CSV-112: HeaderMap is inconsistent when it is parsed from an input with duplicate columns names. Reported by Romain Gossé

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/csv/trunk@1592371 13f79535-47bb-0310-9956-ffa450edef68

Author: britter

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

@@ -29,6 +29,7 @@
 import java.net.URL;
 import java.nio.charset.Charset;
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.Collection;
 import java.util.Iterator;
 import java.util.LinkedHashMap;
@@ -368,6 +369,9 @@ private Map<String, Integer> initializeHeader() throws IOException {
             // build the name to index mappings
             if (header != null) {
                 for (int i = 0; i < header.length; i++) {
+                    if (hdrMap.containsKey(header[i])) {
+                        throw new IllegalStateException("The header contains duplicate names: " + Arrays.toString(header));
+                    }
                     hdrMap.put(header[i], Integer.valueOf(i));
                 }
             }

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

@@ -492,6 +492,11 @@ public void testGetHeaderMap() throws Exception {
         parser.close();
     }
 
+    @Test(expected = IllegalStateException.class)
+    public void testDuplicateHeaderEntries() throws Exception {
+        CSVParser.parse("a,b,a\n1,2,3\nx,y,z", CSVFormat.DEFAULT.withHeader(new String[]{}));
+    }
+
     @Test
     public void testGetLine() throws IOException {
         final CSVParser parser = CSVParser.parse(CSV_INPUT, CSVFormat.DEFAULT.withIgnoreSurroundingSpaces(true));