Workaround for operator minification bug.

module/VuFind/src/VuFind/Search/QueryAdapter.php

@@ -248,6 +248,13 @@ public static function minify(AbstractQuery $query, $topLevel = true)
                     'b' => $operator
                 ];
                 if (null !== ($op = $current->getOperator())) {
+                    // Some search forms omit the operator for the first element;
+                    // if we have an operator in a subsequent element, we should
+                    // backfill a blank here for consistency; otherwise, VuFind
+                    // may not construct correct search URLs.
+                    if (isset($retVal[0]['f']) && !isset($retVal[0]['o'])) {
+                        $retVal[0]['o'] = '';
+                    }
                     $currentArr['o'] = $op;
                 }
                 $retVal[] = $currentArr;

module/VuFind/tests/unit-tests/src/VuFindTest/Search/QueryAdapterTest.php

@@ -65,6 +65,36 @@ public function testConversions()
         }
     }
 
+    /**
+     * Test that when one part of the query contains an operator, ALL parts of the
+     * query contain an operator. (We want to be sure that in cases where the first
+     * part of the query has no operator associated with it, a blank value is filled
+     * in as a placeholder.
+     *
+     * @return void
+     */
+    public function testOperatorDefinedEverywhere()
+    {
+        $fixturePath = realpath(__DIR__ . '/../../../../fixtures/searches') . '/';
+        $q = unserialize(file_get_contents($fixturePath . '/operators'));
+        $minified = QueryAdapter::minify($q);
+
+        // First, check that count of 'o' values matches count of queries in group:
+        $callback = function ($carry, $item) {
+            return $carry + (isset($item['o']) ? 1 : 0);
+        };
+        $this->assertEquals(
+            count($minified[0]['g']),
+            array_reduce($minified[0]['g'], $callback, 0)
+        );
+
+        // Next, confirm that first operator is set to empty (filler) value:
+        $this->assertEquals('', $minified[0]['g'][0]['o']);
+
+        // Finally, make sure that we can round-trip back to the input.
+        $this->assertEquals($q, QueryAdapter::deminify($minified));
+    }
+
     /**
      * Test building an advanced query from a request.
      *