Adding support for providing a diff when files are being changed. Currently uses a local diff binary, but could easily be changed to use the ruby diff/lcs library. Modified puppet and puppetd to automatically show file diffs when in noop mode, but can otherwise be enabled using --show_diff. This only works when running interactively, because the diffs are printed on stdout.

1 files changed, 71 insertions, 0 deletions

diff --git a/lib/puppet/util/diff.rb b/lib/puppet/util/diff.rb
new file mode 100644
index 000000000..e6ff57108
--- /dev/null
+++ b/lib/puppet/util/diff.rb
@@ -0,0 +1,71 @@
+# Provide a diff between two strings.
+module Puppet::Util::Diff
+    include Puppet::Util
+    require 'tempfile'
+
+    def diff(old, new)
+        command = [Puppet[:diff]]
+        if args = Puppet[:diff_args] and args != ""
+            command << args
+        end
+        command << old << new
+        execute(command, :failonfail => false)
+    end
+
+    module_function :diff
+
+    # return diff string of two input strings
+    # format defaults to unified
+    # context defaults to 3 lines
+    def lcs_diff(data_old, data_new, format=:unified, context_lines=3)
+        unless Puppet.features.diff?
+            Puppet.warning "Cannot provide diff without the diff/lcs Ruby library"
+            return ""
+        end
+        data_old = data_old.split(/\n/).map! { |e| e.chomp }
+        data_new = data_new.split(/\n/).map! { |e| e.chomp }
+
+        output = ""
+
+        diffs = Diff::LCS.diff(data_old, data_new)
+        return output if diffs.empty?
+
+        oldhunk = hunk = nil
+        file_length_difference = 0
+
+        diffs.each do |piece|
+            begin
+                hunk = Diff::LCS::Hunk.new(data_old, data_new, piece, 
+                                           context_lines, 
+                                           file_length_difference)
+                file_length_difference = hunk.file_length_difference
+            next unless oldhunk
+            # Hunks may overlap, which is why we need to be careful when our
+            # diff includes lines of context. Otherwise, we might print
+            # redundant lines.
+            if (context_lines > 0) and hunk.overlaps?(oldhunk)
+                hunk.unshift(oldhunk)
+            else
+                output << oldhunk.diff(format)
+            end
+            ensure
+                oldhunk = hunk
+                output << "\n"
+            end
+        end
+
+        # Handle the last remaining hunk
+        output << oldhunk.diff(format) << "\n"
+    end
+
+    def string_file_diff(path, string)
+        require 'tempfile'
+        tempfile = Tempfile.new("puppet-diffing")
+        tempfile.open
+        tempfile.print string
+        tempfile.close
+        print diff(path, tempfile.path)
+        tempfile.delete
+    end
+end
+