Adding hook to alter imported files

Can you explain why the hook hook_file_presave() is not sufficient for your use case?

Can you also explain what your patches are doing? Your latest patch seems to change a lot of code and I'm curious why so many changes are needed for just invoking a new hook.

1. +++ b/mappers/file.inc
   @@ -184,7 +191,11 @@ function file_feeds_set_target(FeedsSource $source, $entity, $target, array $val
   +            // Flag the current result path, set the value and unflag the path.
   +            _feeds_insert_unique_array_last($result_item_path, $k);
   ...
   +            _feeds_delete_unique_array_last($result_item_path, $k);
   

   It sounds like some nested value in an array is parsed here. Can you give some example data that clarifies why something in a multidimensional array needs to be searched?

2. +++ b/plugins/FeedsParser.inc
   @@ -458,11 +458,34 @@ class FeedsEnclosure extends FeedsElement {
   +  public function getFile($destination, $replace = FILE_EXISTS_RENAME, $source = null, $mapping = null, array $result_item_path = array(), FeedsParserResult $result = null) {
   

   What is $result_item_path and why is the FeedsParserResult needed here?

3. +++ b/plugins/FeedsParser.inc
   @@ -458,11 +458,34 @@ class FeedsEnclosure extends FeedsElement {
   +      //Extract subfields into an array.
   +      $subfields = array();
   +      if(isset($result)){
   +        $result_current_item = $result->currentItem();
   +        if(!empty($result_current_item)){
   +          $field_name = array_shift(explode(':', $mapping['target']));
   +          foreach($source->importer->processor->config['mappings'] as $_mapping){
   +            $targets = explode(':', $_mapping['target']);
   +            if(in_array($field_name, $targets)){
   +              $subfield_name = $targets[1];
   +              $value = $result_current_item[$_mapping['source']];
   +              if(!empty($value)){
   +                $subfields[$subfield_name] = _feeds_get_array_child_by_keys($value, $result_item_path);
   +              }
   +            }
   +          }
   +          // Unset because we are in this case (getFile() called only in 'uri').
   +          unset($subfields['uri']);
   +        }
   +      }
   

   What happens here and why is access to the parser result important here?

4. +++ b/plugins/FeedsProcessor.inc
   @@ -814,14 +814,8 @@ abstract class FeedsProcessor extends FeedsPlugin {
   -    // This is where the actual mapping happens: For every mapping we invoke
   -    // the parser's getSourceElement() method to retrieve the value of the
   -    // source element and pass it to the processor's setTargetElement() to stick
   -    // it on the right place of the target item.
   ...
   -      $value = $this->getSourceValue($source, $result, $mapping['source']);
   
   @@ -855,31 +849,38 @@ abstract class FeedsProcessor extends FeedsPlugin {
   +    // This is where the actual mapping happens: For every mapping we invoke
   +    // the parser's getSourceElement() method to retrieve the value of the
   +    // source element and pass it to the processor's setTargetElement() to stick
   +    // it on the right place of the target item.
   +    $value = $this->getSourceValue($source, $result, $mapping['source']);
   

   Why is it that this code needed to be moved?

5. +++ b/plugins/FeedsProcessor.inc
   @@ -855,31 +849,38 @@ abstract class FeedsProcessor extends FeedsPlugin {
   +   * @param mixed $field_name
   +   *   The field_name.
   

   $target !== $field_name. A feeds target is in most cases a field, but not always. It can also be a property on an entity.

6. +++ b/plugins/FeedsProcessor.inc
   @@ -855,31 +849,38 @@ abstract class FeedsProcessor extends FeedsPlugin {
   +  protected function mapToTarget(FeedsSource $source, $field_name, &$target_item, array $mapping, FeedsParserResult $result) {
   

   Changing the method signature here possibly breaks modules that are overriding this method.