This makes Diffy spec tests yielding one fail on Windows.
4. Install these two individually from the gnuwin32 project http://gnuwin32.sourceforge.net/
  
  note that this delivers diff 2.8 which makes Diffy spec pass even on Windows.
Install the gem by
```
gem install diffy
```

Getting Started

Here's an example of using Diffy to diff two strings

$ irb
>> string1 = <<-TXT
>" Hello how are you
>" I'm fine
>" That's great
>" TXT
=> "Hello how are you\nI'm fine\nThat's great\n"
>> string2 = <<-TXT
>" Hello how are you?
>" I'm fine
>" That's swell
>" TXT
=> "Hello how are you?\nI'm fine\nThat's swell\n"
>> puts Diffy::Diff.new(string1, string2)
-Hello how are you
+Hello how are you?
 I'm fine
-That's great
+That's swell

HTML Output

Outputing the diff as html is easy too. Here's an example using the :html_simple formatter.

>> puts Diffy::Diff.new(string1, string2).to_s(:html_simple)
<div class="diff">
  <ul>
    <li class="del"><del>Hello how are you</del></li>
    <li class="ins"><ins>Hello how are you?</ins></li>
    <li class="unchanged"><span>I'm fine</span></li>
    <li class="del"><del>That's great</del></li>
    <li class="ins"><ins>That's swell</ins></li>
  </ul>
</div>

The :html formatter will give you inline highlighting a la github.

>> puts Diffy::Diff.new("foo\n", "Foo\n").to_s(:html)
<div class="diff">
  <ul>
    <li class="del"><del><strong>f</strong>oo</del></li>
    <li class="ins"><ins><strong>F</strong>oo</ins></li>
  </ul>
</div>

There's some pretty nice css provided in Diffy::CSS.

>> puts Diffy::CSS
.diff{overflow:auto;}
.diff ul{background:#fff;overflow:auto;font-size:13px;list-style:none;margin:0;padding:0;display:table;width:100%;}
.diff del, .diff ins{display:block;text-decoration:none;}
.diff li{padding:0; display:table-row;margin: 0;height:1em;}
.diff li.ins{background:#dfd; color:#080}
.diff li.del{background:#fee; color:#b00}
.diff li:hover{background:#ffc}
/* try 'whitespace:pre;' if you don't want lines to wrap */
.diff del, .diff ins, .diff span{white-space:pre-wrap;font-family:courier;}
.diff del strong{font-weight:normal;background:#fcc;}
.diff ins strong{font-weight:normal;background:#9f9;}
.diff li.diff-comment { display: none; }
.diff li.diff-block-info { background: none repeat scroll 0 0 gray; }

There's also a colorblind-safe version of the pallete provided in Diffy::CSS_COLORBLIND_1.

Other Diff Options

Diffing files instead of strings

You can diff files instead of strings by using the :source option.

>> puts Diffy::Diff.new('/tmp/foo', '/tmp/bar', :source => 'files')

Full Diff Output

By default Diffy removes the superfluous diff output. This is because its default is to show the complete diff'ed file (diff -U 10000 is the default).

Diffy does support full output, just use the :include_diff_info => true option when initializing:

>> Diffy::Diff.new("foo\nbar\n", "foo\nbar\nbaz\n", :include_diff_info => true).to_s(:text)
=>--- /Users/chaffeqa/Projects/stiwiki/tmp/diffy20111116-82153-ie27ex	2011-11-16 20:16:41.000000000 -0500
+++ /Users/chaffeqa/Projects/stiwiki/tmp/diffy20111116-82153-wzrhw5	2011-11-16 20:16:41.000000000 -0500
@@ -1,2 +1,3 @@
 foo
 bar
+baz

And even deals a bit with the formatting!

Empty Diff Behavior

By default Diffy will return empty string if there are no differences in inputs. In previous versions the full text of its first input was returned in this case. To restore this behaviour simply use the :allow_empty_diff => false option when initializing.

Plus and Minus symbols in HTML output

By default Diffy doesn't include the +, -, and at the beginning of line for HTML output.

You can use the :include_plus_and_minus_in_html option to include those symbols in the output.

>> puts Diffy::Diff.new(string1, string2, :include_plus_and_minus_in_html => true).to_s(:html_simple)
<div class="diff">
  <ul>
    <li class="del"><del><span class="symbol">-</span>Hello how are you</del></li>
    <li class="ins"><ins><span class="symbol">+</span>Hello how are you?</ins></li>
    <li class="unchanged"><span class="symbol"> </span><span>I'm fine</span></li>
    <li class="del"><del><span class="symbol">-</span>That's great</del></li>
    <li class="ins"><ins><span class="symbol">+</span>That's swell</ins></li>
  </ul>
</div>

Number of lines of context around changes

You can use the :context option to override the number of lines of context that are shown around each change (this defaults to 10000 to show the full file).

>> puts Diffy::Diff.new("foo\nfoo\nBAR\nbang\nbaz", "foo\nfoo\nbar\nbang\nbaz", :context => 1)
 foo
-BAR
+bar
 bang

Overriding the command line options passed to diff.

You can use the :diff option to override the command line options that are passed to unix diff. They default to -U 10000. This option will noop if combined with the :context option.

>> puts Diffy::Diff.new(" foo\nbar\n", "foo\nbar\n", :diff => "-w")
  foo
 bar

Default Diff Options

You can set the default options for new Diffy::Diffs using the Diffy::Diff.default_options and Diffy::Diff.default_options= methods. Options passed to Diffy::Diff.new will be merged into the default options.

>> Diffy::Diff.default_options
=> {:diff=>"-U 10000", :source=>"strings", :include_diff_info=>false, :include_plus_and_minus_in_html=>false}
>> Diffy::Diff.default_options.merge!(:source => 'files')
=> {:diff=>"-U 10000", :source=>"files", :include_diff_info=>false, :include_plus_and_minus_in_html=>false}

Custom Formats

Diffy tries to make generating your own custom formatted output easy. Diffy::Diff provides an enumerable interface which lets you iterate over lines in the diff.

>> Diffy::Diff.new("foo\nbar\n", "foo\nbar\nbaz\n").each do |line|
>*   case line
>>   when /^\+/ then puts "line #{line.chomp} added"
>>   when /^-/ then puts "line #{line.chomp} removed"
>>   end
>> end
line +baz added
=> [" foo\n", " bar\n", "+baz\n"]

You can also use Diffy::Diff#each_chunk to iterate each grouping of additions, deletions, and unchanged in a diff.

>> Diffy::Diff.new("foo\nbar\nbang\nbaz\n", "foo\nbar\nbing\nbong\n").each_chunk.to_a
=> [" foo\n bar\n", "-bang\n-baz\n", "+bing\n+bong\n"]

Use #map, #inject, or any of Enumerable's methods. Go crazy.

Ruby Version Compatibility

Support for Ruby 1.8.6 was dropped beginning at version 2.0 in order to support the chainable enumerators available in 1.8.7 and 1.9.

If you want to use Diffy and Ruby 1.8.6 then:

$ gem install diffy -v1.1.0

Testing

Diffy includes a full set of rspec tests. When contributing please include tests for your changes.

Report bugs or request features at http://github.com/samg/diffy/issues

looker / diffy