Initial test on loadSavedMapping function.

To facilitate this I
1) made it public - in the end it will go anyway
2) removed a 'pass-through' variable from the return array - it is passed in & returned unchanged
3) made it cope without a notice when a class property is not defined - that will go too soon

CRM/Contact/Import/Form/MapField.php

@@ -401,7 +401,7 @@ public function buildQuickForm() {
       $sel = &$this->addElement('hierselect', "mapper[$i]", ts('Mapper for Field %1', [1 => $i]), NULL);
 
       if ($this->get('savedMapping')) {
-        list($mappingName, $defaults, $js) = $this->loadSavedMapping($mappingName, $i, $mappingRelation, $mappingWebsiteType, $mappingLocation, $mappingPhoneType, $mappingImProvider, $defaults, $formName, $js, $hasColumnNames, $dataPatterns, $columnPatterns);
+        list($defaults, $js) = $this->loadSavedMapping($mappingName, $i, $mappingRelation, $mappingWebsiteType, $mappingLocation, $mappingPhoneType, $mappingImProvider, $defaults, $formName, $js, $hasColumnNames, $dataPatterns, $columnPatterns);
       }
       else {
         $js .= "swapOptions($formName, 'mapper[$i]', 0, 3, 'hs_mapper_0_');\n";
@@ -856,7 +856,7 @@ protected function saveMappingField($mapperKeys, array $saveMapping, string $cTy
    *
    * @return array
    */
-  protected function loadSavedMapping($mappingName, $i, $mappingRelation, $mappingWebsiteType, $mappingLocation, $mappingPhoneType, $mappingImProvider, $defaults, $formName, $js, $hasColumnNames, $dataPatterns, $columnPatterns) {
+  public function loadSavedMapping($mappingName, $i, $mappingRelation, $mappingWebsiteType, $mappingLocation, $mappingPhoneType, $mappingImProvider, $defaults, $formName, $js, $hasColumnNames, $dataPatterns, $columnPatterns) {
     $jsSet = FALSE;
     if (isset($mappingName[$i])) {
       if ($mappingName[$i] != ts('- do not import -')) {
@@ -935,7 +935,7 @@ protected function loadSavedMapping($mappingName, $i, $mappingRelation, $mapping
           $jsSet = TRUE;
         }
         else {
-          $mappingHeader = array_keys($this->_mapperFields, $mappingName[$i]);
+          $mappingHeader = array_keys((array) $this->_mapperFields, $mappingName[$i]);
           $websiteTypeId = isset($mappingWebsiteType[$i]) ? $mappingWebsiteType[$i] : NULL;
           $locationId = isset($mappingLocation[$i]) ? $mappingLocation[$i] : 0;
           $phoneType = isset($mappingPhoneType[$i]) ? $mappingPhoneType[$i] : NULL;
@@ -989,7 +989,7 @@ protected function loadSavedMapping($mappingName, $i, $mappingRelation, $mapping
         $defaults["mapper[$i]"] = [$this->defaultFromData($dataPatterns, $i)];
       }
     }
-    return [$mappingName, $defaults, $js];
+    return [$defaults, $js];
   }
 
 }

tests/phpunit/CRM/Contact/Import/Form/MapFieldTest.php

@@ -149,4 +149,77 @@ public function getFormObject($class, $formValues = [], $pageName = '') {
     return $form;
   }
 
+  /**
+   * Test the function that loads saved field mappings.
+   *
+   * @dataProvider mapFieldDataProvider
+   *
+   * @param array $fieldSpec
+   * @param string $expectedJS
+   *
+   * @throws \CRM_Core_Exception
+   * @throws \CiviCRM_API3_Exception
+   */
+  public function testLoadSavedMapping($fieldSpec, $expectedJS) {
+    $form = $this->getFormObject('CRM_Contact_Import_Form_MapField');
+    /* @var CRM_Contact_Import_Form_MapField $form */
+    $form->set('contactType', CRM_Import_Parser::CONTACT_INDIVIDUAL);
+
+    $mapping = $this->callAPISuccess('Mapping', 'create', ['name' => 'my test']);
+    $this->callAPISuccess('MappingField', 'create', array_merge(['mapping_id' => $mapping], $fieldSpec));
+    $result = $this->loadSavedMapping($form, $mapping['id'], 1);
+    $this->assertEquals($expectedJS, $result['js']);
+  }
+
+  /**
+   * Get data for map field tests.
+   */
+  public function mapFieldDataProvider() {
+    return [
+      [
+        ['name' => 'First Name', 'contact_type' => 'Individual', 'column_number' => 1],
+        'document.forms.MapField[\'mapper[1][1]\'].style.display = \'none\';
+document.forms.MapField[\'mapper[1][2]\'].style.display = \'none\';
+document.forms.MapField[\'mapper[1][3]\'].style.display = \'none\';
+',
+      ],
+    ];
+  }
+
+  /**
+   * Wrapper for loadSavedMapping.
+   *
+   * This signature of the function we are calling is funky as a new extraction & will be refined.
+   *
+   * @param \CRM_Contact_Import_Form_MapField $form
+   *
+   * @param int $mappingID
+   * @param int $columnNumber
+   *
+   * @return array
+   *
+   * @throws \CiviCRM_API3_Exception
+   */
+  protected function loadSavedMapping($form, $mappingID, $columnNumber) {
+    list($mappingName, $mappingContactType, $mappingLocation, $mappingPhoneType, $mappingImProvider, $mappingRelation, $mappingOperator, $mappingValue, $mappingWebsiteType) = CRM_Core_BAO_Mapping::getMappingFields($mappingID, TRUE);
+
+    //get loaded Mapping Fields
+    $mappingName = CRM_Utils_Array::value(1, $mappingName);
+    $mappingLocation = CRM_Utils_Array::value(1, $mappingLocation);
+    $mappingPhoneType = CRM_Utils_Array::value(1, $mappingPhoneType);
+    $mappingImProvider = CRM_Utils_Array::value(1, $mappingImProvider);
+    $mappingRelation = CRM_Utils_Array::value(1, $mappingRelation);
+    $mappingWebsiteType = CRM_Utils_Array::value(1, $mappingWebsiteType);
+    $defaults = [];
+    $formName = 'document.forms.MapField';
+    $js = '';
+    $hasColumnNames = TRUE;
+    // @todo - can use metadata trait once https://github.com/civicrm/civicrm-core/pull/15018 is merged.
+    $dataPatterns = [];
+    $columnPatterns = [];
+
+    $return = $form->loadSavedMapping($mappingName, $columnNumber, $mappingRelation, $mappingWebsiteType, $mappingLocation, $mappingPhoneType, $mappingImProvider, $defaults, $formName, $js, $hasColumnNames, $dataPatterns, $columnPatterns);
+    return ['defaults' => $return[0], 'js' => $return[1]];
+  }
+
 }