[CSV-254] POSTGRESQL_CSV cannot parse correctly (null vs zero-length

string)

Add test

Author: garydgregory

pom.xml

@@ -183,6 +183,7 @@
               <exclude>src/test/resources/org/apache/commons/csv/CSV-196/emoji.csv</exclude>
               <exclude>src/test/resources/org/apache/commons/csv/CSV-196/japanese.csv</exclude>
               <exclude>src/test/resources/org/apache/commons/csv/CSV-213/999751170.patch.csv</exclude>
+              <exclude>src/test/resources/org/apache/commons/csv/CSV-254/csv-254.csv</exclude>
               <exclude>src/test/resources/org/apache/commons/csv/CSVFileParser/bom.csv</exclude>
               <exclude>src/test/resources/org/apache/commons/csv/CSVFileParser/test.csv</exclude>
               <exclude>src/test/resources/org/apache/commons/csv/CSVFileParser/test_default.txt</exclude>

src/test/java/org/apache/commons/csv/issues/JiraCsv254Test.java

@@ -0,0 +1,52 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package org.apache.commons.csv.issues;
+
+import static org.apache.commons.csv.CsvAssertions.assertValuesEquals;
+
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.nio.file.Paths;
+import java.util.Iterator;
+
+import org.apache.commons.csv.CSVFormat;
+import org.apache.commons.csv.CSVParser;
+import org.apache.commons.csv.CSVRecord;
+import org.junit.jupiter.api.Test;
+
+/**
+ * Tests https://issues.apache.org/jira/browse/CSV-254.
+ */
+class JiraCsv254Test {
+
+    @Test
+    void test() throws IOException {
+        final CSVFormat csvFormat = CSVFormat.POSTGRESQL_CSV;
+        try (BufferedReader reader = Files.newBufferedReader(Paths.get("src/test/resources/org/apache/commons/csv/CSV-254/csv-254.csv"),
+                StandardCharsets.UTF_8); CSVParser parser = csvFormat.parse(reader)) {
+            final Iterator<CSVRecord> csvRecords = parser.iterator();
+            assertValuesEquals(new String[] { "AA", "33", null }, csvRecords.next());
+            assertValuesEquals(new String[] { "AA", null, "" }, csvRecords.next());
+            assertValuesEquals(new String[] { null, "33", "CC" }, csvRecords.next());
+        }
+    }
+}

src/test/resources/org/apache/commons/csv/CSV-254/csv-254.csv

@@ -0,0 +1,3 @@
+AA,33,
+AA,,""
+,33,CC