Incorrect generated file paths when using Yarn 2 for virtual packages

[snasirca]

Yarn 2 will create virtual packages for those dependencies that have peer dependencies. The Karma plugins that we use such as karma-requirejs have a peer dependency on karma. The virtual package path that Yarn 2 generates is:

/Users/shahn/my-project-dir/.yarn/$$virtual/karma-requirejs-virtual-d16b0e1d06/0/cache/karma-requirejs-npm-0.2.5-fb217d2fa2-3.zip/node_modules/karma-requirejs/

So for example the karma-requirejs plugin will try to load the lib/adapter.js file which would resolve to this path:

/Users/shahn/my-project-dir/.yarn/$$virtual/karma-requirejs-virtual-d16b0e1d06/0/cache/karma-requirejs-npm-0.2.5-fb217d2fa2-3.zip/node_modules/karma-requirejs/lib/adapter.js

Problem is that the Karma middleware will try to generate the HTML file with all these paths but it uses the replace() function in JS and the double dollar sign $$ is a special pattern. It means replace with $. So the paths generated to put in the HTML code is:

/Users/shahn/my-project-dir/.yarn/$virtual/karma-requirejs-virtual-d16b0e1d06/0/cache/karma-requirejs-npm-0.2.5-fb217d2fa2-3.zip/node_modules/karma-requirejs/lib/adapter.js

This errors out with 404s.

There are several ways to go about fixing this but I figured I just pass in an arrow function instead and that would turn off the special patterns.

[devoto13]

Fixed by #3663