Bug: Notebook Editor, Interactive Window, Editor cells

Steps to cause the bug to occur

1. Upgrade VScode from version 2019.10.44104 to 2019.11.49689
2. Attempt to open a .ipynb file such containing certain MathJAX code in VSCode. For instance, at least one example from the Jupyter MathJax Documentation no longer works (see below). This is the code used in the GIF above.

$$ \begin{equation*} \mathbf{V}_1 \times \mathbf{V}_2 = \begin{vmatrix} \mathbf{i} & \mathbf{j} & \mathbf{k} \\\ \frac{\partial X}{\partial u} & \frac{\partial Y}{\partial u} & 0 \\\ \frac{\partial X}{\partial v} & \frac{\partial Y}{\partial v} & 0 \end{vmatrix} \end{equation*} $$

Copy-pasting the above code into this MathJax Demo shows the correct output.

Actual behavior

1. The MathJax code doesn't compile. Interestingly, if I open the notebook in a browser (say Chrome), the MathJax code renders fine. Reverting to version 2019.10.44104 also works.
2. Get "Couldn't start client python tools" and "Encountered an Issue downloading the language server" warning messages. I'm not sure if both of these are related. Edit: I fixed these errors by following this. The MathJax errors remain.

Expected behavior

1. Valid MathJax code compiles and renders output.
2. No errors.

Your Jupyter and/or Python environment

Please provide as much info as you readily know

• Jupyter server running: Local
• Extension version: 2019.11.49689
• VS Code version: 1.40.1
• Setting python.jediEnabled: false
• Python and/or Anaconda version: 3.6.8
• OS: Windows
• Virtual environment: N/A

Developer Tools Console Output

Microsoft Data Science for VS Code Engineering Team: @rchiodo, @IanMatthewHuff, @DavidKutu, @DonJayamanne, @greazer