Required-Attribute not correctly translated between Source- and WYSIWYG-Editor

[sbusse]

Steps to reproduce

1. Goto ​http://ckeditor.com/demo#full
2. Open Source-View and delete it's content
3. Add the following line:
4. <input checked required type="checkbox" />
5. Switch to WYSIWYG-View and then back to Source-View

Expected result

<input checked="checked" required="required" type="checkbox" />

Actual result

<input checked="checked" required="" type="checkbox" />

This happens with any input element with required attribute set and leads to the problem that if you edit the input element in the WYSIWYG-Editor, the required checkbox will be unchecked.

In our setup, we create the input element with WYSIWYG as required="required", it get's saved on the database as required (without value) and then loaded from datebase somewhen later resulting in a required="".

Other details (browser, OS, CKEditor version, installed plugins)

Browser: 47.0.2526.106 OS: Ubuntu 14.04 CKEditor: 4.5 Plugin: Forms

[Jakub Ś]

First of all, this issue has been fixed recently in: #11583

Second, the value required, required="" and required="required" mean the same thing - field is required. Please see:
​https://html.spec.whatwg.org/multipage/forms.html#concept-input-required
​https://html.spec.whatwg.org/multipage/infrastructure.html#boolean-attribute
​http://www.w3.org/TR/2012/WD-html5-20121025/common-input-element-attributes.html#the-required-attribute
​http://www.w3.org/TR/2012/WD-html5-20121025/common-microsyntaxes.html#boolean-attribute

The problem is that the dialog treats required="" (also required because it is changed to required="") as empty value. We should either make boolean attributes treated as non-empty when they are present tag or assign them attribute name as value e.g. checked=checked.

I haven't found any list of boolean attributes for reference though. There are definitely required, checked, disabled, multiple and ...?

[Jakub Ś]

NOTE: as a workaround you need to use required="required" all the time.

[rzueger]

I fixed this issue and submitted a pull request:

​https://github.com/ckeditor/ckeditor-dev/pull/276

With my fix, the required checkbox is checked - according to the HTML spec - if the value is an empty string or "required" (if the attribute is set without a value in the source code, CKEditor automatically sets an empty string as value).

Please have a look at the pull request. We are not able to use required="required" all the time - therefore, we need the fix as soon as possible.

[Tade0]

Included the changes from the PR, rebased with major, added manual test.

Changes pushed to ​branch:t/14291.