When a merge fails, queue the object to be synced again (#203)

* When a merge fails, queue the object to be synced again

* Throw a JSONException if diff match patch didn't apply the patches correctly.

* Don't update the object when we encounter an error merging local modifications.

* Revert "When a merge fails, queue the object to be synced again"

This reverts commit 1b83001.

* Adding test for invalid transform exception.

Author: beaucollins

Simperium/src/androidTestSupport/java/com/simperium/JSONDiffTest.java

@@ -338,6 +338,24 @@ public void testTransformStringDiff()
 
     }
 
+    public void testInvalidStringTransformThrowsException()
+            throws Exception {
+        String origin = "Line 1\nLine 2\nReplace me";
+        try
+        {
+            JSONObject transformed = JSONDiff.transform(
+                    "=14\t+Before%0A\t=10\t+%0AAfter",
+                    "=14\t-10\t+BYE",
+                    origin
+            );
+            fail("Patch transform should have failed.");
+        }
+        catch(Exception e)
+        {
+            // Test passed
+        }
+    }
+
     public void testTransformObjectDiffChangeRemovedKey()
     throws Exception {
 

Simperium/src/main/java/com/simperium/client/Bucket.java

@@ -927,6 +927,7 @@ public Ghost applyRemoteChange(RemoteChange change)
             try {
                 T object;
                 Boolean isNew;
+                Boolean shouldUpdateObject = true;
 
                 if (change.isAddOperation()) {
                     object = newObject(change.getKey());
@@ -962,7 +963,6 @@ public Ghost applyRemoteChange(RemoteChange change)
                     mSchema.updateWithDefaults(object, updatedProperties);
                     addObject(object);
                 } else {
-
                     if (localModifications != null && localModifications.length() > 0) {
                         try {
                             JSONObject incomingDiff = change.getPatch();
@@ -971,15 +971,17 @@ public Ghost applyRemoteChange(RemoteChange change)
                             JSONObject transformedDiff = JSONDiff.transform(localDiff, incomingDiff, currentProperties);
 
                             updatedProperties = JSONDiff.apply(updatedProperties, transformedDiff);
-
                         } catch (JSONException | IllegalArgumentException e) {
-                            // could not transform properties
-                            // continue with updated properties
+                            // We couldn't merge the local and remote changes.
+                            // Hold off on updating the object so that the local change can sync
+                            shouldUpdateObject = false;
                         }
                     }
 
-                    mSchema.update(object, updatedProperties);
-                    updateObject(object);
+                    if (shouldUpdateObject) {
+                        mSchema.update(object, updatedProperties);
+                        updateObject(object);
+                    }
                 }
 
             } catch(SimperiumException e) {

Simperium/src/main/java/com/simperium/util/JSONDiff.java

@@ -43,8 +43,16 @@ public static JSONObject transform(String o_diff, String diff, String source)
         LinkedList<Patch> patches = dmp.patch_make(source, dmp.diff_fromDelta(source, diff));
 
         String text = (String) dmp.patch_apply(patches, source)[0];
-        String combined = (String) dmp.patch_apply(o_patches, text)[0];
 
+        Object[] appliedPatch = dmp.patch_apply(o_patches, text);
+        boolean[] results = (boolean[]) appliedPatch[1];
+        for (boolean result : results) {
+            if (!result) {
+                throw new JSONException("Could not cleanly transform patch.");
+            }
+        }
+
+        String combined = (String)appliedPatch[0];
         if (text.equals(combined)) {
             // text is the same, return empty diff
             return transformed;