Add Fields API to aggregation scripts and field scripts (#76325)

This change updates the aggregation script, map script for aggregations, and field scripts to extend 
DocBasedScript to give them access to the new fields api.

modules/lang-painless/src/main/java/org/elasticsearch/painless/PainlessPlugin.java

@@ -38,6 +38,8 @@
 import org.elasticsearch.repositories.RepositoriesService;
 import org.elasticsearch.rest.RestController;
 import org.elasticsearch.rest.RestHandler;
+import org.elasticsearch.script.AggregationScript;
+import org.elasticsearch.script.FieldScript;
 import org.elasticsearch.script.FilterScript;
 import org.elasticsearch.script.IngestScript;
 import org.elasticsearch.script.NumberSortScript;
@@ -46,6 +48,7 @@
 import org.elasticsearch.script.ScriptEngine;
 import org.elasticsearch.script.ScriptModule;
 import org.elasticsearch.script.ScriptService;
+import org.elasticsearch.script.ScriptedMetricAggContexts;
 import org.elasticsearch.script.StringSortScript;
 import org.elasticsearch.search.aggregations.pipeline.MovingFunctionScript;
 import org.elasticsearch.threadpool.ThreadPool;
@@ -140,6 +143,24 @@ public final class PainlessPlugin extends Plugin implements ScriptPlugin, Extens
         filter.add(filterWhitelist);
         map.put(FilterScript.CONTEXT, filter);
 
+        List<Whitelist> aggregation = new ArrayList<>();
+        Whitelist aggregationWhitelist =
+                WhitelistLoader.loadFromResourceFiles(PainlessPlugin.class, "org.elasticsearch.script.fields.aggregation.txt");
+        aggregation.add(aggregationWhitelist);
+        map.put(AggregationScript.CONTEXT, aggregation);
+
+        List<Whitelist> aggmap = new ArrayList<>();
+        Whitelist aggmapWhitelist =
+                WhitelistLoader.loadFromResourceFiles(PainlessPlugin.class, "org.elasticsearch.script.fields.aggmap.txt");
+        aggmap.add(aggmapWhitelist);
+        map.put(ScriptedMetricAggContexts.MapScript.CONTEXT, aggmap);
+
+        List<Whitelist> field = new ArrayList<>();
+        Whitelist fieldWhitelist =
+                WhitelistLoader.loadFromResourceFiles(PainlessPlugin.class, "org.elasticsearch.script.fields.field.txt");
+        field.add(fieldWhitelist);
+        map.put(FieldScript.CONTEXT, field);
+
         // Execute context gets everything
         List<Whitelist> test = new ArrayList<>();
         test.add(movFnWhitelist);

modules/lang-painless/src/main/resources/org/elasticsearch/painless/org.elasticsearch.script.fields.aggmap.txt

@@ -0,0 +1,15 @@
+#
+# Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+# or more contributor license agreements. Licensed under the Elastic License
+# 2.0 and the Server Side Public License, v 1; you may not use this file except
+# in compliance with, at your election, the Elastic License 2.0 or the Server
+# Side Public License, v 1.
+#
+
+# The whitelist for the fields api
+
+# The scripts must be whitelisted for painless to find the classes for the field API
+class org.elasticsearch.script.ScriptedMetricAggContexts$MapScript @no_import {
+}
+class org.elasticsearch.script.ScriptedMetricAggContexts$MapScript$Factory @no_import {
+}

modules/lang-painless/src/main/resources/org/elasticsearch/painless/org.elasticsearch.script.fields.aggregation.txt

@@ -0,0 +1,15 @@
+#
+# Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+# or more contributor license agreements. Licensed under the Elastic License
+# 2.0 and the Server Side Public License, v 1; you may not use this file except
+# in compliance with, at your election, the Elastic License 2.0 or the Server
+# Side Public License, v 1.
+#
+
+# The whitelist for the fields api
+
+# The scripts must be whitelisted for painless to find the classes for the field API
+class org.elasticsearch.script.AggregationScript @no_import {
+}
+class org.elasticsearch.script.AggregationScript$Factory @no_import {
+}

modules/lang-painless/src/main/resources/org/elasticsearch/painless/org.elasticsearch.script.fields.field.txt

@@ -0,0 +1,15 @@
+#
+# Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+# or more contributor license agreements. Licensed under the Elastic License
+# 2.0 and the Server Side Public License, v 1; you may not use this file except
+# in compliance with, at your election, the Elastic License 2.0 or the Server
+# Side Public License, v 1.
+#
+
+# The whitelist for the fields api
+
+# The scripts must be whitelisted for painless to find the classes for the field API
+class org.elasticsearch.script.FieldScript @no_import {
+}
+class org.elasticsearch.script.FieldScript @no_import {
+}

modules/lang-painless/src/yamlRestTest/resources/rest-api-spec/test/painless/100_terms_agg.yml

@@ -66,6 +66,24 @@ setup:
   - is_false: aggregations.str_terms.buckets.1.key_as_string
   - match: { aggregations.str_terms.buckets.1.doc_count: 1 }
 
+---
+"String Value Script with doc notation (fields api)":
+
+  - do:
+      search:
+        rest_total_hits_as_int: true
+        body: { "size" : 0, "aggs" : { "str_terms" : { "terms" : { "field" : "str", "script": { "source": "return field('str').getValue('') + \"1\""} } } } }
+
+  - match: { hits.total: 3 }
+
+  - length: { aggregations.str_terms.buckets: 2 }
+  - match: { aggregations.str_terms.buckets.0.key: "abc1" }
+  - is_false: aggregations.str_terms.buckets.0.key_as_string
+  - match: { aggregations.str_terms.buckets.0.doc_count: 2 }
+  - match: { aggregations.str_terms.buckets.1.key: "bcd1" }
+  - is_false: aggregations.str_terms.buckets.1.key_as_string
+  - match: { aggregations.str_terms.buckets.1.doc_count: 1 }
+
 ---
 "Long Value Script with doc notation":
 
@@ -84,6 +102,24 @@ setup:
   - is_false: aggregations.long_terms.buckets.1.key_as_string
   - match: { aggregations.long_terms.buckets.1.doc_count: 1 }
 
+---
+"Long Value Script with doc notation (fields api)":
+
+  - do:
+      search:
+        rest_total_hits_as_int: true
+        body: { "size" : 0, "aggs" : { "long_terms" : { "terms" : { "field" : "number", "script": { "source": "return field('number').getValue(0L) + 1"} } } } }
+
+  - match: { hits.total: 3 }
+
+  - length: { aggregations.long_terms.buckets: 2 }
+  - match: { aggregations.long_terms.buckets.0.key: 2.0 }
+  - is_false: aggregations.long_terms.buckets.0.key_as_string
+  - match: { aggregations.long_terms.buckets.0.doc_count: 2 }
+  - match: { aggregations.long_terms.buckets.1.key: 3.0 }
+  - is_false: aggregations.long_terms.buckets.1.key_as_string
+  - match: { aggregations.long_terms.buckets.1.doc_count: 1 }
+
 ---
 "Double Value Script with doc notation":
 
@@ -102,6 +138,24 @@ setup:
   - is_false: aggregations.double_terms.buckets.1.key_as_string
   - match: { aggregations.double_terms.buckets.1.doc_count: 1 }
 
+---
+"Double Value Script with doc notation (fields api)":
+
+  - do:
+      search:
+        rest_total_hits_as_int: true
+        body: { "size" : 0, "aggs" : { "double_terms" : { "terms" : { "field" : "double", "script": { "source": "return field('double').getValue(0.0) + 1"} } } } }
+
+  - match: { hits.total: 3 }
+
+  - length: { aggregations.double_terms.buckets: 2 }
+  - match: { aggregations.double_terms.buckets.0.key: 2.0 }
+  - is_false: aggregations.double_terms.buckets.0.key_as_string
+  - match: { aggregations.double_terms.buckets.0.doc_count: 2 }
+  - match: { aggregations.double_terms.buckets.1.key: 3.0 }
+  - is_false: aggregations.double_terms.buckets.1.key_as_string
+  - match: { aggregations.double_terms.buckets.1.doc_count: 1 }
+
 ---
 "Bucket script with keys":
 

modules/lang-painless/src/yamlRestTest/resources/rest-api-spec/test/painless/130_metric_agg.yml

@@ -0,0 +1,85 @@
+setup:
+  - do:
+      indices.create:
+        index: test
+        body:
+          settings:
+            number_of_replicas: 0
+          mappings:
+            properties:
+              double:
+                type: double
+
+  - do:
+      cluster.health:
+        wait_for_status: green
+
+  - do:
+      index:
+        index: test
+        id: 1
+        body:
+          double: 1.0
+
+  - do:
+      index:
+        index: test
+        id: 2
+        body:
+          double: 1.0
+
+  - do:
+      index:
+        index: test
+        id: 3
+        body:
+          double: 2.0
+
+  - do:
+      indices.refresh: {}
+
+---
+"Scripted Metric Agg Total":
+
+  - do:
+      search:
+        rest_total_hits_as_int: true
+        body: {
+          "size": 0,
+          "aggs": {
+            "total": {
+              "scripted_metric": {
+                "init_script": "state.transactions = []",
+                "map_script": "state.transactions.add(doc['double'].value)",
+                "combine_script": "double total = 0.0; for (t in state.transactions) { total += t } return total",
+                "reduce_script": "double total = 0; for (a in states) { total += a } return total"
+              }
+            }
+          }
+        }
+
+  - match: { hits.total: 3 }
+  - match: { aggregations.total.value: 4.0 }
+
+---
+"Scripted Metric Agg Total (fields api)":
+
+  - do:
+      search:
+        rest_total_hits_as_int: true
+        body: {
+          "size": 0,
+          "aggs": {
+            "total": {
+              "scripted_metric": {
+                "init_script": "state.transactions = []",
+                "map_script": "state.transactions.add(field('double').getValue(0.0))",
+                "combine_script": "double total = 0.0; for (t in state.transactions) { total += t } return total",
+                "reduce_script": "double total = 0; for (a in states) { total += a } return total"
+              }
+            }
+          }
+        }
+
+  - match: { hits.total: 3 }
+  - match: { aggregations.total.value: 4.0 }

modules/lang-painless/src/yamlRestTest/resources/rest-api-spec/test/painless/20_scriptfield.yml

@@ -44,6 +44,21 @@ setup:
 
     - match: { hits.hits.0.fields.bar.0: "aaabbb"}
 
+---
+"Scripted Field (fields api)":
+  - do:
+      search:
+        rest_total_hits_as_int: true
+        body:
+          script_fields:
+            bar:
+              script:
+                source: "field('foo').getValue('') + params.x;"
+                params:
+                  x: "bbb"
+
+  - match: { hits.hits.0.fields.bar.0: "aaabbb"}
+
 ---
 "Scripted Field Doing Compare":
     - do:
@@ -73,6 +88,35 @@ setup:
 
     - match: { hits.hits.0.fields.bar.0: false}
 
+---
+"Scripted Field Doing Compare (fields api)":
+  - do:
+      search:
+        rest_total_hits_as_int: true
+        body:
+          script_fields:
+            bar:
+              script:
+                source: "boolean compare(Supplier s, def v) {return s.get() == v;}
+                                     compare(() -> { return field('foo').getValue('') }, params.x);"
+                params:
+                  x: "aaa"
+
+  - match: { hits.hits.0.fields.bar.0: true}
+  - do:
+      search:
+        rest_total_hits_as_int: true
+        body:
+          script_fields:
+            bar:
+              script:
+                source: "boolean compare(Supplier s, def v) {return s.get() == v;}
+                                     compare(() -> { return doc['foo'].value }, params.x);"
+                params:
+                  x: "bbb"
+
+  - match: { hits.hits.0.fields.bar.0: false}
+
 ---
 "Scripted Field with a null safe dereference (non-null)":
     - do:
@@ -116,6 +160,19 @@ setup:
 
     - match: { hits.hits.0.fields.bar.0: 7}
 
+---
+"Access a date (fields api)":
+  - do:
+      search:
+        rest_total_hits_as_int: true
+        body:
+          script_fields:
+            bar:
+              script:
+                source: "field('date').getValue(new Date()).dayOfWeekEnum.value"
+
+  - match: { hits.hits.0.fields.bar.0: 7}
+
 ---
 "Access many dates":
     - do:
@@ -134,6 +191,24 @@ setup:
 
     - match: { hits.hits.0.fields.bar.0: "7 3 3"}
 
+---
+"Access many dates (fields api)":
+  - do:
+      search:
+        rest_total_hits_as_int: true
+        body:
+          script_fields:
+            bar:
+              script:
+                source: >
+                  StringBuilder b = new StringBuilder();
+                  for (def date : field('dates').getValues()) {
+                    b.append(" ").append(date.getDayOfWeekEnum().value);
+                  }
+                  return b.toString().trim()
+
+  - match: { hits.hits.0.fields.bar.0: "7 3 3"}
+
 ---
 "Scripted Field with script error":
     - do: