Merge pull request #19595 from cbuescher/fix-19422

Allow empty json object in request body in `_count` API.

core/src/main/java/org/elasticsearch/index/query/QueryParseContext.java

@@ -73,9 +73,6 @@ public class QueryParseContext implements ParseFieldMatcherSupplier {
                     }
                 }
             }
-            if (queryBuilder == null) {
-                throw new ParsingException(parser.getTokenLocation(), "Required query is missing");
-            }
             return queryBuilder;
         } catch (ParsingException e) {
             throw e;
@@ -113,7 +110,7 @@ public class QueryParseContext implements ParseFieldMatcherSupplier {
         // move to the next START_OBJECT
         token = parser.nextToken();
         if (token != XContentParser.Token.START_OBJECT && token != XContentParser.Token.START_ARRAY) {
-            throw new ParsingException(parser.getTokenLocation(), "[_na] query malformed, no field after start_object");
+            throw new ParsingException(parser.getTokenLocation(), "[_na] query malformed, no start_object after query name");
         }
         @SuppressWarnings("unchecked")
         Optional<QueryBuilder> result = (Optional<QueryBuilder>) indicesQueriesRegistry.lookup(queryName, parseFieldMatcher,

core/src/test/java/org/elasticsearch/index/query/QueryParseContextTests.java

@@ -0,0 +1,128 @@
+/*
+ * Licensed to Elasticsearch under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch licenses this file to you under
+ * the Apache License, Version 2.0 (the "License"); you may
+ * not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package org.elasticsearch.index.query;
+
+import org.elasticsearch.common.ParseFieldMatcher;
+import org.elasticsearch.common.ParsingException;
+import org.elasticsearch.common.io.stream.NamedWriteableRegistry;
+import org.elasticsearch.common.settings.Settings;
+import org.elasticsearch.common.xcontent.XContentFactory;
+import org.elasticsearch.common.xcontent.XContentParser;
+import org.elasticsearch.common.xcontent.json.JsonXContent;
+import org.elasticsearch.indices.query.IndicesQueriesRegistry;
+import org.elasticsearch.search.SearchModule;
+import org.elasticsearch.test.ESTestCase;
+import org.junit.BeforeClass;
+
+import java.io.IOException;
+import java.util.Optional;
+
+import static java.util.Collections.emptyList;
+
+public class QueryParseContextTests extends ESTestCase {
+
+    private static IndicesQueriesRegistry indicesQueriesRegistry;
+
+    @BeforeClass
+    public static void init() {
+        indicesQueriesRegistry = new SearchModule(Settings.EMPTY, new NamedWriteableRegistry(), false, emptyList())
+                .getQueryParserRegistry();
+    }
+
+    public void testParseTopLevelBuilder() throws IOException {
+        QueryBuilder query = new MatchQueryBuilder("foo", "bar");
+        String requestBody = "{ \"query\" : " + query.toString() + "}";
+        try (XContentParser parser = XContentFactory.xContent(requestBody).createParser(requestBody)) {
+            QueryParseContext context = new QueryParseContext(indicesQueriesRegistry, parser, ParseFieldMatcher.STRICT);
+            QueryBuilder actual = context.parseTopLevelQueryBuilder();
+            assertEquals(query, actual);
+        }
+    }
+
+    public void testParseTopLevelBuilderEmptyObject() throws IOException {
+        String requestBody = "{}";
+        try (XContentParser parser = XContentFactory.xContent(requestBody).createParser(requestBody)) {
+            QueryParseContext context = new QueryParseContext(indicesQueriesRegistry, parser, ParseFieldMatcher.STRICT);
+            QueryBuilder query = context.parseTopLevelQueryBuilder();
+            assertNull(query);
+        }
+    }
+
+    public void testParseTopLevelBuilderUnknownParameter() throws IOException {
+        String requestBody = "{ \"foo\" : \"bar\"}";
+        try (XContentParser parser = XContentFactory.xContent(requestBody).createParser(requestBody)) {
+            QueryParseContext context = new QueryParseContext(indicesQueriesRegistry, parser, ParseFieldMatcher.STRICT);
+            ParsingException exception = expectThrows(ParsingException.class, () ->  context.parseTopLevelQueryBuilder());
+            assertEquals("request does not support [foo]", exception.getMessage());
+        }
+    }
+
+    public void testParseInnerQueryBuilder() throws IOException {
+        QueryBuilder query = new MatchQueryBuilder("foo", "bar");
+        String source = query.toString();
+        try (XContentParser parser = XContentFactory.xContent(source).createParser(source)) {
+            QueryParseContext context = new QueryParseContext(indicesQueriesRegistry, parser, ParseFieldMatcher.STRICT);
+            Optional<QueryBuilder> actual = context.parseInnerQueryBuilder();
+            assertEquals(query, actual.get());
+        }
+    }
+
+    public void testParseInnerQueryBuilderEmptyBody() throws IOException {
+        String source = "{}";
+        try (XContentParser parser = XContentFactory.xContent(source).createParser(source)) {
+            QueryParseContext context = new QueryParseContext(indicesQueriesRegistry, parser, ParseFieldMatcher.EMPTY);
+            Optional<QueryBuilder> emptyQuery = context.parseInnerQueryBuilder();
+            assertFalse(emptyQuery.isPresent());
+        }
+    }
+
+    public void testParseInnerQueryBuilderExceptions() throws IOException {
+        String source = "{ \"foo\": \"bar\" }";
+        try (XContentParser parser = JsonXContent.jsonXContent.createParser(source)) {
+            parser.nextToken();
+            parser.nextToken(); // don't start with START_OBJECT to provoke exception
+            QueryParseContext context = new QueryParseContext(indicesQueriesRegistry, parser, ParseFieldMatcher.STRICT);
+            ParsingException exception = expectThrows(ParsingException.class, () ->  context.parseInnerQueryBuilder());
+            assertEquals("[_na] query malformed, must start with start_object", exception.getMessage());
+        }
+
+        source = "{}";
+        try (XContentParser parser = JsonXContent.jsonXContent.createParser(source)) {
+            QueryParseContext context = new QueryParseContext(indicesQueriesRegistry, parser, ParseFieldMatcher.STRICT);
+            IllegalArgumentException exception = expectThrows(IllegalArgumentException.class, () ->  context.parseInnerQueryBuilder());
+            assertEquals("query malformed, empty clause found at [1:2]", exception.getMessage());
+        }
+
+        source = "{ \"foo\" : \"bar\" }";
+        try (XContentParser parser = JsonXContent.jsonXContent.createParser(source)) {
+            QueryParseContext context = new QueryParseContext(indicesQueriesRegistry, parser, ParseFieldMatcher.STRICT);
+            ParsingException exception = expectThrows(ParsingException.class, () ->  context.parseInnerQueryBuilder());
+            assertEquals("[_na] query malformed, no start_object after query name", exception.getMessage());
+        }
+
+        source = "{ \"foo\" : {} }";
+        try (XContentParser parser = JsonXContent.jsonXContent.createParser(source)) {
+            QueryParseContext context = new QueryParseContext(indicesQueriesRegistry, parser, ParseFieldMatcher.STRICT);
+            ParsingException exception = expectThrows(ParsingException.class, () ->  context.parseInnerQueryBuilder());
+            assertEquals("no [query] registered for [foo]", exception.getMessage());
+        }
+    }
+
+}

rest-api-spec/src/main/resources/rest-api-spec/test/count/10_basic.yaml

@@ -37,6 +37,24 @@ setup:
 
   - match: {count : 0}
 
+---
+"count with empty body":
+# empty body should default to match_all query
+  - do:
+      count:
+        index: test
+        type: test
+        body: { }
+
+  - match: {count : 1}
+
+  - do:
+      count:
+        index: test
+        type: test
+
+  - match: {count : 1}
+
 ---
 "count body without query element":
   - do: