Mathjax: \overbrace and \underbrace cause nodejs conversion errors in both tex input and mml input

[shiblon]

Issue Summary

When using \overbrace or \underbrace in displaymath, the node demos tex2svg and mml2svg do not work. The following error is thrown:

TypeError: Cannot read property 'chars' of undefined                                                                                                                                                       
    at SVGmo.CommonWrapper.unicodeChars (/home/shiblon/chris/jstext/tmp/MathJax-demos-node/node_modules/mathjax-full/js/output/common/Wrapper.js:433:48)                                                   
    at SVGmo.SVGWrapper.placeChar (/home/shiblon/chris/jstext/tmp/MathJax-demos-node/node_modules/mathjax-full/js/output/svg/Wrapper.js:206:45)                                                            
    at SVGmo.addGlyph (/home/shiblon/chris/jstext/tmp/MathJax-demos-node/node_modules/mathjax-full/js/output/svg/Wrappers/mo.js:109:21)                                                                    
    at SVGmo.addMidH (/home/shiblon/chris/jstext/tmp/MathJax-demos-node/node_modules/mathjax-full/js/output/svg/Wrappers/mo.js:194:14)                                                                     
    at SVGmo.stretchHorizontal (/home/shiblon/chris/jstext/tmp/MathJax-demos-node/node_modules/mathjax-full/js/output/svg/Wrappers/mo.js:94:34)                                                            
    at SVGmo.stretchSVG (/home/shiblon/chris/jstext/tmp/MathJax-demos-node/node_modules/mathjax-full/js/output/svg/Wrappers/mo.js:73:18)                                                                   
    at SVGmo.toSVG (/home/shiblon/chris/jstext/tmp/MathJax-demos-node/node_modules/mathjax-full/js/output/svg/Wrappers/mo.js:52:18)                                                                        
    at SVGmover.toSVG (/home/shiblon/chris/jstext/tmp/MathJax-demos-node/node_modules/mathjax-full/js/output/svg/Wrappers/munderover.js:77:16)                                                             
    at SVGmrow.SVGWrapper.addChildren (/home/shiblon/chris/jstext/tmp/MathJax-demos-node/node_modules/mathjax-full/js/output/svg/Wrapper.js:61:23)                                                         
    at SVGmrow.toSVG (/home/shiblon/chris/jstext/tmp/MathJax-demos-node/node_modules/mathjax-full/js/output/svg/Wrappers/mrow.js:27:14)  

Occurring when using any mml2svg or tex2svg node binary.

Steps to Reproduce:

Example input causing failure:

<math display="block" xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mtable><mtr><mtd columnalign="right"><mi>f</mi><mo stretchy="false" form="prefix">(</mo><mi>x</mi><mo stretchy="false" form="postfix">)</mo></mtd><mtd columnalign="left"><mo>=</mo><msup><mi>x</mi><mn>2</mn></msup><mo>+</mo><mn>2</mn><mi>x</mi><mo>+</mo><mn>3</mn></mtd></mtr><mtr><mtd columnalign="right"><mi>f</mi><mo stretchy="false" form="prefix">(</mo><mn>10</mn><mo stretchy="false" form="postfix">)</mo></mtd><mtd columnalign="left"><mo>=</mo><munder><msup><mn>10</mn><mn>2</mn></msup><mo accent="true">⏟</mo></munder><mo>+</mo><mn>2</mn><mo stretchy="false" form="prefix">(</mo><mn>10</mn><mo stretchy="false" form="postfix">)</mo><mo>+</mo><mn>3</mn></mtd></mtr><mtr><mtd columnalign="right"></mtd><mtd columnalign="left"><mo>=</mo><mover><mn>100</mn><mo accent="true">⏞</mo></mover><mo>+</mo><munder><mrow><mn>2</mn><mo stretchy="false" form="prefix">(</mo><mn>10</mn><mo stretchy="false" form="postfix">)</mo></mrow><mo accent="true">⏟</mo></munder><mo>+</mo><mn>3</mn></mtd></mtr><mtr><mtd columnalign="right"></mtd><mtd columnalign="left"><mo>=</mo><munder><mrow><mn>100</mn><mo>+</mo><mover><mn>20</mn><mo accent="true">⏞</mo></mover></mrow><mo accent="true">⏟</mo></munder><mo>+</mo><mn>3</mn></mtd></mtr><mtr><mtd columnalign="right"></mtd><mtd columnalign="left"><mo>=</mo><munder><mrow><mover><mn>120</mn><mo accent="true">⏞</mo></mover><mo>+</mo><mn>3</mn></mrow><mo accent="true">⏟</mo></munder></mtd></mtr><mtr><mtd columnalign="right"></mtd><mtd columnalign="left"><mo>=</mo><mover><mn>123</mn><mo accent="true">⏞</mo></mover></mtd></mtr></mtable></semantics></math>

Attempting to convert that mml expression using mml2svg causes the exception mentioned above.

The same input, but with over/under braces converted to over/under parens follows, and this does not cause the error, but converts properly:

<math display="block" xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mtable><mtr><mtd columnalign="right"><mi>f</mi><mo stretchy="false" form="prefix">(</mo><mi>x</mi><mo stretchy="false" form="postfix">)</mo></mtd><mtd columnalign="left"><mo>=</mo><msup><mi>x</mi><mn>2</mn></msup><mo>+</mo><mn>2</mn><mi>x</mi><mo>+</mo><mn>3</mn></mtd></mtr><mtr><mtd columnalign="right"><mi>f</mi><mo stretchy="false" form="prefix">(</mo><mn>10</mn><mo stretchy="false" form="postfix">)</mo></mtd><mtd columnalign="left"><mo>=</mo><munder><msup><mn>10</mn><mn>2</mn></msup><mo accent="true">⏝</mo></munder><mo>+</mo><mn>2</mn><mo stretchy="false" form="prefix">(</mo><mn>10</mn><mo stretchy="false" form="postfix">)</mo><mo>+</mo><mn>3</mn></mtd></mtr><mtr><mtd columnalign="right"></mtd><mtd columnalign="left"><mo>=</mo><mover><mn>100</mn><mo accent="true">⏜</mo></mover><mo>+</mo><munder><mrow><mn>2</mn><mo stretchy="false" form="prefix">(</mo><mn>10</mn><mo stretchy="false" form="postfix">)</mo></mrow><mo accent="true">⏝</mo></munder><mo>+</mo><mn>3</mn></mtd></mtr><mtr><mtd columnalign="right"></mtd><mtd columnalign="left"><mo>=</mo><munder><mrow><mn>100</mn><mo>+</mo><mover><mn>20</mn><mo accent="true">⏜</mo></mover></mrow><mo accent="true">⏝</mo></munder><mo>+</mo><mn>3</mn></mtd></mtr><mtr><mtd columnalign="right"></mtd><mtd columnalign="left"><mo>=</mo><munder><mrow><mover><mn>120</mn><mo accent="true">⏜</mo></mover><mo>+</mo><mn>3</mn></mrow><mo accent="true">⏝</mo></munder></mtd></mtr><mtr><mtd columnalign="right"></mtd><mtd columnalign="left"><mo>=</mo><mover><mn>123</mn><mo accent="true">⏜</mo></mover></mtd></mtr></mtable></semantics></math>

Technical details:

• MathJax mml2svg reports version 3.0.5
• git log shows commit 967c7f6460ff6cb25c7fe7b7626a0ef02a66f64c at the top
• Client OS: Ubuntu, same on latest Mac OS
• using NodeJS v10.21.0, npm version 6.14.6

[dpvc]

This is the same issue as #2402, and the work-around listed there should resolve the problem. It will be fixed in v3.1, which will be related this week.

[shiblon]

Okay, thanks! Looked different based on error messages, so your additional
insight is very appreciated.

[dpvc]

Fixed in v3.1 released today.