HLRC - add support for source exists API (#34904)

HLRC - add support for source exists API
API re-uses the GetRequest object (following the precedent set by the plain “exists” api).
Backport of #34519

client/rest-high-level/src/main/java/org/elasticsearch/client/RequestConverters.java

@@ -268,6 +268,18 @@ private static Request getStyleRequest(String method, GetRequest getRequest) {
 
         return request;
     }
+
+    static Request sourceExists(GetRequest getRequest) {
+        Request request = new Request(HttpHead.METHOD_NAME, endpoint(getRequest.index(), getRequest.type(), getRequest.id(), "_source"));
+
+        Params parameters = new Params(request);
+        parameters.withPreference(getRequest.preference());
+        parameters.withRouting(getRequest.routing());
+        parameters.withRefresh(getRequest.refresh());
+        parameters.withRealtime(getRequest.realtime());
+        // Version params are not currently supported by the source exists API so are not passed
+        return request;
+    }    
 
     static Request multiGet(MultiGetRequest multiGetRequest) throws IOException {
         Request request = new Request(HttpPost.METHOD_NAME, "/_mget");

client/rest-high-level/src/main/java/org/elasticsearch/client/RestHighLevelClient.java

@@ -837,6 +837,32 @@ public final void existsAsync(GetRequest getRequest, ActionListener<Boolean> lis
                 emptySet(), headers);
     }
 
+    /**
+     * Checks for the existence of a document with a "_source" field. Returns true if it exists, false otherwise.
+     * See <a href="https://www.elastic.co/guide/en/elasticsearch/reference/current/docs-get.html#_source">Source exists API 
+     * on elastic.co</a>
+     * @param getRequest the request
+     * @param options the request options (e.g. headers), use {@link RequestOptions#DEFAULT} if nothing needs to be customized
+     * @return <code>true</code> if the document and _source field exists, <code>false</code> otherwise
+     * @throws IOException in case there is a problem sending the request
+     */
+    public boolean existsSource(GetRequest getRequest, RequestOptions options) throws IOException {
+        return performRequest(getRequest, RequestConverters::sourceExists, options, RestHighLevelClient::convertExistsResponse, emptySet());
+    }     
+
+    /**
+     * Asynchronously checks for the existence of a document with a "_source" field. Returns true if it exists, false otherwise.
+     * See <a href="https://www.elastic.co/guide/en/elasticsearch/reference/current/docs-get.html#_source">Source exists API 
+     * on elastic.co</a>
+     * @param getRequest the request
+     * @param options the request options (e.g. headers), use {@link RequestOptions#DEFAULT} if nothing needs to be customized
+     * @param listener the listener to be notified upon request completion
+     */
+    public final void existsSourceAsync(GetRequest getRequest, RequestOptions options, ActionListener<Boolean> listener) {
+        performRequestAsync(getRequest, RequestConverters::sourceExists, options, RestHighLevelClient::convertExistsResponse, listener,
+                emptySet());
+    }    
+
     /**
      * Index a document using the Index API.
      * See <a href="https://www.elastic.co/guide/en/elasticsearch/reference/current/docs-index_.html">Index API on elastic.co</a>

client/rest-high-level/src/test/java/org/elasticsearch/client/CrudIT.java

@@ -204,6 +204,61 @@ public void testExists() throws IOException {
                     highLevelClient()::exists, highLevelClient()::existsAsync));
         }
     }
+
+    public void testSourceExists() throws IOException {     
+        {
+            GetRequest getRequest = new GetRequest("index", "type", "id");
+            assertFalse(execute(getRequest, highLevelClient()::existsSource, highLevelClient()::existsSourceAsync));
+        }
+        IndexRequest index = new IndexRequest("index", "type", "id");
+        index.source("{\"field1\":\"value1\",\"field2\":\"value2\"}", XContentType.JSON);
+        index.setRefreshPolicy(RefreshPolicy.IMMEDIATE);
+        highLevelClient().index(index, RequestOptions.DEFAULT);
+        {
+            GetRequest getRequest = new GetRequest("index", "type", "id");
+            assertTrue(execute(getRequest, highLevelClient()::existsSource, highLevelClient()::existsSourceAsync));
+        }
+        {
+            GetRequest getRequest = new GetRequest("index", "type", "does_not_exist");
+            assertFalse(execute(getRequest, highLevelClient()::existsSource, highLevelClient()::existsSourceAsync));
+        }
+        {
+            GetRequest getRequest = new GetRequest("index", "type", "does_not_exist").version(1);
+            assertFalse(execute(getRequest, highLevelClient()::existsSource, highLevelClient()::existsSourceAsync));
+        }
+    }
+
+    public void testSourceDoesNotExist() throws IOException {     
+        final String noSourceIndex = "no_source";
+        {
+            // Prepare
+            Settings settings = Settings.builder()
+                .put("number_of_shards", 1)
+                .put("number_of_replicas", 0)
+                .build();
+            String mapping = "\"_doc\": { \"_source\": {\n" + 
+                    "        \"enabled\": false\n" + 
+                    "      }  }";
+            createIndex(noSourceIndex, settings, mapping);
+            assertEquals(
+                RestStatus.OK,
+                highLevelClient().bulk(
+                    new BulkRequest()
+                        .add(new IndexRequest(noSourceIndex, "_doc", "1")
+                            .source(Collections.singletonMap("foo", 1), XContentType.JSON))
+                        .add(new IndexRequest(noSourceIndex, "_doc", "2")
+                            .source(Collections.singletonMap("foo", 2), XContentType.JSON))
+                        .setRefreshPolicy(RefreshPolicy.IMMEDIATE),
+                    RequestOptions.DEFAULT
+                ).status()
+            );
+        }        
+        {
+            GetRequest getRequest = new GetRequest(noSourceIndex, "_doc", "1");
+            assertTrue(execute(getRequest, highLevelClient()::exists, highLevelClient()::existsAsync));
+            assertFalse(execute(getRequest, highLevelClient()::existsSource, highLevelClient()::existsSourceAsync));
+        }
+    }    
 
     public void testGet() throws IOException {
         {

client/rest-high-level/src/test/java/org/elasticsearch/client/RestHighLevelClientTests.java

@@ -666,7 +666,6 @@ public void testApiNamingConventions() throws Exception {
             "cluster.remote_info",
             "count",
             "create",
-            "exists_source",
             "get_source",
             "indices.delete_alias",
             "indices.delete_template",

docs/java-rest/high-level/document/exists.asciidoc

@@ -29,3 +29,10 @@ include-tagged::{doc-tests-file}[{api}-request]
 <5> Disable fetching stored fields.
 
 include::../execution.asciidoc[]
+
+
+==== Source exists request
+A variant of the exists request is `existsSource` method which has the additional check
+that the document in question has stored the `source`. If the mapping for the index has opted
+to remove support for storing JSON source in documents then this method will return false
+for documents in this index.