Add tests related to derived fields for QueryShardContext changes

Signed-off-by: Rishabh Maurya <rishabhmaurya05@gmail.com>

Author: rishabhmaurya

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

@@ -37,7 +37,7 @@ private static DerivedFieldMapper toType(FieldMapper in) {
      */
     public static class Builder extends ParametrizedFieldMapper.Builder {
         // TODO: The type of parameter may change here if the actual underlying FieldType object is needed
-        private final Parameter<String> type = Parameter.stringParam("type", false, m -> toType(m).type, "text");
+        private final Parameter<String> type = Parameter.stringParam("type", false, m -> toType(m).type, "keyword");
 
         private final Parameter<Script> script = new Parameter<>(
             "script",

server/src/test/java/org/opensearch/index/query/QueryShardContextTests.java

@@ -31,6 +31,7 @@
 
 package org.opensearch.index.query;
 
+import org.apache.lucene.analysis.standard.StandardAnalyzer;
 import org.apache.lucene.document.Field;
 import org.apache.lucene.document.StringField;
 import org.apache.lucene.index.DirectoryReader;
@@ -63,9 +64,14 @@
 import org.opensearch.index.fielddata.LeafFieldData;
 import org.opensearch.index.fielddata.ScriptDocValues;
 import org.opensearch.index.fielddata.plain.AbstractLeafOrdinalsFieldData;
+import org.opensearch.index.mapper.ContentPath;
+import org.opensearch.index.mapper.DerivedFieldMapper;
+import org.opensearch.index.mapper.DocumentMapper;
 import org.opensearch.index.mapper.IndexFieldMapper;
 import org.opensearch.index.mapper.MappedFieldType;
+import org.opensearch.index.mapper.Mapper;
 import org.opensearch.index.mapper.MapperService;
+import org.opensearch.index.mapper.MappingLookup;
 import org.opensearch.index.mapper.TextFieldMapper;
 import org.opensearch.search.lookup.LeafDocLookup;
 import org.opensearch.search.lookup.LeafSearchLookup;
@@ -118,6 +124,25 @@ public void testFailIfFieldMappingNotFound() {
         assertThat(result.name(), equalTo("name"));
     }
 
+    public void testDerivedFieldMapping() {
+        QueryShardContext context = createQueryShardContext(IndexMetadata.INDEX_UUID_NA_VALUE, null);
+        assertNull(context.failIfFieldMappingNotFound("test_derived", null));
+        DocumentMapper documentMapper = mock(DocumentMapper.class);
+        Mapper.BuilderContext builderContext = new Mapper.BuilderContext(Settings.EMPTY, new ContentPath(0));
+        DerivedFieldMapper derivedFieldMapper = new DerivedFieldMapper.Builder("test_derived").build(builderContext);
+        MappingLookup mappingLookup = new MappingLookup(
+            Collections.singletonList(derivedFieldMapper),
+            Collections.emptyList(),
+            Collections.emptyList(),
+            0,
+            new StandardAnalyzer()
+        );
+        when(documentMapper.mappers()).thenReturn(mappingLookup);
+        context.setDerivedFieldMappers(documentMapper);
+        context.setAllowUnmappedFields(false);
+        assertEquals(derivedFieldMapper.fieldType(), context.failIfFieldMappingNotFound("test_derived", null));
+    }
+
     public void testToQueryFails() {
         QueryShardContext context = createQueryShardContext(IndexMetadata.INDEX_UUID_NA_VALUE, null);
         Exception exc = expectThrows(Exception.class, () -> context.toQuery(new AbstractQueryBuilder() {