Fix viewer utils in order to send only valid XML to the server

[psala-at-wiris]

Description

Some user inputs were causing the server to fail due to malformed XML. When retrieving MathML, the generated text is transformed into HTML, which is not 100% compatible with XML. The current solution uses the browser's native XMLParser to transform HTML into XML and ensures that only valid XML is sent to the server.

Steps to reproduce

Unit tests

• Run unit tests in this package with: yarn jest .

Ui

• Open the html-viewer
• Paste some problematic formulas to text-box and check an image is generated with no errors:
  • <math xmlns="http://www.w3.org/1998/Math/MathML"><mo mathvariant="bold" mathcolor="#7F0000" mathsize="48px">&#xAB;</mo><mo mathvariant="bold" mathcolor="#7F0000" mathsize="48px">&lt;</mo><mo mathvariant="bold" mathcolor="#7F0000" mathsize="48px">&#xBB;</mo><mo mathvariant="bold" mathcolor="#7F0000" mathsize="48px">&gt;</mo><mo mathvariant="bold" mathcolor="#7F0000" mathsize="48px">&#xA7;</mo><mo mathvariant="bold" mathcolor="#7F0000" mathsize="48px">&amp;</mo><mo mathvariant="bold" mathcolor="#7F0000" mathsize="48px">&#xA8;</mo><mo mathvariant="bold" mathcolor="#7F0000" mathsize="48px">&quot;</mo><mo mathvariant="bold" mathcolor="#7F0000" mathsize="48px">'</mo><mo mathvariant="bold" mathcolor="#7F0000" mathsize="48px">'</mo></math>

  • <math><mn mathcolor="red">&quot;4</mn><mo>×</mo><mi>x</mi></math>

#taskid 45734

Changes.md

fix: change htmlEntitiesToXmlEntities' implementation in order to assure only valid XML

[usantos-at-wiris]

Great way to solve it! Good job!