Fix Parsing Bug with Update By Query for Stored Scripts (#29039)

This changes the parsing logic for stored scripts in update by query to match the parsing logic for scripts in general Elasticsearch.

Closes #28002

modules/reindex/src/main/java/org/elasticsearch/index/reindex/RestUpdateByQueryAction.java

@@ -86,7 +86,7 @@ public class RestUpdateByQueryAction extends AbstractBulkByQueryRestHandler<Upda
             Map<String,Object> configMap = (Map<String, Object>) config;
             String script = null;
             ScriptType type = null;
-            String lang = DEFAULT_SCRIPT_LANG;
+            String lang = null;
             Map<String, Object> params = Collections.emptyMap();
             for (Iterator<Map.Entry<String, Object>> itr = configMap.entrySet().iterator(); itr.hasNext();) {
                 Map.Entry<String, Object> entry = itr.next();
@@ -126,7 +126,15 @@ public class RestUpdateByQueryAction extends AbstractBulkByQueryRestHandler<Upda
             }
             assert type != null : "if script is not null, type should definitely not be null";
 
-            return new Script(type, lang, script, params);
+            if (type == ScriptType.STORED) {
+                if (lang != null) {
+                    throw new IllegalArgumentException("lang cannot be specified for stored scripts");
+                }
+
+                return new Script(type, null, script, null, params);
+            } else {
+                return new Script(type, lang == null ? DEFAULT_SCRIPT_LANG : lang, script, params);
+            }
         } else {
             throw new IllegalArgumentException("Script value should be a String or a Map");
         }

qa/smoke-test-reindex-with-all-modules/src/test/resources/rest-api-spec/test/update_by_query/10_script.yml

@@ -340,3 +340,84 @@
             source: if (ctx._source.user == "kimchy") {ctx.op = "index"} else {ctx.op = "junk"}
 
   - match: { error.reason: 'Operation type [junk] not allowed, only [noop, index, delete] are allowed' }
+
+---
+"Update all docs with one deletion and one noop using a stored script":
+  - do:
+      index:
+        index:  twitter
+        type:   tweet
+        id:     1
+        body:   { "level": 9, "last_updated": "2016-01-01T12:10:30Z" }
+  - do:
+      index:
+        index:  twitter
+        type:   tweet
+        id:     2
+        body:   { "level": 10, "last_updated": "2016-01-01T12:10:30Z" }
+  - do:
+      index:
+        index:  twitter
+        type:   tweet
+        id:     3
+        body:   { "level": 11, "last_updated": "2016-01-01T12:10:30Z" }
+  - do:
+      index:
+        index:  twitter
+        type:   tweet
+        id:     4
+        body:   { "level": 12, "last_updated": "2016-01-01T12:10:30Z" }
+  - do:
+      indices.refresh: {}
+  - do:
+      put_script:
+        id: "my_update_script"
+        body: { "script": {"lang": "painless",
+                "source": "int choice = ctx._source.level % 3;
+                               if (choice == 0) {
+                                   ctx._source.last_updated = '2016-01-02T00:00:00Z';
+                               } else if (choice == 1) {
+                                   ctx.op = 'noop';
+                               } else {
+                                   ctx.op = 'delete';
+                               }" } }
+  - match: { acknowledged: true }
+
+  - do:
+      update_by_query:
+        refresh: true
+        index:   twitter
+        body:
+          script:
+             id: "my_update_script"
+
+  - match: {updated: 2}
+  - match: {deleted: 1}
+  - match: {noops: 1}
+
+  - do:
+      search:
+        index: twitter
+        body:
+          query:
+            match:
+              last_updated: "2016-01-02T00:00:00Z"
+  - match: { hits.total: 2 }
+
+  - do:
+      search:
+        index: twitter
+        body:
+          query:
+            match:
+              last_updated: "2016-01-01T12:10:30Z"
+  - match: { hits.total: 1 }
+
+  - do:
+      search:
+        index: twitter
+        body:
+          query:
+            term:
+              level: 11
+  - match: { hits.total: 0 }