Drupal validation solution when using file upload with other required form field

Question

I am having problem while trying to upload a picture in a form that also has other required field. So if I dont enter anything on the required field and upload the picture, I lose the picture that's uploaded (during the form validation the picture is no longer there). I can't print it anywhere in form_state and all. How can I have a file upload inside a form with other form elements which are required? I dont want user to upload the picture again if the user forgets to enter the info in the other required field.

Any ideas?

    function form() {
    $form['#attributes'] = array('enctype' => "multipart/form-data");
    //'upload' will be used in file_check_upload()
    $form['upload'] = array('#type' => 'file');
    $form['my_require_field'] = array(
        '#type' => 'textfield',
        '#title' => t('Enter code here'),
        '#default_value' => 1,
        '#size' => 20,
        '#required' => TRUE
      );
    }
    function form_validate() {
     if(!file_check_upload('upload')) {
     form_set_error('upload', 'File missing for upload.');
    }
    }
    function form_submit() {
     $file = file_check_upload('upload');
    }

Answer 1

You should use the managed_file type id you are using Drupal 7

 $form['upload'] = array(
      '#type' => 'managed_file',
      '#title' => t('Upload Image'),
      '#default_value' => '',
      '#required' => TRUE,
      '#description' => t("Upload Image description"),
    );

In your submit handler you can write following:

// Load the file via file fid.
$file = file_load($form_state['values']['upload']);

// Change status to permanent and save.
$file->status = FILE_STATUS_PERMANENT;
file_save($file);

Hope this will help!

Answer 2

For Drupal 8

It appears that such basic functionality as making field of type file (not managed_file) required is not supported out of the box.

One need to implement custom validator for this field in formValidate() method. A rare example of such functionality can be found in ConfigImportForm.php file.

Here is a snippet of code to handle file field setup in the form, required validation and submission.

<?php

class YourForm extends FormBase {

  public function buildForm(array $form, FormStateInterface $form_state) {
    $form['myfile'] = [
      '#title' => $this->t('Upload myfile'),
      '#type' => 'file',
      // DO NOT PROVILDE '#required' => TRUE or your form will always fail validation!
    ];
  }

  public function validateForm(array &$form, FormStateInterface $form_state) {
    $all_files = $this->getRequest()->files->get('files', []);
    if (!empty($all_files['myfile'])) {
      $file_upload = $all_files['myfile'];
      if ($file_upload->isValid()) {
        $form_state->setValue('myfile', $file_upload->getRealPath());
        return;
      }
    }

    $form_state->setErrorByName('myfile', $this->t('The file could not be uploaded.'));
  }

  public function submitForm(array &$form, FormStateInterface $form_state) {
    // Add validator for your file type etc.
    $validators = ['file_validate_extensions' => ['csv']];
    $file = file_save_upload('myfile', $validators, FALSE, 0);
    if (!$file) {
      return;
    }

    // The rest of submission processing.
    // ...
  }
}

From https://api.drupal.org/comment/63172#comment-63172