Fix issue with double escaped autolink special characters

[jacekbogdanski]

What is the purpose of this pull request?

Bug fix

Does your PR contain necessary tests?

All patches that change the editor code must include tests. You can always read more
on PR testing,
how to set the testing environment and
how to create tests
in the official CKEditor documentation.

This PR contains

• Unit tests
• Manual tests

Did you follow the CKEditor 4 code style guide?

Your code should follow the guidelines from the CKEditor 4 code style guide which helps keep the entire codebase consistent.

• PR is consistent with the code style guide

What is the proposed changelog entry for this pull request?

* [#4858](https://github.com/ckeditor/ckeditor4/issues/4858): Fixed: [Autolink](https://ckeditor.com/cke4/addon/autolink) plugin incorrectly escapes `&` characters when pasting links into the editor.

What changes did you make?

Links were double escaped by executing 2x setAttribute method with already escaped & character to &.

Which issues does your PR resolve?

Closes #4858

[Comandeer]

Looks good, however there is one edge case that fails after the changes:

https://www.google.com/test/?one=one&=1

If link contains intentional & sequence, it's converted to & instead of &. The same happens with < and other entities mentioned in allEscRegex in tools.js file.

[jacekbogdanski]

The problem with the issue you mentioned is that there is no way (at the moment) to differentiate both escaped and unescaped characters when manipulating HTML in autolink plugin. Feeding autolink plugin with:

• https://www.google.com/test/?one=1&two=2
• https://www.google.com/test/?one=1&two=2
  will always result in passing escaped HTML to

  ckeditor4/plugins/autolink/plugin.js

  Lines 76 to 104 in 9fcdc32

  	function getHtmlToInsert( text ) {
  	// URL will be encoded later on with link.setAttribute method. Avoid
  	// double encoding of special characters (#4858).
  	text = CKEDITOR.tools.htmlDecodeAttr( text );
  	var link = new CKEDITOR.dom.element( 'a' ),
  	value = text.replace( /"/g, '%22' );
  	value = value.match( CKEDITOR.config.autolink_urlRegex ) ? value : 'mailto:' + value;
  	link.setText( text );
  	link.setAttribute( 'href', value );
  	// (#1824)
  	var linkData = CKEDITOR.plugins.link.parseLinkAttributes( editor, link ),
  	attributes = CKEDITOR.plugins.link.getLinkAttributes( editor, linkData );
  	if ( !CKEDITOR.tools.isEmpty( attributes.set ) ) {
  	link.setAttributes( attributes.set );
  	}
  	if ( attributes.removed.length ) {
  	link.removeAttributes( attributes.removed );
  	}
  	link.removeAttribute( 'data-cke-saved-href' );
  	return link.getOuterHtml();
  	}

Both clipboard and typing operate on already processed HTML by a browser using copybin or text matcher.

This issue also exists in the older 4.15.1 version before #4858 regression, so I propose to extract it as a separate ticket as it looks like something more complicated to fix but also very unlikely to happen.

[Comandeer]

LGTM! I've got just some doubts about unit test (see my inline comment).

[Comandeer]

LGTM!