From dd986794dd95f6294af87717893728ffe1653916 Mon Sep 17 00:00:00 2001
From: Daeun Kim <150661115+dani1552@users.noreply.github.com>
Date: Sat, 8 Aug 2026 18:25:45 +0900
Subject: [PATCH] [ZEPPELIN-6507] Return empty list from
 FileInterpreter.completion()

---
 .../org/apache/zeppelin/file/FileInterpreter.java   |  3 ++-
 .../apache/zeppelin/file/FileInterpreterTest.java   | 13 +++++++++++++
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/file/src/main/java/org/apache/zeppelin/file/FileInterpreter.java b/file/src/main/java/org/apache/zeppelin/file/FileInterpreter.java
index 286d315ba83..50592cc5f35 100644
--- a/file/src/main/java/org/apache/zeppelin/file/FileInterpreter.java
+++ b/file/src/main/java/org/apache/zeppelin/file/FileInterpreter.java
@@ -24,6 +24,7 @@
 import java.nio.file.Path;
 import java.nio.file.Paths;
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Properties;
@@ -167,6 +168,6 @@ public Scheduler getScheduler() {
   @Override
   public List<InterpreterCompletion> completion(String buf, int cursor,
       InterpreterContext interpreterContext) {
-    return null;
+    return Collections.emptyList();
   }
 }
diff --git a/file/src/test/java/org/apache/zeppelin/file/FileInterpreterTest.java b/file/src/test/java/org/apache/zeppelin/file/FileInterpreterTest.java
index 6097d5fc59b..01066a1fed6 100644
--- a/file/src/test/java/org/apache/zeppelin/file/FileInterpreterTest.java
+++ b/file/src/test/java/org/apache/zeppelin/file/FileInterpreterTest.java
@@ -19,12 +19,15 @@
 package org.apache.zeppelin.file;
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 import static org.junit.jupiter.api.Assertions.assertFalse;
 
+import java.util.List;
 import java.util.Properties;
 
 import org.apache.zeppelin.interpreter.InterpreterException;
+import org.apache.zeppelin.interpreter.thrift.InterpreterCompletion;
 import org.junit.jupiter.api.Test;
 
 /**
@@ -178,4 +181,14 @@ void testComplexCommand() {
     assertTrue(args.flags.contains('h'));
     assertFalse(args.flags.contains('-'));
   }
+
+  @Test
+  void testCompletionReturnsEmptyListInsteadOfNull() {
+    TestFileInterpreter interpreter = new TestFileInterpreter(new Properties());
+
+    List<InterpreterCompletion> completions = interpreter.completion("ls", 2, null);
+
+    assertNotNull(completions, "completion() should never return null");
+    assertTrue(completions.isEmpty(), "Default completion() should return an empty list");
+  }
 }