test files create parser issue

[EdJoPaTo]

As one example of many (one per file within test/):

test/math/probability.ts
✖    0:0    Parsing error: If "parserOptions.project" has been set for @typescript-eslint/parser, …/test/math/probability.ts must be included in at least one of the projects provided.

[sindresorhus]

parserOptions.project has to be set for some of the rules to work. If we didn't set it here, you would have to set it yourself, and the result would be the same.

See typescript-eslint/typescript-eslint#890

[EdJoPaTo]

As xo also includes rules for Ava I would assume it works out of the box with ava tests. Which is the purpose of xo: work with as little config as possible.

[fregante]

The solution suggested in typescript-eslint/typescript-eslint#890 seems to work:

// tsconfig.xo.json
{
	"extends": "@sindresorhus/tsconfig",
	"files": [
		"index.ts",
		"index.test-d.ts"
	]
}

// package.json
{
  "xo": {
    "extensions": [
      "ts"
    ],
    "extends": "xo-typescript",
    "parserOptions": {
       "project": "./tsconfig.xo.json"
    }
  }
}

Edit: none of this config is needed anymore in XO 0.28.3! 🤩

[sindresorhus]

@fregante This is not an XO issue. The problem is in TypeScript-ESLint. I'm happy to consider ways for XO to simplify this though.

[fregante]

Yeah this is an annoying requirements of ts-eslint.

I'm happy to consider ways XO to simplify this though.

XO could:

• avoid linting TS files not included in tsconfig (not great)
• detect the error and suggest the above solution, if possible
• since xo is setting the project prop, perhaps it can also generate/extend one on the fly, but it's probably hard to accomplish.

I don't know of a better solution to the problem in the first place