Migrate constant BellmanFordResult.EMPTY to method

Co-authored-by: Ioannis Panagiotas <ioannis.panagiotas@neotechnology.com>

Author: vnickolov

algo/src/main/java/org/neo4j/gds/paths/bellmanford/BellmanFordResult.java

@@ -26,10 +26,12 @@ public record BellmanFordResult(
     PathFindingResult negativeCycles,
     boolean containsNegativeCycle
 ) {
-    public static final BellmanFordResult EMPTY = new BellmanFordResult(
-        PathFindingResult.empty(),
-        PathFindingResult.empty(),
-        false
-    );
+    public static BellmanFordResult empty() {
+        return new BellmanFordResult(
+            PathFindingResult.empty(),
+            PathFindingResult.empty(),
+            false
+        );
+    }
 
 }

algorithms-compute-facade/src/main/java/org/neo4j/gds/pathfinding/PathFindingComputeFacade.java

@@ -149,7 +149,7 @@ public CompletableFuture<BellmanFordResult> bellmanFord(
     ) {
         // If the input graph is empty return a completed future with empty result
         if (graph.isEmpty()) {
-            return CompletableFuture.completedFuture(BellmanFordResult.EMPTY);
+            return CompletableFuture.completedFuture(BellmanFordResult.empty());
         }
 
         // Create ProgressTracker

algorithms-compute-facade/src/test/java/org/neo4j/gds/pathfinding/PathFindingComputeFacadeEmptyGraphTest.java

@@ -36,7 +36,6 @@
 import org.neo4j.gds.kspanningtree.KSpanningTreeParameters;
 import org.neo4j.gds.paths.astar.AStarParameters;
 import org.neo4j.gds.paths.bellmanford.BellmanFordParameters;
-import org.neo4j.gds.paths.bellmanford.BellmanFordResult;
 import org.neo4j.gds.paths.delta.DeltaSteppingParameters;
 import org.neo4j.gds.paths.dijkstra.DijkstraSingleSourceParameters;
 import org.neo4j.gds.paths.dijkstra.DijkstraSourceTargetParameters;
@@ -110,7 +109,14 @@ void bellmanFord() {
         var result = future.join();
 
         assertThat(result).isNotNull();
-        assertThat(result).isEqualTo(BellmanFordResult.EMPTY);
+        assertThat(result.shortestPaths())
+            .extracting(PathFindingResult::pathSet)
+            .asInstanceOf(SET)
+            .isEmpty();
+        assertThat(result.negativeCycles())
+            .extracting(PathFindingResult::pathSet)
+            .asInstanceOf(SET)
+            .isEmpty();
 
         verifyNoInteractions(progressTrackerFactoryMock);
         verifyNoInteractions(algorithmCallerMock);

procedures/pushback-procedures-facade/src/test/java/org/neo4j/gds/procedures/algorithms/pathfinding/BellmanFordStreamResultTransformerTest.java

@@ -51,7 +51,7 @@ void shouldReturnEmptyStreamOnEmptyResult() {
             pathFactoryFacadeMock
         );
 
-        var streamResult = transformer.apply(BellmanFordResult.EMPTY);
+        var streamResult = transformer.apply(BellmanFordResult.empty());
         assertThat(streamResult).isEmpty();
 
         verifyNoInteractions(graphMock);