diff -u b/core/modules/views/src/Plugin/views/HandlerBase.php b/core/modules/views/src/Plugin/views/HandlerBase.php
--- b/core/modules/views/src/Plugin/views/HandlerBase.php
+++ b/core/modules/views/src/Plugin/views/HandlerBase.php
@@ -735,12 +735,12 @@
 
     // Determine if the string has 'or' operators (plus signs) or 'and'
     // operators (commas) and split the string accordingly.
-    if (preg_match(HandlerBase::generatePattern('+'), $str)) {
+    if (preg_match(HandlerBase::generatePattern('+', '+'), $str)) {
       // The '+' character in a query string may be parsed as ' '.
       $operator = 'or';
       $value = preg_split('/[+ ]/', $str);
     }
-    elseif (preg_match(HandlerBase::generatePattern(','), $str)) {
+    elseif (preg_match(HandlerBase::generatePattern(), $str)) {
       $operator = 'and';
       $value = explode(',', $str);
     }
@@ -875,10 +875,16 @@
   }
 
   /**
-   * Pass in a string to be added to an auto generated pattern.
+   * Pass in a string to be added to an auto generated pattern. That will be
+   * used to find patterns such as x,y,z and x+y+z.
+   *
+   * @param string $string
+   *   (Optional) A string to use for searching in the pattern. Defaults to ','.
+   * @param string $op
+   *   (Optional) A string used for searching what operation the regex pattern
+   *    will look for. Defaults to '*'.
    */
-  private static function generatePattern($string = ',') {
-    $op = ($string === ',') ? '*' : '+';
+  private static function generatePattern(string $string = ',', string $op = '*') {
     return '/^([\w0-9-_\.\#\&\/\(\)]+[' . $string . ' ]+)' . $op . '[\w0-9-_\.\#\&\/\(\)]+$/u';
   }