fix: bolt layer cannot deal with EmptyPath

Returning an EmptyPath from a stored procedure works on java level, but bolt throws some strange exceptions. In case of an EmptyPath instead a empty result (aka no line) is returned. Refs: #8
THM-Graphs · Jul 7, 2024 · bb79bb2 · bb79bb2
1 parent cfd6ff0
commit bb79bb2
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diff --git a/src/main/java/atag/chains/ChainsProcedure.java b/src/main/java/atag/chains/ChainsProcedure.java
@@ -1,6 +1,5 @@
 package atag.chains;
 
-import atag.util.EmptyPath;
 import atag.util.ResultTypes;
 import org.neo4j.graphalgo.impl.util.PathImpl;
 import org.neo4j.graphdb.*;
@@ -192,7 +191,7 @@ public Stream<ResultTypes.PathResult> update(
             }
             currentNode.createRelationshipTo(afterNode, relationshipType);
         }
-        return asPathResult(builder == null ? new EmptyPath() : builder.build());
+        return builder == null ? Stream.empty() : asPathResult(builder.build());
     }
 
     private Node findNodeOrThrow(Label textLabel, String uuidProperty, String uuidText) {

diff --git a/src/main/java/atag/util/EmptyPath.java b/src/main/java/atag/util/EmptyPath.java
diff --git a/src/test/java/atag/chains/ChainsProcedureTest.java b/src/test/java/atag/chains/ChainsProcedureTest.java
@@ -29,7 +29,7 @@ public class ChainsProcedureTest {
 
     @RegisterExtension
     static Neo4jExtension neo4j = Neo4jExtension.builder()
-            .withDisabledServer()
+            //.withDisabledServer()
             .withProcedure(ChainsProcedure.class)
             /*.withFixture(db -> {
                 try {
@@ -92,20 +92,26 @@ private static void validatePathLength(GraphDatabaseService db, String query, Ma
         db.executeTransactionally(query,
                 params,
                 result -> {
-                    Path path = (Path) Iterators.single(result).get("path");
-                    if (logger.isLoggable(Level.INFO)) {
-                        StringBuilder sb = new StringBuilder();
-                        for (Node node: path.nodes()) {
-                            sb.append("(").append(node.getProperty("uuid")).append(")");
-                            if (!node.equals(path.endNode())) {
-                               sb.append("->");
-                            }
+                    Map<String, Object> singleResult = Iterators.singleOrNull(result);
+                    if (singleResult == null) {
+                        assertEquals(expectedPathLength, 0);
+                        return false;
+                    } else {
+                        Path path = (Path) singleResult.get("path");
+                        if (logger.isLoggable(Level.INFO)) {
+                            StringBuilder sb = new StringBuilder();
+                            for (Node node: path.nodes()) {
+                                sb.append("(").append(node.getProperty("uuid")).append(")");
+                                if (!node.equals(path.endNode())) {
+                                   sb.append("->");
+                                }
 
+                            }
+                            logger.info("path is %s".formatted(sb.toString()));
                         }
-                        logger.info("path is %s".formatted(sb.toString()));
+                        assertEquals(expectedPathLength, path.length(), "failed path length assertion for %s".formatted(query));
+                        assertion.accept(path);
                     }
-                    assertEquals(expectedPathLength, path.length(), "failed path length assertion for %s".formatted(query));
-                    assertion.accept(path);
                     return true;
                 });
     }
@@ -200,7 +206,7 @@ public void testTokenChain(String text, int expected, GraphDatabaseService db) {
     public static Stream<Arguments> testChainUpdate() {
 
         return Stream.of(
-                Arguments.of("removal of unbounded chain", 0, null, null, Collections.emptyList(), 0, 0, 0, null),
+                Arguments.of("removal of unbounded chain", 0, "", "", Collections.emptyList(), 0, 0, 0, null),
                 Arguments.of("removal of unbounded chain", 1, null, null, Collections.emptyList(), 0, 0, 0, null),
                 Arguments.of("removal of unbounded chain", 10, null, null, Collections.emptyList(), 0, 0, 0, null),
                 Arguments.of("removal of bounded chain", 10, "0", "9", Collections.emptyList(), 0, 2, 2, null),
@@ -223,8 +229,8 @@ public static Stream<Arguments> testChainUpdate() {
     @ParameterizedTest(name = "{index}: {0} with fixture length {1}, boundaries ({2}, {3}")
     @MethodSource
     public void testChainUpdate(String name, int fixtureLength, String uuidBefore, String uuidAfter, List<Map<String,Object>> characterList,
-                                     int expectedLength, int expectedQueryLength, int expectedNumberOfTokens, Class<Exception> exceptedException,
-                                     GraphDatabaseService db) {
+                                int expectedLength, int expectedQueryLength, int expectedNumberOfTokens, Class<Exception> exceptedException,
+                                GraphDatabaseService db) {
         String uuidText = "text";
         Map<String, Object> params = Map.of(
                 "uuidText", uuidText,
@@ -250,14 +256,6 @@ public void testChainUpdate(String name, int fixtureLength, String uuidBefore, S
 
         try {
             // cut
-            db.executeTransactionally("""
-                CALL atag.chains.update("text", $uuidBefore, $uuidAfter, $characterList, $config) YIELD path
-                RETURN path
-                """, params);
-            if (exceptedException !=null) {
-                fail("expected a exception but did not get one.");
-            }
-
             validatePathLength(db, """
                     CALL atag.chains.update("text", $uuidBefore, $uuidAfter, $characterList, $config) YIELD path
                     RETURN path
@@ -282,4 +280,5 @@ WHERE NOT (x)-[:NEXT_TOKEN]->()
             }
         }
     }
+
 }