Scripting: Add explicit error message when script_score script returns NaN

When a scoring script returns not a number, the current message is confusing (IllegalArgumentException[docID must be >= 0 and < maxDoc=3 (got docID=2147483647)]). This commit adds the error message ScriptException[script score function returns a wrong score: NaN].

Closes #2426

src/main/java/org/elasticsearch/common/lucene/search/function/ScriptScoreFunction.java

@@ -22,6 +22,7 @@ package org.elasticsearch.common.lucene.search.function;
 import org.apache.lucene.index.LeafReaderContext;
 import org.apache.lucene.search.Explanation;
 import org.apache.lucene.search.Scorer;
+import org.elasticsearch.script.ScriptException;
 import org.elasticsearch.script.SearchScript;
 
 import java.io.IOException;
@@ -96,7 +97,11 @@ public class ScriptScoreFunction extends ScoreFunction {
         script.setNextDocId(docId);
         scorer.docid = docId;
         scorer.score = subQueryScore;
-        return script.runAsDouble();
+        double result = script.runAsDouble();
+        if (Double.isNaN(result)) {
+            throw new ScriptException("script_score returned NaN");
+        }
+        return result;
     }
 
     @Override

src/test/java/org/elasticsearch/common/lucene/search/function/ScriptScoreFunctionTests.java

@@ -0,0 +1,64 @@
+/*
+ * Licensed to Elasticsearch under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch licenses this file to you under
+ * the Apache License, Version 2.0 (the "License"); you may
+ * not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package org.elasticsearch.common.lucene.search.function;
+
+import org.elasticsearch.script.AbstractFloatSearchScript;
+import org.elasticsearch.script.ScriptException;
+import org.elasticsearch.test.ElasticsearchTestCase;
+import org.junit.Test;
+
+import static org.hamcrest.Matchers.equalTo;
+
+public class ScriptScoreFunctionTests extends ElasticsearchTestCase {
+
+    /**
+     * Tests https://github.com/elasticsearch/elasticsearch/issues/2426
+     */
+    @Test
+    public void testScriptScoresReturnsNaN() {
+        try {
+            ScoreFunction scoreFunction = new ScriptScoreFunction("Float.NaN", null, new FloatValueScript(Float.NaN));
+            scoreFunction.score(randomInt(), randomFloat());
+            fail("should have thrown an exception about the script_score returning NaN");
+        } catch (ScriptException e) {
+            assertThat("message contains error about script_score returning NaN: " + e.getMessage(),
+                    e.getMessage().contains("NaN"), equalTo(true));
+        }
+    }
+
+    static class FloatValueScript extends AbstractFloatSearchScript {
+
+        private final float value;
+
+        FloatValueScript(float value) {
+            this.value = value;
+        }
+
+        @Override
+        public float runAsFloat() {
+            return value;
+        }
+
+        @Override
+        public void setNextDocId(int doc) {
+            // nothing here
+        }
+    }
+}

src/test/java/org/elasticsearch/search/functionscore/FunctionScoreTests.java

@@ -169,7 +169,7 @@ public class FunctionScoreTests extends ElasticsearchIntegrationTest {
 
         assertThat(responseWithWeights.getHits().getAt(0).getExplanation().toString(),
                 equalTo("6.0 = (MATCH) function score, product of:\n  1.0 = (MATCH) ConstantScore(text_field:value), product of:\n    1.0 = boost\n    1.0 = queryNorm\n  6.0 = (MATCH) Math.min of\n    6.0 = (MATCH) function score, score mode [multiply]\n      1.0 = (MATCH) function score, product of:\n        1.0 = match filter: *:*\n        1.0 = (MATCH) Function for field geo_point_field:\n          1.0 = exp(-0.5*pow(MIN of: [Math.max(arcDistance([10.0, 20.0](=doc value),[10.0, 20.0](=origin)) - 0.0(=offset), 0)],2.0)/7.213475204444817E11)\n      2.0 = (MATCH) function score, product of:\n        1.0 = match filter: *:*\n        2.0 = (MATCH) product of:\n          1.0 = field value function: ln(doc['double_field'].value * factor=1.0)\n          2.0 = weight\n      3.0 = (MATCH) function score, product of:\n        1.0 = match filter: *:*\n        3.0 = (MATCH) product of:\n          1.0 = script score function, computed with script:\"_index['text_field']['value'].tf()\n          3.0 = weight\n    3.4028235E38 = maxBoost\n  1.0 = queryBoost\n")
-                );
+        );
         responseWithWeights = client().search(
                 searchRequest().source(
                         searchSource().query(