MAGETWO-61209: Backport - Fixed issue #7379 with mage/calendar when setting `numberOfM…

[vasilii-b]

Description

The full description of the issue and steps to reproduce are provided in #7379.
The same issue is reproduced on Magento 2.1, Magento 2.2 and Magento 2.3-develop

Fixed Issues

1. Calendar widget (jQuery UI DatePicker) with numberOfMonths = 2 or more #7379: Calendar widget (jQuery UI DatePicker) with numberOfMonths = 2 or more

Manual testing scenarios

The easiest way to see the issue in action is to add a new field in the Magento_Contact form that is gonna use a calendar.

Field to add:

<div class="field availability">
  <label class="label" for="availability"><span><?= $block->escapeHtml(__('Availability')) ?></span></label>
   <div class="control">
       <input name="availability" id="availability" title="<?= $block->escapeHtmlAttr(__('Availability')) ?>"
            value="<?= $block->escapeHtmlAttr($this->helper('Magento\Contact\Helper\Data')->getPostValue('availability')) ?>" class="input-text" type="text" />
  </div>
</div>

Initialize the calendar:

<script>
    require(['jquery', 'mage/calendar'], function($, calendar) {
       $('#availability').calendar({
           numberOfMonths: [1, 2]
       });
    });
</script>

You should see only 2 months displayed, like this:

Contribution checklist

• Pull request has a meaningful description of its purpose
• All commits are accompanied by meaningful commit messages
• All new or changed code is covered with unit/integration tests (if applicable)
• All automated tests passed successfully (all builds on Travis CI are green)

Original PR

#16278

[magento-engcom-team]

Hi @vasilii-b. Thank you for your contribution
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[rogyar]

Hi @vasilii-b. Thank you for the fix, works like a charm.

[vasilii-b]

@rogyar can you please advice what to do next here as the Travis failed with an integration test ?
Is there anything needed from my side ?
Thank you!

[magento-engcom-team]

Hi @vasilii-b. Thank you for your contribution.
The changes from your Pull Request should be available with the upcoming 2.2.6 release.
Please check the release notes for final confirmation.

Please, consider to port this solution to 2.3 release line.
You may use Porting tool to port commits automatically.