Add failing test for #130 (for now)

yaml/src/main/java/com/fasterxml/jackson/dataformat/yaml/YAMLParser.java

@@ -516,8 +516,18 @@ public JsonToken nextToken() throws IOException
     protected JsonToken _decodeScalar(ScalarEvent scalar) throws IOException
     {
         String value = scalar.getValue();
+
         _textValue = value;
         _cleanedTextValue = null;
+
+        // [dataformats-text#130]: uncomment for 2.13 either as-is, or
+        // behind a new feature
+        /*
+        if (value.isEmpty()) {
+            return JsonToken.VALUE_STRING;
+        }
+        */
+
         // we may get an explicit tag, if so, use for corroborating...
         String typeTag = scalar.getTag();
         final int len = value.length();

yaml/src/test/java/com/fasterxml/jackson/dataformat/yaml/failing/NullFromEmptyString130Test.java

@@ -0,0 +1,31 @@
+package com.fasterxml.jackson.dataformat.yaml.failing;
+
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.dataformat.yaml.ModuleTestBase;
+
+// [dataformats-text#130]: Easy enough to fix, if we choose to,
+//  but due to timing cannot include in 2.12 (too close to release
+//  after RCs)
+//
+// Fix to be done by ignoring snakeyaml's implicit type for case of
+// empty String (in `YAMLParser.
+public class NullFromEmptyString130Test extends ModuleTestBase
+{
+    static class Value130 {
+        public String value;
+
+        public void setValue(String str) {
+            value = str;
+        }
+    }
+
+    private final ObjectMapper MAPPER = newObjectMapper();
+
+    // [dataformats-text#130]
+    public void testEmptyValueToNull130() throws Exception
+    {
+        Value130 v = MAPPER.readerFor(Value130.class)
+                .readValue("value:   \n");
+        assertEquals("", v.value);
+    }
+}