The new tsconfig loading feature implemented in #471 doesn't properly support extended tsconfig files. For example take the following config for our test files that extends our base config:

tests/tsconfig.json

{
  "extends": "../tsconfig.json",
  "include": [
    "./**/*.ts"
  ],
}

tsconfig.json

{
  "compilerOptions": {
    /* shared compiler options set here */
  }
  "include": {
    "src/**/*.ts",
    "src/**/*.vue"
  }
}

When the tests are run the config that is loaded and passed to the typescript compiler doesn't include any of the options set in the base config even though tests/tsconfig.json properly extends it. Note this was working previously before this PR was merged.

It looks like this was an issue in the past as well but was fixed and now has appeared again.
#118
#139