Convert the field handler from a deprecated mediafield to the new file entity module

should this be part of the media module instead?

Yeah I would welcome this to be fully supported in mediafield_uninstall().

Now that mediafield is deprecated, can we expect to have an "upgrade" path to filefield on 7.x-1.0?
This would be great !

It's not too high on the list of priorities since we'll still be support the mediafield, but yes some time down the road we'll need a migration to move those fields to file fields. The code above is a start but it needs work to make it a more generic migration.

Thanks avillanueva-npr !
That really came in handy! I adapted it a bit to handle the 2 issues you just spoke about.

/**
 * Controller for helloworld_convert_mediafield
 * I suppose it would be better to iterate through all records in table field_config
 * and convert everything with a 'media' type, but that would've been overkill.
 * Besides, you still need to edit the associated content types afterwards. -aDarkling-
 */
function helloworld_convert_mediafields_util() {
	helloworld_convert_mediafield('field_lead_image');
	helloworld_convert_mediafield('field_am_section_image');
	return t('Done converting deprecated media fields to file fields.');
}

/** Generic D7 Media 2.x mediafield -> filefield conversion script.
 * Adapted from avillanueva-npr's code at http://drupal.org/node/1493454
 * @param string $field
 */
function helloworld_convert_mediafield($field) {
$field_display = $field.'_display';
$display_sepc = array (
  'description' => 'Flag to control whether this file should be displayed when viewing content.',
  'type' => 'int',
  'size' => 'tiny',
  'default' => 1,
  'unsigned' => TRUE,
  'not null' => TRUE,
);

$field_description = $field.'_description';
$description_sepc = array (
  'description' => 'A description of the file.',
  'type' => 'text',
  'not null' => FALSE,
);

// Change the associated table structures
db_add_field("field_data_$field", $field_display, $display_sepc);
db_add_field("field_data_$field", $field_description, $description_sepc);
db_add_field("field_revision_$field", $field_display, $display_sepc);
db_add_field("field_revision_$field", $field_description, $description_sepc); 

// Can we delete the old columns in these tables?
// My installation had no problem with it, but check your tables for any 
// non-null values just in case.
db_drop_field("field_data_$field", $field.'_title');
db_drop_field("field_data_$field", $field.'_data');
db_drop_field("field_revision_$field", $field.'_title');
db_drop_field("field_revision_$field", $field.'_data');

// Add the data to config
$result = db_update('field_config')
  ->fields(array(
    'type' => 'file',
    'module' => 'file',
  ))
  ->condition('field_name', $field)
  ->execute();
	;
}

Realizing we have two issues open for the same thing, so I need to mark this as a duplicate of #1349058: Convert 'Media' fields to 'File' fields that use the 'Media file selector' widget. I'm going to cross-reference it to ensure we don't lose the code that's been provided here if it can be useful.

Minor formatting changes