Fixed #69

release-notes/VERSION

@@ -8,6 +8,8 @@ Project: jackson-dataformat-csv
 
 #66: Deserializing an empty string as an array field return a non-empty list of one empty String
  (reported by aksh3ll@github)
+#69: SequenceWriter#write(null) writes a single null, not an entire row of nulls
+ (reported by georgewfraser@github)
 
 2.5.1 (06-Feb-2015)
 

src/main/java/com/fasterxml/jackson/dataformat/csv/CsvGenerator.java

@@ -621,6 +621,13 @@ public void writeNull() throws IOException
         if (!_skipValue) {
             if (_arraySeparator >= 0) {
                 _addToArray(_schema.getNullValue());
+            } else if (_writeContext.inRoot()) { // as per [#69]
+                // or, to write 'empty Object' (for common case), would
+                // write single null, then finish row, like so:
+                /*
+                _writer.writeNull(_columnIndex());
+                finishRow();
+*/
             } else {
                 _writer.writeNull(_columnIndex());
             }

src/test/java/com/fasterxml/jackson/dataformat/csv/ser/NullWritingTest.java

@@ -0,0 +1,64 @@
+package com.fasterxml.jackson.dataformat.csv.ser;
+
+import java.io.ByteArrayOutputStream;
+import java.io.StringWriter;
+
+import com.fasterxml.jackson.databind.*;
+import com.fasterxml.jackson.dataformat.csv.*;
+
+// for [dataformat-csv#69]
+public class NullWritingTest extends ModuleTestBase
+{
+    private final CsvMapper csv = new CsvMapper();
+
+    public static class Nullable {
+        public String a, b, c, d;
+    }
+
+    public void testObjectWithNullMembersToString() throws Exception {
+        CsvSchema schema = csv.schemaFor(Nullable.class).withUseHeader(true);
+        ObjectWriter writer = csv.writer(schema);
+        String nullMembers = writer.writeValueAsString(new Nullable());    
+        assertEquals("a,b,c,d\n,,,\n", nullMembers);
+    }
+
+    public void testNullToString() throws Exception {
+        CsvSchema schema = csv.schemaFor(Nullable.class).withUseHeader(true);
+        ObjectWriter writer = csv.writer(schema);
+        String nullObject = writer.writeValueAsString(null);
+        assertEquals("a,b,c,d\n", nullObject);
+    }
+
+    public void testObjectWithNullMembersToStream() throws Exception {
+        CsvSchema schema = csv.schemaFor(Nullable.class).withUseHeader(true);
+        ObjectWriter writer = csv.writer(schema);
+
+        // Write an object with null members
+        ByteArrayOutputStream stream = new ByteArrayOutputStream();
+        SequenceWriter writeValues = writer.writeValues(stream);
+        writeValues.write(new Nullable());
+        writeValues.write(new Nullable());
+        writeValues.flush();
+        String nullMembers = stream.toString("UTF-8");
+        assertEquals("a,b,c,d\n,,,\n,,,\n", nullMembers);
+    }
+
+    public void testNullToStream() throws Exception {
+        CsvSchema schema = csv.schemaFor(Nullable.class).withUseHeader(true);
+        ObjectWriter writer = csv.writer(schema);
+
+        // Write a null value
+        StringWriter sw = new StringWriter();
+        SequenceWriter writeValues = writer.writeValues(sw);
+        writeValues.write(null);
+        writeValues.write(null);
+        writeValues.flush();
+        String nullObject = sw.toString();
+        /* 11-Feb-2015, tatu: Two ways to go; either nulls get ignored, or they trigger serialization of
+         *   empty Object. For now, former occurs:
+         */
+
+        assertEquals("a,b,c,d\n", nullObject);
+//        assertEquals("a,b,c,d\n\n\n", nullObject);
+    } 
+}