Fix type hint of @message declaration as the "setWidgetParameters" method allows arrays too

[avstudnitz]

Description

The magic setWidgetParameters method of the \Magento\Widget\Model\Widget\Instance class accepts not only strings as its parameter, but also arrays. If it's an array, it gets transformed to a string automatically before saving. This PR adds the corresponding type hint.

Fixed Issues (if relevant)

The IDE shows a warning if you use an array as a parameter:

This is especially annoying as the getWidgetParameters returns an array. It should be possible to use the same data type for getter and setter of one field.

Manual testing scenarios

Insert the following code into your IDE:

 /** @var WidgetInstance $widget */
$widgetParameters = $widget->getWidgetParameters();
$widget->setWidgetParameters($widgetParameters);

It shouldn't show a warning as displayed in the screenshot above.

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)

[magento-engcom-team]

Hi @avstudnitz. Thank you for your contribution
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[rogyar]

Hi @avstudnitz. Thank you for your collaboration.
That's a good point. I believe there should be 'array' only. Can't figure out a case when we can pass widget parameters as a string

[avstudnitz]

Well, it supports strings, so I think this should be reflected in the docs as well. We might break backwards compatibility otherwise :-)

[magento-engcom-team]

Hi @avstudnitz. Thank you for your contribution.
We will aim to release these changes as part of 2.2.8.
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.