Remove support for types field in watcher search (elastic#120748)

In 8.x, setting the `input.search.request.types` field in the payload
when creating a watcher to an empty array was allowed, although it
resulted in a deprecation warning and had no effect (and any value
other than an empty array would result in an error).

In 9.x, support for this field is entirely removed, and the empty
array will also result in an error.

We have already introduced a script to be run as part of the upgrade
which removes the field from existing watches in
elastic#120371.

This also removes an unrelated TODO in passing, because we are not
going to do that (the functionality it refers to exists and is not
deprecated so cannot be removed).

ES-9747 #close #comment Types in search request removed in elastic#120748

Author: PeteGillinElastic

docs/changelog/120748.yaml

@@ -0,0 +1,15 @@
+pr: 120748
+summary: Removing support for types field in watcher search
+area: Watcher
+type: breaking
+issues: []
+breaking:
+  title: Removing support for types field in watcher search
+  area: REST API
+  details: >-
+    Previously, setting the `input.search.request.types` field in the payload when creating a watcher to an empty array
+    was  allowed, although it resulted in a deprecation warning and had no effect (and any value other than an empty
+    array would result in an error). Now, support for this field is entirely removed, and the empty array will also
+    result in an error.
+  impact: Users should stop setting this field (which did not have any effect anyway).
+  notable: false

x-pack/plugin/watcher/src/main/java/org/elasticsearch/xpack/watcher/support/search/WatcherSearchTemplateRequest.java

@@ -12,7 +12,6 @@
 import org.elasticsearch.common.Strings;
 import org.elasticsearch.common.bytes.BytesArray;
 import org.elasticsearch.common.bytes.BytesReference;
-import org.elasticsearch.common.logging.DeprecationCategory;
 import org.elasticsearch.common.logging.DeprecationLogger;
 import org.elasticsearch.core.Nullable;
 import org.elasticsearch.script.Script;
@@ -173,7 +172,6 @@ public static WatcherSearchTemplateRequest fromXContent(XContentParser parser, S
         IndicesOptions indicesOptions = DEFAULT_INDICES_OPTIONS;
         BytesReference searchSource = null;
         Script template = null;
-        // TODO this is to retain BWC compatibility in 7.0 and can be removed for 8.0
         boolean totalHitsAsInt = true;
 
         XContentParser.Token token;
@@ -196,17 +194,6 @@ public static WatcherSearchTemplateRequest fromXContent(XContentParser parser, S
                             );
                         }
                     }
-                } else if (TYPES_FIELD.match(currentFieldName, parser.getDeprecationHandler())) {
-                    // Tolerate an empty types array, because some watches created internally in 6.x have
-                    // an empty types array in their search, and it's clearly equivalent to typeless.
-                    if (parser.nextToken() != XContentParser.Token.END_ARRAY) {
-                        throw new ElasticsearchParseException(
-                            "could not read search request. unsupported non-empty array field [" + currentFieldName + "]"
-                        );
-                    }
-                    // Empty types arrays still generate the same deprecation warning they did in 7.x.
-                    // Ideally they should be removed from the definition.
-                    deprecationLogger.critical(DeprecationCategory.PARSING, "watcher_search_input", TYPES_DEPRECATION_MESSAGE);
                 } else {
                     throw new ElasticsearchParseException(
                         "could not read search request. unexpected array field [" + currentFieldName + "]"
@@ -289,7 +276,6 @@ public int hashCode() {
     }
 
     private static final ParseField INDICES_FIELD = new ParseField("indices");
-    private static final ParseField TYPES_FIELD = new ParseField("types");
     private static final ParseField BODY_FIELD = new ParseField("body");
     private static final ParseField SEARCH_TYPE_FIELD = new ParseField("search_type");
     private static final ParseField INDICES_OPTIONS_FIELD = new ParseField("indices_options");

x-pack/plugin/watcher/src/test/java/org/elasticsearch/xpack/watcher/support/search/WatcherSearchTemplateRequestTests.java

@@ -17,7 +17,6 @@
 import java.util.Map;
 
 import static java.util.Collections.singletonMap;
-import static org.hamcrest.Matchers.arrayContaining;
 import static org.hamcrest.Matchers.equalTo;
 import static org.hamcrest.Matchers.is;
 
@@ -52,8 +51,11 @@ public void testFromXContentWithEmptyTypes() throws IOException {
             """;
         try (XContentParser parser = createParser(JsonXContent.jsonXContent, source)) {
             parser.nextToken();
-            WatcherSearchTemplateRequest result = WatcherSearchTemplateRequest.fromXContent(parser, randomFrom(SearchType.values()));
-            assertThat(result.getIndices(), arrayContaining(".ml-anomalies-*"));
+            ElasticsearchParseException e = expectThrows(
+                ElasticsearchParseException.class,
+                () -> WatcherSearchTemplateRequest.fromXContent(parser, randomFrom(SearchType.values()))
+            );
+            assertThat(e.getMessage(), is("could not read search request. unexpected array field [types]"));
         }
     }
 
@@ -74,7 +76,7 @@ public void testFromXContentWithNonEmptyTypes() throws IOException {
                 ElasticsearchParseException.class,
                 () -> WatcherSearchTemplateRequest.fromXContent(parser, randomFrom(SearchType.values()))
             );
-            assertThat(e.getMessage(), is("could not read search request. unsupported non-empty array field [types]"));
+            assertThat(e.getMessage(), is("could not read search request. unexpected array field [types]"));
         }
     }