Skip byte counting at EOF in ExtendedBufferedReader.read

src/main/java/org/apache/commons/csv/ExtendedBufferedReader.java

@@ -210,7 +210,7 @@ public int read() throws IOException {
         if (current == CR || current == LF && lastChar != CR || current == EOF && lastChar != CR && lastChar != LF && lastChar != EOF) {
             lineNumber++;
         }
-        if (encoder != null) {
+        if (encoder != null && current != EOF) {
             this.bytesRead += getEncodedCharLength(current);
         }
         lastChar = current;

src/test/java/org/apache/commons/csv/CSVParserTest.java

@@ -691,6 +691,27 @@ void testGetBytePositionMultiCharacterDelimiterWithSupplementaryCharacter() thro
         }
     }
 
+    @Test
+    void testGetBytePositionWithSingleByteCharset() throws IOException {
+        // A single-byte charset cannot encode U+FFFF, the char value of the EOF sentinel.
+        // Byte counting must skip the EOF read so a valid file parses without throwing.
+        final String code = "a,b\nc,d\n";
+        try (CSVParser parser = CSVParser.builder()
+                .setReader(new StringReader(code))
+                .setFormat(CSVFormat.DEFAULT)
+                .setCharset(StandardCharsets.ISO_8859_1)
+                .setTrackBytes(true)
+                .get()) {
+            final CSVRecord first = parser.nextRecord();
+            final CSVRecord second = parser.nextRecord();
+            assertNotNull(first);
+            assertNotNull(second);
+            assertNull(parser.nextRecord());
+            assertEquals(0, first.getBytePosition());
+            assertEquals(4, second.getBytePosition());
+        }
+    }
+
     @Test
     void testGetBytePositionWithCharacterOffsetAndMultiBytePrefix() throws Exception {
         final String row0 = "é,x\n";