Scripting: Add score() back to AbstractSearchScript

See #8377
closes #8416
closes #8417

src/main/java/org/elasticsearch/script/AbstractSearchScript.java

@@ -24,6 +24,7 @@ import org.apache.lucene.search.Scorer;
 import org.elasticsearch.index.fielddata.ScriptDocValues;
 import org.elasticsearch.search.lookup.*;
 
+import java.io.IOException;
 import java.util.Map;
 
 /**
@@ -38,6 +39,7 @@ import java.util.Map;
 public abstract class AbstractSearchScript extends AbstractExecutableScript implements SearchScript {
 
     private SearchLookup lookup;
+    private Scorer scorer;
 
     /**
      * Returns the doc lookup allowing to access field data (cached) values as well as the current document score
@@ -47,6 +49,13 @@ public abstract class AbstractSearchScript extends AbstractExecutableScript impl
         return lookup.doc();
     }
 
+    /**
+     * Returns the current score and only applicable when used as a scoring script in a custom score query!.
+     */
+    protected final float score() throws IOException {
+        return scorer.score();
+    }
+
     /**
      * Returns field data strings access for the provided field.
      */
@@ -95,7 +104,7 @@ public abstract class AbstractSearchScript extends AbstractExecutableScript impl
 
     @Override
     public void setScorer(Scorer scorer) {
-        throw new UnsupportedOperationException();
+        this.scorer = scorer;
     }
 
     @Override