Always write doc_values param to mapping for wildcard field

I made a mistake making this parameter default to false. In 3.0,
I would like to switch the default to true. An index upgraded from
2.x with the default (false) value should specifically emit the
value to avoid implicitly picking up the new default (true).

Signed-off-by: Michael Froh <[email protected]>

Author: msfroh

server/src/main/java/org/opensearch/index/mapper/WildcardFieldMapper.java

@@ -101,7 +101,7 @@ public static final class Builder extends ParametrizedFieldMapper.Builder {
         );
         private final Parameter<String> normalizer = Parameter.stringParam("normalizer", false, m -> toType(m).normalizerName, "default");
         private final Parameter<Map<String, String>> meta = Parameter.metaParam();
-        private final Parameter<Boolean> hasDocValues = Parameter.docValuesParam(m -> toType(m).hasDocValues, false);
+        private final Parameter<Boolean> hasDocValues = Parameter.docValuesParam(m -> toType(m).hasDocValues, false).alwaysSerialize();
         private final IndexAnalyzers indexAnalyzers;
 
         public Builder(String name, IndexAnalyzers indexAnalyzers) {

server/src/test/java/org/opensearch/index/mapper/WildcardFieldMapperTests.java

@@ -49,6 +49,7 @@ public class WildcardFieldMapperTests extends MapperTestCase {
     @Override
     protected void minimalMapping(XContentBuilder b) throws IOException {
         b.field("type", "wildcard");
+        b.field("doc_values", false);
     }
 
     @Override
@@ -59,7 +60,10 @@ protected void writeFieldValue(XContentBuilder builder) throws IOException {
     @Override
     protected void registerParameters(ParameterChecker checker) throws IOException {
         checker.registerConflictCheck("normalizer", b -> b.field("normalizer", "lowercase"));
-        checker.registerConflictCheck("doc_values", b -> b.field("doc_values", true));
+        checker.registerConflictCheck("doc_values", fieldMapping(this::minimalMapping), fieldMapping(xcb -> {
+            xcb.field("type", "wildcard");
+            xcb.field("doc_values", true);
+        }));
         checker.registerConflictCheck("null_value", b -> b.field("null_value", "foo"));
         checker.registerUpdateCheck(b -> b.field("ignore_above", 256), m -> assertEquals(256, ((WildcardFieldMapper) m).ignoreAbove()));
     }