Reintroduce Diff::LCS::Change#to_ary

-   This required some level of code remediation in the main library, but all
    tests now pass:

    -  Patchsets are now internally flattened one level explicitly, rather than
       using Array#flatten. This ensures that only the outer patchset array is
       flattened.

Fixes #48.

3 files changed, 32 insertions, 14 deletions

diff --git a/lib/diff/lcs.rb b/lib/diff/lcs.rb
index d3a75fd..f33a452 100644
--- a/lib/diff/lcs.rb
+++ b/lib/diff/lcs.rb
@@ -50,7 +50,7 @@ module Diff; end unless defined? Diff # rubocop:disable Style/Documentation
 #          a x b y c z p d q
 #    a b c a x b y c z
 module Diff::LCS
-  VERSION = '1.3'
+  VERSION = '1.4'
 end
 
 require 'diff/lcs/callbacks'
@@ -181,6 +181,20 @@ class << Diff::LCS
   # Class argument is provided for +callbacks+, #diff will attempt to
   # initialise it. If the +callbacks+ object (possibly initialised) responds
   # to #finish, it will be called.
+  #
+  # Each element of a returned array is a Diff::LCS::ContextChange object,
+  # which can be implicitly converted to an array.
+  #
+  #   Diff::LCS.sdiff(a, b).each do |action, (old_pos, old_element), (new_pos, new_element)|
+  #     case action
+  #     when '!'
+  #       # replace
+  #     when '-'
+  #       # delete
+  #     when '+'
+  #       # insert
+  #     end
+  #   end
   def sdiff(seq1, seq2, callbacks = nil, &block) #:yields diff changes:
     diff_traversal(:sdiff, seq1, seq2, callbacks || Diff::LCS::SDiffCallbacks, &block)
   end
@@ -623,7 +637,7 @@ class << Diff::LCS
 
     patch_map = PATCH_MAP[direction]
 
-    patchset.flatten.each do |change|
+    patchset.each do |change|
       # Both Change and ContextChange support #action
       action = patch_map[change.action]
 
diff --git a/lib/diff/lcs/change.rb b/lib/diff/lcs/change.rb
index 75e1f84..76faf83 100644
--- a/lib/diff/lcs/change.rb
+++ b/lib/diff/lcs/change.rb
@@ -39,6 +39,8 @@ class Diff::LCS::Change
     [@action, @position, @element]
   end
 
+  alias to_ary to_a
+
   def self.from_a(arr)
     arr = arr.flatten(1)
     case arr.size
@@ -125,6 +127,8 @@ class Diff::LCS::ContextChange < Diff::LCS::Change
     ]
   end
 
+  alias to_ary to_a
+
   def self.from_a(arr)
     Diff::LCS::Change.from_a(arr)
   end
diff --git a/lib/diff/lcs/internals.rb b/lib/diff/lcs/internals.rb
index c3360d5..60027f2 100644
--- a/lib/diff/lcs/internals.rb
+++ b/lib/diff/lcs/internals.rb
@@ -91,14 +91,15 @@ class << Diff::LCS::Internals
     vector
   end
 
-  # This method will analyze the provided patchset to provide a
-  # single-pass normalization (conversion of the array form of
-  # Diff::LCS::Change objects to the object form of same) and detection of
-  # whether the patchset represents changes to be made.
+  # This method will analyze the provided patchset to provide a single-pass
+  # normalization (conversion of the array form of Diff::LCS::Change objects to
+  # the object form of same) and detection of whether the patchset represents
+  # changes to be made.
   def analyze_patchset(patchset, depth = 0)
     fail 'Patchset too complex' if depth > 1
 
     has_changes = false
+    new_patchset = []
 
     # Format:
     # [ # patchset
@@ -108,29 +109,28 @@ class << Diff::LCS::Internals
     #   ]
     # ]
 
-    patchset = patchset.map { |hunk|
+    patchset.each do |hunk|
       case hunk
       when Diff::LCS::Change
         has_changes ||= !hunk.unchanged?
-        hunk
+        new_patchset << hunk
       when Array
-        # Detect if the 'hunk' is actually an array-format
-        # Change object.
+        # Detect if the 'hunk' is actually an array-format change object.
         if Diff::LCS::Change.valid_action? hunk[0]
           hunk = Diff::LCS::Change.from_a(hunk)
           has_changes ||= !hunk.unchanged?
-          hunk
+          new_patchset << hunk
         else
           with_changes, hunk = analyze_patchset(hunk, depth + 1)
           has_changes ||= with_changes
-          hunk.flatten
+          new_patchset.concat(hunk)
         end
       else
         fail ArgumentError, "Cannot normalise a hunk of class #{hunk.class}."
       end
-    }
+    end
 
-    [has_changes, patchset.flatten(1)]
+    [has_changes, new_patchset]
   end
 
   # Examine the patchset and the source to see in which direction the