[fix] Fix non-deterministic move conflict detection, fix #101

Author: slarse

src/main/java/se/kth/spork/base3dm/ChangeSet.java

@@ -2,6 +2,7 @@
 
 import java.util.*;
 import java.util.function.Function;
+import java.util.stream.Collectors;
 import java.util.stream.Stream;
 
 /**
@@ -60,34 +61,34 @@ public Map<T, Set<Content<T,V>>> getContents() {
 
     /**
      * @param pcs A PCS triple.
-     * @return Another PCS that matches the argument PCS on everything but root.
+     * @return All PCSes that are root conflicting with the provided PCS.
      */
-    public Optional<Pcs<T>> getOtherRoot(Pcs<T> pcs) {
+    public List<Pcs<T>> getOtherRoots(Pcs<T> pcs) {
         return Stream.of(pcs.getPredecessor(), pcs.getSuccessor()).flatMap(
                 node -> Stream.of(predecessors.get(node), successors.get(node))
                         .filter(Objects::nonNull)
                         .flatMap(Set::stream)
-        ).filter(p -> !p.getRoot().equals(pcs.getRoot())).findFirst();
+        ).filter(p -> !p.getRoot().equals(pcs.getRoot())).collect(Collectors.toList());
     }
 
     /**
      * @param pcs A PCS triple.
-     * @return Another PCS that matches the argument PCS on everything but successor.
+     * @return All PCSes that are successor conflicting with the provided PCS.
      */
-    public Optional<Pcs<T>> getOtherSuccessor(Pcs<T> pcs) {
+    public List<Pcs<T>> getOtherSuccessors(Pcs<T> pcs) {
         return predecessors.getOrDefault(pcs.getPredecessor(), EMPTY_PCS_SET).stream()
                 .filter(p -> !p.getSuccessor().equals(pcs.getSuccessor()))
-                .findFirst();
+                .collect(Collectors.toList());
     }
 
     /**
      * @param pcs A PCS triple.
-     * @return Another PCS that matches the argument PCS on everything but predecessor.
+     * @return All PCSes that are predecessor conflicting with the provided PCS.
      */
-    public Optional<Pcs<T>> getOtherPredecessor(Pcs<T> pcs) {
+    public List<Pcs<T>> getOtherPredecessors(Pcs<T> pcs) {
         return successors.getOrDefault(pcs.getSuccessor(), EMPTY_PCS_SET).stream()
                 .filter(p -> !p.getPredecessor().equals(pcs.getPredecessor()))
-                .findFirst();
+                .collect(Collectors.toList());
     }
 
     /**

src/main/java/se/kth/spork/base3dm/TdmMerge.java

@@ -39,15 +39,13 @@ public static <T extends ListNode,V> void resolveRawMerge(ChangeSet<T,V> base, C
             mergeContent(pcs.getPredecessor(), base, delta);
             mergeContent(pcs.getSuccessor(), base, delta);
 
-            Optional<Pcs<T>> other = delta.getOtherRoot(pcs);
-            if (!other.isPresent())
-                other = delta.getOtherPredecessor(pcs);
-            if (!other.isPresent())
-                other = delta.getOtherSuccessor(pcs);
-
-            if (other.isPresent()) {
-                Pcs<T> otherPcs = other.get();
+            List<Pcs<T>> others = delta.getOtherRoots(pcs);
+            if (others.isEmpty())
+                others = delta.getOtherPredecessors(pcs);
+            if (others.isEmpty())
+                others = delta.getOtherSuccessors(pcs);
 
+            for (Pcs<T> otherPcs : others) {
                 if (base.contains(otherPcs)) {
                     delta.remove(otherPcs);
                 } else if (base.contains(pcs)) {