improve path checks, and add a overlap splice option

src/api/java/baritone/api/pathing/calc/IPath.java

@@ -21,9 +21,9 @@ import baritone.api.Settings;
 import baritone.api.pathing.goals.Goal;
 import baritone.api.pathing.movement.IMovement;
 import baritone.api.utils.BetterBlockPos;
-import net.minecraft.util.math.BlockPos;
 import net.minecraft.world.World;
 
+import java.util.HashSet;
 import java.util.List;
 
 /**
@@ -153,9 +153,10 @@ public interface IPath {
         if (path.size() != movements.size() + 1) {
             throw new IllegalStateException("Size of path array is unexpected");
         }
+        HashSet<BetterBlockPos> seenSoFar = new HashSet<>();
         for (int i = 0; i < path.size() - 1; i++) {
-            BlockPos src = path.get(i);
-            BlockPos dest = path.get(i + 1);
+            BetterBlockPos src = path.get(i);
+            BetterBlockPos dest = path.get(i + 1);
             IMovement movement = movements.get(i);
             if (!src.equals(movement.getSrc())) {
                 throw new IllegalStateException("Path source is not equal to the movement source");
@@ -163,6 +164,10 @@ public interface IPath {
             if (!dest.equals(movement.getDest())) {
                 throw new IllegalStateException("Path destination is not equal to the movement destination");
             }
+            if (seenSoFar.contains(src)) {
+                throw new IllegalStateException("Path doubles back on itself, making a loop");
+            }
+            seenSoFar.add(src);
         }
     }
 }

src/main/java/baritone/pathing/path/PathExecutor.java

@@ -458,7 +458,7 @@ public class PathExecutor implements IPathExecutor, Helper {
         if (next == null) {
             return cutIfTooLong();
         }
-        return SplicedPath.trySplice(path, next.path).map(path -> {
+        return SplicedPath.trySplice(path, next.path, false).map(path -> {
             if (!path.getDest().equals(next.getPath().getDest())) {
                 throw new IllegalStateException();
             }

src/main/java/baritone/pathing/path/SplicedPath.java

@@ -62,7 +62,7 @@ public class SplicedPath extends PathBase {
         return numNodes;
     }
 
-    public static Optional<SplicedPath> trySplice(IPath first, IPath second) {
+    public static Optional<SplicedPath> trySplice(IPath first, IPath second, boolean allowOverlapCutoff) {
         if (second == null || first == null) {
             return Optional.empty();
         }
@@ -72,18 +72,31 @@ public class SplicedPath extends PathBase {
         if (!first.getDest().equals(second.getSrc())) {
             return Optional.empty();
         }
-        HashSet<BetterBlockPos> a = new HashSet<>(first.positions());
-        for (int i = 1; i < second.length(); i++) {
-            if (a.contains(second.positions().get(i))) {
+        HashSet<BetterBlockPos> secondPos = new HashSet<>(second.positions());
+        int firstPositionInSecond = -1;
+        for (int i = 0; i < first.length() - 1; i++) { // overlap in the very last element is fine (and required) so only go up to first.length() - 1
+            if (secondPos.contains(first.positions().get(i))) {
+                firstPositionInSecond = i;
+            }
+        }
+        if (firstPositionInSecond != -1) {
+            if (!allowOverlapCutoff) {
                 return Optional.empty();
             }
+        } else {
+            firstPositionInSecond = first.length() - 1;
+        }
+        int positionInSecond = second.positions().indexOf(first.positions().get(firstPositionInSecond));
+        if (!allowOverlapCutoff && positionInSecond != 0) {
+            throw new IllegalStateException();
         }
         List<BetterBlockPos> positions = new ArrayList<>();
         List<IMovement> movements = new ArrayList<>();
-        positions.addAll(first.positions());
-        positions.addAll(second.positions().subList(1, second.length()));
-        movements.addAll(first.movements());
-        movements.addAll(second.movements());
+        positions.addAll(first.positions().subList(0, firstPositionInSecond + 1));
+        movements.addAll(first.movements().subList(0, firstPositionInSecond));
+        
+        positions.addAll(second.positions().subList(positionInSecond + 1, second.length()));
+        movements.addAll(second.movements().subList(positionInSecond, second.length() - 1));
         return Optional.of(new SplicedPath(positions, movements, first.getNumNodesConsidered() + second.getNumNodesConsidered(), first.getGoal()));
     }
 }