Do not treat 0 as boolean value in the REST controller

model/ConceptSearchParameters.php

@@ -65,10 +65,10 @@ public function getArrayClass()
         return null;
     }
 
-    public function getSearchTerm()
+    public function getSearchTerm() : string
     {
         $term = $this->request->getQueryParamRaw('q') ? $this->request->getQueryParamRaw('q') : $this->request->getQueryParamRaw('query');
-        if (!$term && $this->rest)
+        if ((!isset($term) || strlen(trim($term)) === 0) && $this->rest)
             $term = $this->request->getQueryParamRaw('label');
         $term = trim($term); // surrounding whitespace is not considered significant
         $term = Normalizer::normalize( $term, Normalizer::FORM_C ); //Normalize decomposed unicode characters #1184

tests/ConceptSearchParametersTest.php

@@ -86,6 +86,26 @@ public function testGetSearchTerm() {
         $this->assertEquals('test', $params->getSearchTerm());
     }
 
+    /**
+     * For https://github.com/NatLibFi/Skosmos/issues/1275, to verify
+     * that querying for `0` (zero) does not evaluate it as a boolean
+     * value, causing issues in the SKOSMOS search functionality.
+     *
+     * @covers ConceptSearchParameters::getSearchTerm
+     */
+    public function testGetSearchTermZeroes() {
+        $params = new ConceptSearchParameters($this->request, new GlobalConfig('/../tests/testconfig.ttl'), true);
+        $this->assertEquals('', $params->getSearchTerm());
+        $this->request->method('getQueryParamRaw')->will(
+            $this->returnValueMap([
+                ['q', '0'],
+                ['query', '0'],
+                ['label', '10']
+            ])
+        );
+        $this->assertEquals('0', $params->getSearchTerm());
+    }
+
     /**
      * @covers ConceptSearchParameters::getTypeLimit
      * @covers ConceptSearchParameters::getDefaultTypeLimit