Alter date field granularity on exposed filter mid-request

Question

I have an exposed filter on a date value that has it's granularity set to month, so it shows possible year and month values in the form. If I select just a year, no results are returned, even though I know there are posts that should be retrieved based on the year. If I then specify a month, all posts from that month and year are returned.

I need to be able to return results from the entire year when just year is selected. I'm thinking there might be a way to alter the granularity somehow during the request based on whether or not the month was specified? Any thoughts?

Answer 1

Working solution thus far:

/**
 * Impliments hook_form_views_exposed_form_alter
 *
 * Used to change exposed date filter to year only, as this is not available in the views UI
 */
function bain_views_form_views_exposed_form_alter(&$form, $form_state)
{
    if( $form['#id'] == 'views-exposed-form-news-items-page')
    {
        // dpm($form_state['input']['date']['value']);
        if (isset($form_state['input']['date']['value'])
            && empty($form_state['input']['date']['value']['month']))
        {
            // Switch date formatter to year only
            $form['date']['value']['#date_format'] = 'Y';
            // Add extra validator to handle filter submit
            $form['#validate'][] = 'bain_views_views_exposed_form_validate';
        }
    }
}

/**
 * Custom validator for exposed date filter
 */
function bain_views_views_exposed_form_validate(&$form, &$form_state)
{
    if ($form['#id'] == 'views-exposed-form-news-items-page')
    {
        $handlers = &$form_state['view']->filter;
        $date_handler = $handlers['field_news_date_value'];
        // dpm($date_handler);
        if (!empty($date_handler->options['exposed'])
            && isset($form['date']['value']['#type'])
            && $form['date']['value']['#type'] == 'date_select'
            && $form['date']['value']['#date_format'] == 'Y')
        {
            $date_handler->options['granularity'] = 'year';
            $date_handler->format = 'Y';
        }
    }
}