Remove diff edge case special cases

These should still fail quickly and by not short circuiting this we can include information like the token count in the response.

Fixes #69

Author: kpdecker

src/diff/base.js

@@ -19,19 +19,8 @@ Diff.prototype = {
     oldString = this.castInput(oldString);
     newString = this.castInput(newString);
 
-    // Handle the identity case (this is due to unrolling editLength == 0
-    if (newString === oldString) {
-      return done([{ value: newString }]);
-    }
-    if (!newString) {
-      return done([{ value: oldString, removed: true }]);
-    }
-    if (!oldString) {
-      return done([{ value: newString, added: true }]);
-    }
-
-    newString = this.removeEmpty(this.tokenize(newString));
     oldString = this.removeEmpty(this.tokenize(oldString));
+    newString = this.removeEmpty(this.tokenize(newString));
 
     let newLen = newString.length, oldLen = oldString.length;
     let editLength = 1;
@@ -42,7 +31,7 @@ Diff.prototype = {
     let oldPos = this.extractCommon(bestPath[0], newString, oldString, 0);
     if (bestPath[0].newPos + 1 >= newLen && oldPos + 1 >= oldLen) {
       // Identity per the equality and tokenizer
-      return done([{value: newString.join('')}]);
+      return done([{value: newString.join(''), count: newString.length}]);
     }
 
     // Main worker method. checks all permutations of a given edit length for acceptance.

test/diff/word.js

@@ -65,6 +65,18 @@ describe('WordDiff', function() {
       expect(wordDiff.removeEmpty(wordDiff.tokenize('jurídica'))).to.eql(['jurídica']);
       expect(wordDiff.removeEmpty(wordDiff.tokenize('wir üben'))).to.eql(['wir', ' ', 'üben']);
     });
+
+    it('should include count with identity cases', function() {
+      expect(diffWords('foo', 'foo')).to.eql([{value: 'foo', count: 1}]);
+      expect(diffWords('foo bar', 'foo bar')).to.eql([{value: 'foo bar', count: 3}]);
+    });
+    it('should include count with empty cases', function() {
+      expect(diffWords('foo', '')).to.eql([{value: 'foo', count: 1, added: undefined, removed: true}]);
+      expect(diffWords('foo bar', '')).to.eql([{value: 'foo bar', count: 3, added: undefined, removed: true}]);
+
+      expect(diffWords('', 'foo')).to.eql([{value: 'foo', count: 1, added: true, removed: undefined}]);
+      expect(diffWords('', 'foo bar')).to.eql([{value: 'foo bar', count: 3, added: true, removed: undefined}]);
+    });
   });
 
   describe('#diffWords - async', function() {