skip trailing delimiter on comment lines in printComment

Author: rootvector2

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

@@ -246,7 +246,7 @@ public void printComment(final String comment) throws IOException {
                     }
                     // falls-through: break intentionally excluded.
                 case LF:
-                    println();
+                    printCommentSeparator();
                     appendable.append(format.getCommentMarker().charValue()); // Explicit unboxing is intentional
                     appendable.append(SP);
                     break;
@@ -255,12 +255,26 @@ public void printComment(final String comment) throws IOException {
                     break;
                 }
             }
-            println();
+            printCommentSeparator();
         } finally {
             lock.unlock();
         }
     }
 
+    /**
+     * Ends a comment line with the record separator only. A comment is not a record, so the trailing delimiter that
+     * {@link #println()} writes must not follow it.
+     *
+     * @throws IOException If an I/O error occurs.
+     */
+    private void printCommentSeparator() throws IOException {
+        final String recordSeparator = format.getRecordSeparator();
+        if (recordSeparator != null) {
+            appendable.append(recordSeparator);
+        }
+        newRecord = true;
+    }
+
     /**
      * Prints headers for a result set based on its metadata.
      *

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

@@ -1107,6 +1107,38 @@ void testMultiLineComment() throws IOException {
         }
     }
 
+    @Test
+    void testMultiLineCommentWithTrailingDelimiter() throws IOException {
+        // A comment is not a record, so the trailing delimiter must not follow comment lines, or it becomes
+        // part of the comment text on read back. The following data record still gets its trailing delimiter.
+        final CSVFormat format = CSVFormat.DEFAULT.builder().setCommentMarker('#').setTrailingDelimiter(true).get();
+        final StringWriter sw = new StringWriter();
+        try (CSVPrinter printer = new CSVPrinter(sw, format)) {
+            printer.printComment("This is a comment\non multiple lines");
+            printer.printRecord("A", "B");
+        }
+        final String string = sw.toString();
+        assertEquals("# This is a comment" + RECORD_SEPARATOR + "# on multiple lines" + RECORD_SEPARATOR + "A,B," + RECORD_SEPARATOR, string);
+        try (CSVParser parser = CSVParser.parse(string, format)) {
+            final List<CSVRecord> records = parser.getRecords();
+            assertEquals(1, records.size());
+            assertEquals("This is a comment\non multiple lines", records.get(0).getComment());
+            assertEquals("A", records.get(0).get(0));
+            assertEquals("B", records.get(0).get(1));
+        }
+    }
+
+    @Test
+    void testMultiLineCommentWithoutRecordSeparator() throws IOException {
+        // A null record separator writes nothing between comment lines, matching the record output path.
+        final CSVFormat format = CSVFormat.DEFAULT.builder().setCommentMarker('#').setRecordSeparator(null).get();
+        final StringWriter sw = new StringWriter();
+        try (CSVPrinter printer = new CSVPrinter(sw, format)) {
+            printer.printComment("a\nb");
+        }
+        assertEquals("# a# b", sw.toString());
+    }
+
     @Test
     void testMySqlNullOutput() throws IOException {
         Object[] s = new String[] { "NULL", null };