Exposed filters fire "An illegal choice has been detected. Please contact the site administrator." error

This patch solved my problems.
Thanks!

How can I appeal for this patch to be included into Views module, so it will also be available after the Views update?

My error did not disappear with the patch.

Thank you Hugh - my life and sanity have now been saved by your patch. I was starting to think Views was *gasp* not as amazing as everyone believes.

Still - it is daft this hasn't been committed as of yet?

Just running the tests.

Some trailing whitespaces in the patch. Set your IDE to trim these on save :)

After patching I still had this issue.

@hughworm
That looks like an issue with the testing system. Re-queued.

[edit]
Sorry, no idea why this is doing this!

BTW, a code search finds about 40 all and 40 All in the code base ('all' and 'All'). I found trying to fix singular errors started to peculate additional bugs into other areas. I ended up hacking it by setting the correct $_GET parameter using hook_init() for the view that was having issues.

I tried the patch in #3. It didn't fix it for me.

I got it working by using Alan D's hook_init() code which sets it to 'All' if it hasn't been set.

...

Don't know if this will help anyone...
but I was using group filters and had an extra BLANK field under my defined filters. Once I deleted the empty field the error went away.

I had the same issue and created the following workaround. (Assume favorite as your filter name inside $parameters)

  // Avoid An illegal choice error.
    $parameters = drupal_get_query_parameters();
    $options = array(
      'favorited' => t('Favorited'),
      'unfavorited' => t('Unfavorited'),
    );
    // Ensure that $value is a valid option.
    if (isset($parameters['favorite']) && array_key_exists($parameters['favorite'], $options)) {
      $value = $parameters['favorite'];
    }
    else {
      $value = '';
    }

    $form['value'] = array(
      '#type' => 'select',
      '#title' => t('Favorite'),
      '#value' => $value,
      '#options' => $options,
    );

This is nearly necessary for #2578785: Large-scale location mapping in Drupal 8 (Views) if you want exposed filters on Leaflet GeoJSON views; adding as related. I don't yet know if this is even an issue in D8.

I think this issue is pretty redundant now, further discussions over in: #1177882: Exposed filters fire "An illegal choice has been detected. Please contact the site administrator." error.