This is a sample custom visual for Power BI that uses Code Mirror to display code. This repo is for allow to verify that there is an error in the Power BI Visual Tools that prevents the use of Code Mirror language syntax in custom visuals.
You can just clone this repo and run the pbiviz start command to see the error in the console.
If you disable the import of @codemirror/lang-xml in the src/visual.ts file, the visual will work correctly.