[Regression] `${configDir}` in extended `tsconfig.json` causes false type-safety errors

[alejandrohdezma]

When a tsconfig.json extends a base config that uses ${configDir} (the TypeScript 5.5 path variable) in outDir, include, or exclude, XO reports spurious errors like:

• Unsafe assignment of an error typed value
• Unsafe call of a type that could not be resolved

Replacing ${configDir} with ../ in the base tsconfig.json makes the errors go away, which indicates XO fails to resolve ${configDir} properly.

Reproduction

https://github.com/alejandrohdezma/xo-repro

The repo has the following setup:

tsconfig.json — extends a base config:

{
  "extends": "./remote_lib/tsconfig.json"
}

remote_lib/tsconfig.json — base config using ${configDir}:

{
  "compilerOptions": {
    "outDir": "${configDir}/dist",
    "resolveJsonModule": true,
    "skipLibCheck": true,
    "strict": true
  },
  "include": ["${configDir}/src/**/*.ts"],
  "exclude": ["${configDir}/node_modules", "${configDir}/dist", "${configDir}/tests"]
}

src/config.ts — simple file using zod:

import {z} from 'zod'

export const Config = z.object({
  something: z.array(z.string()),
  other: z.object({
    something: z.string(),
  }),
})

export type Config = z.infer<typeof Config>

Steps:

1. npm install
2. npm run build (passes correctly)
3. npm run check (produces false errors)
4. Replace ${configDir} with ../ in remote_lib/tsconfig.json
5. npm run check (no errors)

Context

I believe this is a regression — XO 0.60.0 apparently handled this correctly. ${configDir} is important for shared/company-wide base tsconfig.json files distributed as packages, where relative paths like ../ don't work reliably since the consuming project's directory depth is unknown. Without ${configDir}, every consuming project would need to override outDir, include, and exclude.

Workaround

Currently I'm solving this by pinning XO version to 0.60.0.

[alejandrohdezma]

Tested in on the repro repo with:

"overrides": {                                                                                                               
    "get-tsconfig": "4.13.1"                                                                                                   
} 

And working fine now. So all we need to do is update get-tsconfig.