From 43ad7806eb765c202a0151c4a47ebd9defb52d60 Mon Sep 17 00:00:00 2001
From: Noa Resare <noa@resare.com>
Date: Thu, 16 Jun 2022 10:20:03 +0100
Subject: [PATCH] Ensure that empty TXT records always renders as ""

Instantiating an empty TXT record using Record.fromString() would
previously render as a TXT without the empty string.

Closes #254
---
 src/main/java/org/xbill/DNS/TXTBase.java    | 4 ++++
 src/test/java/org/xbill/DNS/RecordTest.java | 8 ++++++++
 2 files changed, 12 insertions(+)

diff --git a/src/main/java/org/xbill/DNS/TXTBase.java b/src/main/java/org/xbill/DNS/TXTBase.java
index 7117502f..96694b12 100644
--- a/src/main/java/org/xbill/DNS/TXTBase.java
+++ b/src/main/java/org/xbill/DNS/TXTBase.java
@@ -73,6 +73,10 @@ protected void rdataFromString(Tokenizer st, Name origin) throws IOException {
   /** converts to a String */
   @Override
   protected String rrToString() {
+    if (strings.isEmpty()) {
+      // always return at least an empty quoted String
+      return "\"\"";
+    }
     StringBuilder sb = new StringBuilder();
     Iterator<byte[]> it = strings.iterator();
     while (it.hasNext()) {
diff --git a/src/test/java/org/xbill/DNS/RecordTest.java b/src/test/java/org/xbill/DNS/RecordTest.java
index e35041af..b00cfc78 100644
--- a/src/test/java/org/xbill/DNS/RecordTest.java
+++ b/src/test/java/org/xbill/DNS/RecordTest.java
@@ -912,4 +912,12 @@ void testSerializable() throws IOException {
       }
     }
   }
+
+  // https://github.com/dnsjava/dnsjava/issues/254
+  @Test
+  void testEmptyTXTSerialization() throws IOException {
+    Name recordName = Name.fromString("name.name.");
+    Record r = Record.fromString(recordName, Type.TXT, DClass.IN, 0, "", recordName);
+    assertEquals("name.name.\t\t0\tIN\tTXT\t\"\"", r.toString());
+  }
 }