FEATURE: Support .simpleQueryStringFulltext() simple query string query for fulltext search

We want to support phrase searches like `"Neos and Flow"`, where
quotes mean "I want this exact phrase" (similar to many search engines).

When using the .fulltext() query, this did not work, and we sometimes
encountered crashes when the query string contained quotes, f.e. `"Hallo"`
or `Ha"llo"`.

This is because the .fulltext() query does some magic for supporting UTF8
(as it seems), namely: `trim(json_encode($searchWord, JSON_UNESCAPED_UNICODE), '"')`.
This removes some quotes, but not all of them :-)

The simple_query_string query of Elasticsearch exposes a query string syntax
which the user is directly allowed to enter:

> While its syntax is more limited than the query_string query, the simple_query_string
> query does not return errors for invalid syntax. Instead, it ignores any invalid
> parts of the query string.

This is exactly what we want for a good search field behavior.

NOTE: We created an additional method because we were unsure about breaking
      backwards compatibility; but we think `simpleQueryStringFulltext()` should
      be used almost universally as replacement for `fulltext()`, as it returns
      better results and does not throw exceptions..

Author: Katharina Puchstein

Classes/Driver/QueryInterface.php

@@ -81,6 +81,16 @@ public function from(int $size): void;
      */
     public function fulltext(string $searchWord, array $options = []): void;
 
+    /**
+     * Match the search word against the fulltext index using the elasticsearch
+     * [simple query string query](https://www.elastic.co/guide/en/elasticsearch/reference/current/query-dsl-simple-query-string-query.html)
+     *
+     * @param string $searchWord
+     * @param array $options Options to configure the query_string
+     * @return void
+     */
+    public function simpleQueryStringFulltext(string $searchWord, array $options = []): void;
+
     /**
      * Configure Result Highlighting. Only makes sense in combination with fulltext(). By default, highlighting is enabled.
      * It can be disabled by calling "highlight(FALSE)".

Classes/Driver/Version6/Query/FilteredQuery.php

@@ -67,6 +67,20 @@ public function fulltext(string $searchWord, array $options = []): void
         ]);
     }
 
+    /**
+     * {@inheritdoc}
+     */
+    public function simpleQueryStringFulltext(string $searchWord, array $options = []): void
+    {
+        $this->appendAtPath('query.bool.must', [
+            'simple_query_string' => array_merge(
+                $this->queryStringParameters,
+                $options,
+                [ 'query' => $searchWord ]
+            )
+        ]);
+    }
+
     /**
      * {@inheritdoc}
      */

Classes/Eel/ElasticSearchQueryBuilder.php

@@ -18,8 +18,6 @@
 use Flowpack\ElasticSearch\ContentRepositoryAdaptor\ElasticSearchClient;
 use Flowpack\ElasticSearch\ContentRepositoryAdaptor\Exception;
 use Flowpack\ElasticSearch\ContentRepositoryAdaptor\Exception\QueryBuildingException;
-use Flowpack\ElasticSearch\Domain\Model\Index;
-use Flowpack\ElasticSearch\Domain\Model\Mapping;
 use Neos\Flow\Log\ThrowableStorageInterface;
 use Neos\Flow\Log\Utility\LogEnvironment;
 use Neos\Flow\Persistence\Exception\IllegalObjectTypeException;
@@ -668,7 +666,9 @@ public function count(): int
     }
 
     /**
-     * Match the searchword against the fulltext index
+     * Match the searchword against the fulltext index.
+     *
+     * NOTE: Please use {@see simpleQueryStringFulltext} instead, as it is more robust.
      *
      * @param string $searchWord
      * @param array $options Options to configure the query_string, see https://www.elastic.co/guide/en/elasticsearch/reference/7.6/query-dsl-query-string-query.html
@@ -684,6 +684,32 @@ public function fulltext(string $searchWord, array $options = []): QueryBuilderI
         return $this;
     }
 
+    /**
+     * Match the searchword against the fulltext index using the elasticsearch
+     * [simple query string query](https://www.elastic.co/guide/en/elasticsearch/reference/current/query-dsl-simple-query-string-query.html).
+     *
+     * This method has two main benefits over {@see fulltext()}:
+     * - Supports phrase searches like `"Neos and Flow"`, where
+     *   quotes mean "I want this exact phrase" (similar to many search engines).
+     * - do not crash if the user does not enter a fully syntactically valid query
+     *   (invalid query parts are ignored).
+     *
+     * This is exactly what we want for a good search field behavior.
+     *
+     * @param string $searchWord
+     * @param array $options Options to configure the query_string, see https://www.elastic.co/guide/en/elasticsearch/reference/7.6/query-dsl-query-string-query.html
+     * @return QueryBuilderInterface
+     * @api
+     */
+    public function simpleQueryStringFulltext(string $searchWord, array $options = []): QueryBuilderInterface
+    {
+        // We automatically enable result highlighting when doing fulltext searches. It is up to the user to use this information or not use it.
+        $this->request->simpleQueryStringFulltext($searchWord, $options);
+        $this->request->highlight(150, 2);
+
+        return $this;
+    }
+
     /**
      * Adds a prefix filter to the query
      * See: https://www.elastic.co/guide/en/elasticsearch/reference/7.6/query-dsl-prefix-query.html

Configuration/Settings.yaml

@@ -50,7 +50,7 @@ Flowpack:
                   - 'aggregations'
                   - 'suggest'
 
-                # Parameters for the query string query used by the fullText() operation
+                # Parameters for the query string query used by the fullText() and simpleQueryStringFulltext() operation
                 # See https://www.elastic.co/guide/en/elasticsearch/reference/current/query-dsl-query-string-query.html#query-string-multi-field
                 # for all available parameters
                 queryStringParameters: