Ckeditor4: Justify plugin: Alignment buttons disappear from toolbar after disallowContent p{text-align} setup

[jurajkapsz]

Type of report

Bug

Provide detailed reproduction steps (if any)

1. Initially, wanted to allow text alignment via justify plugin only for th td elements.
2. By setting config.disallowedContent = 'p{text-align}';, alignment buttons disappear from toolbar. No problems with other elements e.g. config.disallowedContent = 'h2{text-align}';. CKE configuration:

config.allowedContent = {
      $1: {
        elements: CKEDITOR.dtd,
        attributes: true,
        styles: true,
        classes: true
      }
};
config.disallowedContent = 'p{text-align}';

Expected result

Not being able to set text alignment for configured elements via disallowedContent.

Actual result

Alignment buttons disappeared from toolbar altogether after specifying p{text-align} disallowedContent rule.

Other details

• Browser: Chromium 78
• OS: Ubuntu 18.04
• CKEditor version: 4.13
• Installed CKEditor plugins:
  'about' : 1,
  'basicstyles' : 1,
  'bidi' : 1,
  'blockquote' : 1,
  'clipboard' : 1,
  'contextmenu' : 1,
  'copyformatting' : 1,
  'devtools' : 1,
  'div' : 1,
  'elementspath' : 1,
  'enterkey' : 1,
  'entities' : 1,
  'floatingspace' : 1,
  'format' : 1,
  'horizontalrule' : 1,
  'htmlwriter' : 1,
  'iframe' : 1,
  'image' : 1,
  'indentblock' : 1,
  'indentlist' : 1,
  'justify' : 1,
  'link' : 1,
  'list' : 1,
  'liststyle' : 1,
  'magicline' : 1,
  'maximize' : 1,
  'nbsp' : 1,
  'pagebreak' : 1,
  'pastefromword' : 1,
  'pastetext' : 1,
  'pastetools' : 1,
  'preview' : 1,
  'print' : 1,
  'removeformat' : 1,
  'resize' : 1,
  'save' : 1,
  'selectall' : 1,
  'showblocks' : 1,
  'showborders' : 1,
  'sourcearea' : 1,
  'specialchar' : 1,
  'stylescombo' : 1,
  'tab' : 1,
  'table' : 1,
  'tabletools' : 1,
  'templates' : 1,
  'toolbar' : 1,
  'undo' : 1,
  'wysiwygarea' : 1

[jacekbogdanski]

The issue exists due to the fact that justify uses enter mode tag and text-align attribute to verify if it can be enabled. Responsible code for the issue is here:
https://github.com/ckeditor/ckeditor4/blob/422c2342ee3e6ddc219ec24698aa9dd62a484a78/plugins/justify/plugin.js#L63

[frankfuu]

Any workarounds for this?

[jurajkapsz]

Any workarounds for this?

@frankfuu No.

Edit: Or, sorry, not that I know of.