Updates from review feedback

Author: dmsnell

java/src/name/fraser/neil/plaintext/diff_match_patch.java

@@ -1447,6 +1447,9 @@ public String diff_toDelta(List<Diff> diffs) {
 
       isFirst = false;
       lastEnd = thisEnd;
+      if ( aDiff.text.isEmpty() ) {
+        continue;
+      }
 
       switch (aDiff.operation) {
       case INSERT:

javascript/diff_match_patch_uncompressed.js

@@ -1375,6 +1375,9 @@ diff_match_patch.prototype.diff_toDelta = function(diffs) {
     }
 
     lastEnd = thisEnd;
+    if ( 0 === thisDiff[1].length ) {
+      continue;
+    }
 
     switch (diffs[x][0]) {
       case DIFF_INSERT:

objectivec/DiffMatchPatch.m

@@ -1299,7 +1299,7 @@ - (NSString *)diff_text2:(NSMutableArray *)diffs;
 - (NSString *)diff_toDelta:(NSMutableArray *)diffs;
 {
   NSMutableString *delta = [NSMutableString string];
-  UniChar lastEnd;
+  UniChar lastEnd = 0;
   for (Diff *aDiff in diffs) {
 
     UniChar thisTop = [aDiff.text characterAtIndex:0];
@@ -1309,11 +1309,14 @@ - (NSString *)diff_toDelta:(NSMutableArray *)diffs;
       aDiff.text = [aDiff.text substringToIndex:([aDiff.text length] - 1)];
     }
 
-    if (nil != lastEnd && CFStringIsSurrogateHighCharacter(lastEnd) && CFStringIsSurrogateLowCharacter(thisTop)) {
-      aDiff.text = [[NSString stringWithFormat:@"%C", lastEnd] stringByAppendingString:aDiff.text];
+    if (0 != lastEnd && CFStringIsSurrogateHighCharacter(lastEnd) && CFStringIsSurrogateLowCharacter(thisTop)) {
+      aDiff.text = [NSString stringWithFormat:@"%C%@", lastEnd, stringByAppendingString:aDiff.text];
     }
 
     lastEnd = thisEnd;
+    if (0 == [aDiff.text length]) {
+      continue;
+    }
 
     switch (aDiff.operation) {
       case DIFF_INSERT:

objectivec/Tests/DiffMatchPatchTest.m

@@ -752,6 +752,18 @@ - (void)test_diff_deltaTest {
 
   XCTAssertEqualObjects(diffs, [dmp diff_fromDeltaWithText:text1 andDelta:delta error:NULL], @"diff_fromDelta: Unicode 2.");
 
+  diffs = [dmp diff_mainOfOldString:@"☺️🖖🏿" andNewString:@"☺️😃🖖🏿"];
+  delta = [dmp diff_toDelta:diffs];
+
+  XCTAssertEqualObjects(delta, @"=2\t+%F0%9F%98%83\t=4", @"Delta should match the expected string");
+
+  diffs = [dmp diff_mainOfOldString:@"☺️🖖🏿" andNewString:@"☺️😃🖖🏿"];
+  patches = [dmp patch_makeFromDiffs:diffs];
+  expectedResult = [dmp patch_apply:patches toString:@"☺️🖖🏿"];
+
+  expectedString = [result firstObject];
+  XCTAssertEqualObjects(edited, expectedString, @"Output String should match the Edited one!");
+
   // Verify pool of unchanged characters.
   diffs = [NSMutableArray arrayWithObject:
        [Diff diffWithOperation:DIFF_INSERT andText:@"A-Z a-z 0-9 - _ . ! ~ * ' ( ) ; / ? : @ & = + $ , # "]];

python2/diff_match_patch.py

@@ -1173,6 +1173,8 @@ def diff_toDelta(self, diffs):
 
       data = encoded.decode('utf-16be')
       last_end = this_end
+      if 0 == len(encoded):
+        continue
 
       if op == self.DIFF_INSERT:
         # High ascii will raise UnicodeDecodeError.  Use Unicode instead.

python3/diff_match_patch.py

@@ -1147,7 +1147,6 @@ def diff_toDelta(self, diffs):
       Delta text.
     """
     text = []
-    last_end = None
     for (op, data) in diffs:
       if op == self.DIFF_INSERT:
         # High ascii will raise UnicodeDecodeError.  Use Unicode instead.