From ff74ba1807c7a6226d3dab818472f9657b0f178e Mon Sep 17 00:00:00 2001
From: Wleeaf <179125857+wleeaf@users.noreply.github.com>
Date: Sun, 25 Oct 2026 14:25:01 +0000
Subject: [PATCH] fix: drop a backslash at the end of the input

When the input ended with a backslash, the parser read the end of the
stream (-1) as the escaped character and stored it as '\uffff'. So
"foo=bar\" at the end of a file without a final newline loaded as
"bar\uffff", and a key ending there got the same extra character.
java.util.Properties drops such a backslash and loads "bar".

The trailing backslash now stays in the raw text, so the file is
written back unchanged, but it is left out of the key or value.
---
 .../org/codejive/properties/PropertiesParser.java    |  7 +++++++
 .../codejive/properties/TestPropertiesParser.java    | 12 ++++++++++++
 2 files changed, 19 insertions(+)

diff --git a/src/main/java/org/codejive/properties/PropertiesParser.java b/src/main/java/org/codejive/properties/PropertiesParser.java
index 8a37551..c1649c5 100644
--- a/src/main/java/org/codejive/properties/PropertiesParser.java
+++ b/src/main/java/org/codejive/properties/PropertiesParser.java
@@ -272,6 +272,10 @@ private void addChar(int ch) throws IOException {
         if (ch == '\\') {
             hasEscapes = true;
             int ch2 = readChar();
+            if (isEof(ch2)) {
+                // A backslash at the end of the input escapes nothing
+                return;
+            }
             str.append((char) ch2);
             if (ch2 == 'u') {
                 for (int i = 0; i < 4; i++) {
@@ -315,6 +319,9 @@ public static String unescape(String escape) {
         for (int i = 0; i < escape.length(); i++) {
             char ch = escape.charAt(i);
             if (ch == '\\') {
+                if (i == escape.length() - 1) {
+                    break;
+                }
                 ch = escape.charAt(++i);
                 switch (ch) {
                     case 't':
diff --git a/src/test/java/org/codejive/properties/TestPropertiesParser.java b/src/test/java/org/codejive/properties/TestPropertiesParser.java
index f967642..333ae40 100644
--- a/src/test/java/org/codejive/properties/TestPropertiesParser.java
+++ b/src/test/java/org/codejive/properties/TestPropertiesParser.java
@@ -131,4 +131,16 @@ void testMissingSeparatorAndValueAtEof() throws IOException {
                         new Token(Type.SEPARATOR, ""),
                         new Token(Type.VALUE, ""));
     }
+
+    @Test
+    void testBackslashAtEof() throws IOException {
+        List<Token> tokens =
+                PropertiesParser.tokens(new StringReader("foo=bar\\")).collect(Collectors.toList());
+
+        assertThat(tokens)
+                .containsExactly(
+                        new Token(Type.KEY, "foo"),
+                        new Token(Type.SEPARATOR, "="),
+                        new Token(Type.VALUE, "bar\\", "bar"));
+    }
 }