MB-61216: Interpret empty query (in search request) as a match_none (…

…#2000)

search/query/query.go

@@ -98,11 +98,22 @@ func ParsePreSearchData(input []byte) (map[string]interface{}, error) {
 // ParseQuery deserializes a JSON representation of
 // a Query object.
 func ParseQuery(input []byte) (Query, error) {
+	if len(input) == 0 {
+		// interpret as a match_none query
+		return NewMatchNoneQuery(), nil
+	}
+
 	var tmp map[string]interface{}
 	err := util.UnmarshalJSON(input, &tmp)
 	if err != nil {
 		return nil, err
 	}
+
+	if len(tmp) == 0 {
+		// interpret as a match_none query
+		return NewMatchNoneQuery(), nil
+	}
+
 	_, hasFuzziness := tmp["fuzziness"]
 	_, isMatchQuery := tmp["match"]
 	_, isMatchPhraseQuery := tmp["match_phrase"]

search/query/query_test.go

@@ -763,3 +763,25 @@ func TestGeoShapeQuery(t *testing.T) {
 		}
 	}
 }
+
+func TestParseEmptyQuery(t *testing.T) {
+	var qBytes []byte
+	rv, err := ParseQuery(qBytes)
+	if err != nil {
+		t.Fatal(err)
+	}
+	expect := NewMatchNoneQuery()
+	if !reflect.DeepEqual(rv, expect) {
+		t.Errorf("[1] Expected %#v, got %#v", expect, rv)
+	}
+
+	qBytes = []byte(`{}`)
+	rv, err = ParseQuery(qBytes)
+	if err != nil {
+		t.Fatal(err)
+	}
+	expect = NewMatchNoneQuery()
+	if !reflect.DeepEqual(rv, expect) {
+		t.Errorf("[2] Expected %#v, got %#v", expect, rv)
+	}
+}