Adds deprecation logging to ScriptDocValues#getValues.

First commit addressing issue #22919.

`ScriptDocValues#getValues` was added for backwards compatibility but no
longer needed. Scripts using the syntax `doc.foo.values.bar` should be
using `doc.foo.bar` instead.

server/src/main/java/org/elasticsearch/index/fielddata/ScriptDocValues.java

@@ -26,15 +26,20 @@
 import org.elasticsearch.common.geo.GeoHashUtils;
 import org.elasticsearch.common.geo.GeoPoint;
 import org.elasticsearch.common.geo.GeoUtils;
+import org.elasticsearch.common.logging.DeprecationLogger;
+import org.elasticsearch.common.logging.ESLoggerFactory;
 import org.elasticsearch.script.JodaCompatibleZonedDateTime;
 
 import java.io.IOException;
+import java.security.AccessController;
+import java.security.PrivilegedAction;
 import java.time.Instant;
 import java.time.ZoneOffset;
 import java.util.AbstractList;
 import java.util.Arrays;
 import java.util.Comparator;
 import java.util.List;
+import java.util.function.BiConsumer;
 import java.util.function.UnaryOperator;
 
 /**
@@ -48,6 +53,25 @@
  */
 public abstract class ScriptDocValues<T> extends AbstractList<T> {
 
+    private static final DeprecationLogger deprecationLogger = new DeprecationLogger(ESLoggerFactory.getLogger(ScriptDocValues.class));
+    /**
+     * Callback for deprecated fields. In production this should always point to
+     * {@link #deprecationLogger} but tests will override it so they can test
+     * that we use the required permissions when calling it.
+     */
+    private final BiConsumer<String, String> deprecationCallback;
+
+    public ScriptDocValues() {
+        deprecationCallback = deprecationLogger::deprecatedAndMaybeLog;
+    }
+
+    /**
+     * Constructor for testing deprecation callback.
+     */
+    ScriptDocValues(BiConsumer<String, String> deprecationCallback) {
+        this.deprecationCallback = deprecationCallback;
+    }
+
     /**
      * Set the current doc ID.
      */
@@ -57,6 +81,8 @@ public abstract class ScriptDocValues<T> extends AbstractList<T> {
      * Return a copy of the list of the values for the current document.
      */
     public final List<T> getValues() {
+        deprecated("ScriptDocValues#getValues", "Deprecated getValues used, values should be accessed directly "
+                + "(e.g., doc.foo.bar instead of doc.foo.values.bar)");
         return this;
     }
 
@@ -86,6 +112,21 @@ public final void sort(Comparator<? super T> c) {
         throw new UnsupportedOperationException("doc values are unmodifiable");
     }
 
+    /**
+     * Log a deprecation log, with the server's permissions and not the permissions
+     * of the script calling this method. We need to do this to prevent errors
+     * when rolling the log file.
+     */
+    private void deprecated(String key, String message) {
+        AccessController.doPrivileged(new PrivilegedAction<Void>() {
+            @Override
+            public Void run() {
+                deprecationCallback.accept(key, message);
+                return null;
+            }
+        });
+    }
+
     public static final class Longs extends ScriptDocValues<Long> {
         private final SortedNumericDocValues in;
         private long[] values = new long[0];