Switch pipeline agg parsing to ContextParser (#52776) (#52832)

We've pretty well settled on `ContextParser` for a generic interface to
`ObjectParser`-like-things. This switches the interface used for
building parsing pipeline aggregations to `ContextParser` which saves a
couple of little wrappers around `ObjectParser`.

server/src/main/java/org/elasticsearch/plugins/SearchPlugin.java

@@ -346,7 +346,8 @@ public interface SearchPlugin {
     /**
      * Specification for a {@link PipelineAggregator}.
      */
-    class PipelineAggregationSpec extends SearchExtensionSpec<PipelineAggregationBuilder, PipelineAggregator.Parser> {
+    class PipelineAggregationSpec extends SearchExtensionSpec<PipelineAggregationBuilder,
+            ContextParser<String, ? extends PipelineAggregationBuilder>> {
         private final Map<String, Writeable.Reader<? extends InternalAggregation>> resultReaders = new TreeMap<>();
         private final Writeable.Reader<? extends PipelineAggregator> aggregatorReader;
 
@@ -364,7 +365,7 @@ public interface SearchPlugin {
         public PipelineAggregationSpec(ParseField name,
                 Writeable.Reader<? extends PipelineAggregationBuilder> builderReader,
                 Writeable.Reader<? extends PipelineAggregator> aggregatorReader,
-                PipelineAggregator.Parser parser) {
+                ContextParser<String, ? extends PipelineAggregationBuilder> parser) {
             super(name, builderReader, parser);
             this.aggregatorReader = aggregatorReader;
         }
@@ -383,11 +384,52 @@ public interface SearchPlugin {
         public PipelineAggregationSpec(String name,
                 Writeable.Reader<? extends PipelineAggregationBuilder> builderReader,
                 Writeable.Reader<? extends PipelineAggregator> aggregatorReader,
-                PipelineAggregator.Parser parser) {
+                ContextParser<String, ? extends PipelineAggregationBuilder> parser) {
             super(name, builderReader, parser);
             this.aggregatorReader = aggregatorReader;
         }
 
+        /**
+         * Specification of a {@link PipelineAggregator}.
+         *
+         * @param name holds the names by which this aggregation might be parsed. The {@link ParseField#getPreferredName()} is special as it
+         *        is the name by under which the readers are registered. So it is the name that the {@link PipelineAggregationBuilder} and
+         *        {@link PipelineAggregator} should return from {@link NamedWriteable#getWriteableName()}.
+         * @param builderReader the reader registered for this aggregation's builder. Typically a reference to a constructor that takes a
+         *        {@link StreamInput}
+         * @param aggregatorReader reads the {@link PipelineAggregator} from a stream
+         * @param parser reads the aggregation builder from XContent
+         * @deprecated prefer the ctor that takes a {@link ContextParser}
+         */
+        @Deprecated
+        public PipelineAggregationSpec(ParseField name,
+                Writeable.Reader<? extends PipelineAggregationBuilder> builderReader,
+                Writeable.Reader<? extends PipelineAggregator> aggregatorReader,
+                PipelineAggregator.Parser parser) {
+            super(name, builderReader, (p, n) -> parser.parse(n, p));
+            this.aggregatorReader = aggregatorReader;
+        }
+
+        /**
+         * Specification of a {@link PipelineAggregator}.
+         *
+         * @param name name by which this aggregation might be parsed or deserialized. Make sure it is the name that the
+         *        {@link PipelineAggregationBuilder} and {@link PipelineAggregator} should return from
+         *        {@link NamedWriteable#getWriteableName()}.
+         * @param builderReader the reader registered for this aggregation's builder. Typically a reference to a constructor that takes a
+         *        {@link StreamInput}
+         * @param aggregatorReader reads the {@link PipelineAggregator} from a stream
+         * @deprecated prefer the ctor that takes a {@link ContextParser}
+         */
+        @Deprecated
+        public PipelineAggregationSpec(String name,
+                Writeable.Reader<? extends PipelineAggregationBuilder> builderReader,
+                Writeable.Reader<? extends PipelineAggregator> aggregatorReader,
+                PipelineAggregator.Parser parser) {
+            super(name, builderReader, (p, n) -> parser.parse(n, p));
+            this.aggregatorReader = aggregatorReader;
+        }
+
         /**
          * Add a reader for the shard level results of the aggregation with {@linkplain #getName()}'s {@link ParseField#getPreferredName()}
          * as the {@link NamedWriteable#getWriteableName()}.

server/src/main/java/org/elasticsearch/search/SearchModule.java

@@ -531,8 +531,9 @@ public class SearchModule {
                 MovAvgPipelineAggregationBuilder.NAME,
                 MovAvgPipelineAggregationBuilder::new,
                 MovAvgPipelineAggregator::new,
-                (n, c) -> MovAvgPipelineAggregationBuilder.parse(movingAverageModelParserRegistry, n, c))
+                (XContentParser parser, String name) ->
-                    /* Uses InternalHistogram for buckets */);
+                    MovAvgPipelineAggregationBuilder.parse(movingAverageModelParserRegistry, name, parser)
+                )/* Uses InternalHistogram for buckets */);
         registerPipelineAggregation(new PipelineAggregationSpec(
                 CumulativeSumPipelineAggregationBuilder.NAME,
                 CumulativeSumPipelineAggregationBuilder::new,
@@ -542,7 +543,7 @@ public class SearchModule {
                 BucketScriptPipelineAggregationBuilder.NAME,
                 BucketScriptPipelineAggregationBuilder::new,
                 BucketScriptPipelineAggregator::new,
-                (name, p) -> BucketScriptPipelineAggregationBuilder.PARSER.parse(p, name)));
+                BucketScriptPipelineAggregationBuilder.PARSER));
         registerPipelineAggregation(new PipelineAggregationSpec(
                 BucketSelectorPipelineAggregationBuilder.NAME,
                 BucketSelectorPipelineAggregationBuilder::new,
@@ -562,17 +563,15 @@ public class SearchModule {
                 MovFnPipelineAggregationBuilder.NAME,
                 MovFnPipelineAggregationBuilder::new,
                 MovFnPipelineAggregator::new,
-                (name, p) -> MovFnPipelineAggregationBuilder.PARSER.parse(p, name)));
+                MovFnPipelineAggregationBuilder.PARSER));
 
         registerFromPlugin(plugins, SearchPlugin::getPipelineAggregations, this::registerPipelineAggregation);
     }
 
     private void registerPipelineAggregation(PipelineAggregationSpec spec) {
         if (false == transportClient) {
-            namedXContents.add(new NamedXContentRegistry.Entry(BaseAggregationBuilder.class, spec.getName(), (p, c) -> {
+            namedXContents.add(new NamedXContentRegistry.Entry(BaseAggregationBuilder.class, spec.getName(),
-                String name = (String) c;
+                    (p, c) -> spec.getParser().parse(p, (String) c)));
-                return spec.getParser().parse(name, p);
-            }));
         }
         namedWriteables.add(
                 new NamedWriteableRegistry.Entry(PipelineAggregationBuilder.class, spec.getName().getPreferredName(), spec.getReader()));

x-pack/plugin/analytics/src/main/java/org/elasticsearch/xpack/analytics/AnalyticsPlugin.java

@@ -59,7 +59,7 @@ public class AnalyticsPlugin extends Plugin implements SearchPlugin, ActionPlugi
                 CumulativeCardinalityPipelineAggregationBuilder.NAME,
                 CumulativeCardinalityPipelineAggregationBuilder::new,
                 CumulativeCardinalityPipelineAggregator::new,
-                (name, p) -> CumulativeCardinalityPipelineAggregationBuilder.PARSER.parse(p, name))
+                CumulativeCardinalityPipelineAggregationBuilder.PARSER)
         );
     }