Fix multi fields empty query (#33017)

This change fixes empty query removal when all fields remove the search term in
`simple_query_string`, `multi_match` and `query_string`.

Closes #33009

server/src/main/java/org/elasticsearch/index/query/QueryStringQueryBuilder.java

@@ -328,8 +328,9 @@ public class QueryStringQueryBuilder extends AbstractQueryBuilder<QueryStringQue
     /**
      * @param type Sets how multiple fields should be combined to build textual part queries.
      */
-    public void type(MultiMatchQueryBuilder.Type type) {
+    public QueryStringQueryBuilder type(MultiMatchQueryBuilder.Type type) {
         this.type = type;
+        return this;
     }
 
     /**

server/src/main/java/org/elasticsearch/index/search/MultiMatchQuery.java

@@ -120,7 +120,7 @@ public class MultiMatchQuery extends MatchQuery {
 
         private Query combineGrouped(List<? extends Query> groupQuery) {
             if (groupQuery == null || groupQuery.isEmpty()) {
-                return  new MatchNoDocsQuery("[multi_match] list of group queries was empty");
+                return zeroTermsQuery();
             }
             if (groupQuery.size() == 1) {
                 return groupQuery.get(0);

server/src/main/java/org/elasticsearch/index/search/QueryStringQueryParser.java

@@ -347,6 +347,9 @@ public class QueryStringQueryParser extends XQueryParser {
             }
             queryBuilder.setPhraseSlop(slop);
             Query query = queryBuilder.parse(MultiMatchQueryBuilder.Type.PHRASE, fields, queryText, null);
+            if (query == null) {
+                return null;
+            }
             return applySlop(query, slop);
         } catch (IOException e) {
             throw new ParseException(e.getMessage());

server/src/test/java/org/elasticsearch/index/query/MultiMatchQueryBuilderTests.java

@@ -21,6 +21,7 @@ package org.elasticsearch.index.query;
 
 import org.apache.lucene.index.Term;
 import org.apache.lucene.queries.ExtendedCommonTermsQuery;
+import org.apache.lucene.search.BooleanClause;
 import org.apache.lucene.search.BooleanQuery;
 import org.apache.lucene.search.BoostQuery;
 import org.apache.lucene.search.DisjunctionMaxQuery;
@@ -381,6 +382,69 @@ public class MultiMatchQueryBuilderTests extends AbstractQueryTestCase<MultiMatc
         assertEquals(expected, query);
     }
 
+    public void testWithStopWords() throws Exception {
+        Query query = new MultiMatchQueryBuilder("the quick fox")
+            .field(STRING_FIELD_NAME)
+            .analyzer("stop")
+            .toQuery(createShardContext());
+        Query expected = new BooleanQuery.Builder()
+            .add(new TermQuery(new Term(STRING_FIELD_NAME, "quick")), BooleanClause.Occur.SHOULD)
+            .add(new TermQuery(new Term(STRING_FIELD_NAME, "fox")), BooleanClause.Occur.SHOULD)
+            .build();
+        assertEquals(expected, query);
+
+        query = new MultiMatchQueryBuilder("the quick fox")
+            .field(STRING_FIELD_NAME)
+            .field(STRING_FIELD_NAME_2)
+            .analyzer("stop")
+            .toQuery(createShardContext());
+        expected = new DisjunctionMaxQuery(
+            Arrays.asList(
+                new BooleanQuery.Builder()
+                    .add(new TermQuery(new Term(STRING_FIELD_NAME, "quick")), BooleanClause.Occur.SHOULD)
+                    .add(new TermQuery(new Term(STRING_FIELD_NAME, "fox")), BooleanClause.Occur.SHOULD)
+                    .build(),
+                new BooleanQuery.Builder()
+                    .add(new TermQuery(new Term(STRING_FIELD_NAME_2, "quick")), BooleanClause.Occur.SHOULD)
+                    .add(new TermQuery(new Term(STRING_FIELD_NAME_2, "fox")), BooleanClause.Occur.SHOULD)
+                    .build()
+            ), 0f);
+        assertEquals(expected, query);
+
+        query = new MultiMatchQueryBuilder("the")
+            .field(STRING_FIELD_NAME)
+            .field(STRING_FIELD_NAME_2)
+            .analyzer("stop")
+            .toQuery(createShardContext());
+        expected = new DisjunctionMaxQuery(Arrays.asList(new MatchNoDocsQuery(), new MatchNoDocsQuery()), 0f);
+        assertEquals(expected, query);
+
+        query = new BoolQueryBuilder()
+            .should(
+                new MultiMatchQueryBuilder("the")
+                    .field(STRING_FIELD_NAME)
+                    .analyzer("stop")
+            )
+            .toQuery(createShardContext());
+        expected = new BooleanQuery.Builder()
+            .add(new MatchNoDocsQuery(), BooleanClause.Occur.SHOULD)
+            .build();
+        assertEquals(expected, query);
+
+        query = new BoolQueryBuilder()
+            .should(
+                new MultiMatchQueryBuilder("the")
+                    .field(STRING_FIELD_NAME)
+                    .field(STRING_FIELD_NAME_2)
+                    .analyzer("stop")
+            )
+            .toQuery(createShardContext());
+        expected = new BooleanQuery.Builder()
+            .add(new DisjunctionMaxQuery(Arrays.asList(new MatchNoDocsQuery(), new MatchNoDocsQuery()), 0f), BooleanClause.Occur.SHOULD)
+            .build();
+        assertEquals(expected, query);
+    }
+
     private static IndexMetaData newIndexMeta(String name, Settings oldIndexSettings, Settings indexSettings) {
         Settings build = Settings.builder().put(oldIndexSettings)
             .put(indexSettings)

server/src/test/java/org/elasticsearch/index/query/QueryStringQueryBuilderTests.java

@@ -1266,11 +1266,58 @@ public class QueryStringQueryBuilderTests extends AbstractQueryTestCase<QueryStr
             .field(STRING_FIELD_NAME)
             .analyzer("stop")
             .toQuery(createShardContext());
-        BooleanQuery expected = new BooleanQuery.Builder()
+        Query expected = new BooleanQuery.Builder()
+            .add(new TermQuery(new Term(STRING_FIELD_NAME, "quick")), BooleanClause.Occur.SHOULD)
+            .add(new TermQuery(new Term(STRING_FIELD_NAME, "fox")), BooleanClause.Occur.SHOULD)
+            .build();
+        assertEquals(expected, query);
+
+        query = new QueryStringQueryBuilder("the quick fox")
+            .field(STRING_FIELD_NAME)
+            .field(STRING_FIELD_NAME_2)
+            .analyzer("stop")
+            .toQuery(createShardContext());
+        expected = new DisjunctionMaxQuery(
+            Arrays.asList(
+                new BooleanQuery.Builder()
                     .add(new TermQuery(new Term(STRING_FIELD_NAME, "quick")), Occur.SHOULD)
                     .add(new TermQuery(new Term(STRING_FIELD_NAME, "fox")), Occur.SHOULD)
+                    .build(),
+                new BooleanQuery.Builder()
+                    .add(new TermQuery(new Term(STRING_FIELD_NAME_2, "quick")), Occur.SHOULD)
+                    .add(new TermQuery(new Term(STRING_FIELD_NAME_2, "fox")), Occur.SHOULD)
+                    .build()
+            ), 0f);
+        assertEquals(expected, query);
+
+        query = new QueryStringQueryBuilder("the")
+            .field(STRING_FIELD_NAME)
+            .field(STRING_FIELD_NAME_2)
+            .analyzer("stop")
+            .toQuery(createShardContext());
+        assertEquals(new BooleanQuery.Builder().build(), query);
+
+        query = new BoolQueryBuilder()
+            .should(
+                new QueryStringQueryBuilder("the")
+                    .field(STRING_FIELD_NAME)
+                    .analyzer("stop")
+            )
+            .toQuery(createShardContext());
+        expected = new BooleanQuery.Builder()
+            .add(new BooleanQuery.Builder().build(), BooleanClause.Occur.SHOULD)
             .build();
         assertEquals(expected, query);
+
+        query = new BoolQueryBuilder()
+            .should(
+                new QueryStringQueryBuilder("the")
+                    .field(STRING_FIELD_NAME)
+                    .field(STRING_FIELD_NAME_2)
+                    .analyzer("stop")
+            )
+            .toQuery(createShardContext());
+        assertEquals(expected, query);
     }
 
     public void testWithPrefixStopWords() throws Exception {

server/src/test/java/org/elasticsearch/index/query/SimpleQueryStringBuilderTests.java

@@ -613,11 +613,59 @@ public class SimpleQueryStringBuilderTests extends AbstractQueryTestCase<SimpleQ
             .field(STRING_FIELD_NAME)
             .analyzer("stop")
             .toQuery(createShardContext());
-        BooleanQuery expected = new BooleanQuery.Builder()
+        Query expected = new BooleanQuery.Builder()
             .add(new TermQuery(new Term(STRING_FIELD_NAME, "quick")), BooleanClause.Occur.SHOULD)
             .add(new TermQuery(new Term(STRING_FIELD_NAME, "fox")), BooleanClause.Occur.SHOULD)
             .build();
         assertEquals(expected, query);
+
+        query = new SimpleQueryStringBuilder("the quick fox")
+            .field(STRING_FIELD_NAME)
+            .field(STRING_FIELD_NAME_2)
+            .analyzer("stop")
+            .toQuery(createShardContext());
+        expected = new BooleanQuery.Builder()
+            .add(new DisjunctionMaxQuery(
+                Arrays.asList(
+                    new TermQuery(new Term(STRING_FIELD_NAME, "quick")),
+                    new TermQuery(new Term(STRING_FIELD_NAME_2, "quick"))
+                ), 1.0f), BooleanClause.Occur.SHOULD)
+            .add(new DisjunctionMaxQuery(
+                Arrays.asList(
+                    new TermQuery(new Term(STRING_FIELD_NAME, "fox")),
+                    new TermQuery(new Term(STRING_FIELD_NAME_2, "fox"))
+                ), 1.0f), BooleanClause.Occur.SHOULD)
+            .build();
+        assertEquals(expected, query);
+
+        query = new SimpleQueryStringBuilder("the")
+            .field(STRING_FIELD_NAME)
+            .field(STRING_FIELD_NAME_2)
+            .analyzer("stop")
+            .toQuery(createShardContext());
+        assertEquals(new MatchNoDocsQuery(), query);
+
+        query = new BoolQueryBuilder()
+            .should(
+                new SimpleQueryStringBuilder("the")
+                    .field(STRING_FIELD_NAME)
+                    .analyzer("stop")
+            )
+            .toQuery(createShardContext());
+        expected = new BooleanQuery.Builder()
+            .add(new MatchNoDocsQuery(), BooleanClause.Occur.SHOULD)
+            .build();
+        assertEquals(expected, query);
+
+        query = new BoolQueryBuilder()
+            .should(
+                new SimpleQueryStringBuilder("the")
+                    .field(STRING_FIELD_NAME)
+                    .field(STRING_FIELD_NAME_2)
+                    .analyzer("stop")
+            )
+            .toQuery(createShardContext());
+        assertEquals(expected, query);
     }
 
     public void testWithPrefixStopWords() throws Exception {