fix(rule-tester): fix parser fallback logic

[rriski]

The docs at https://typescript-eslint.io/packages/rule-tester/#type-aware-testing show that for type-aware rule testing parserOptions needs to be specified. However, like shown in the docs, when parser is omitted then an error: "The first argument to require.resolve must be a string. Received null or undefined" is thrown due to a bug in parser fallback behavior.

PR Checklist

• Addresses an existing open issue: fixes #000
• That issue was marked as accepting prs
• Steps in Contributing were taken

Overview

[typescript-eslint]

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✅ Successfully ran 19 targets

• nx test eslint-plugin --coverage=false
• nx test utils --coverage=false
• nx run types:build
• nx test type-utils --coverage=false
• nx test rule-schema-to-typescript-types --coverage=false
• nx run repo-tools:postinstall-script
• nx test visitor-keys --coverage=false
• nx test typescript-estree --coverage=false
• nx test scope-manager --coverage=false
• nx test repo-tools --coverage=false
• nx test eslint-plugin-internal --coverage=false
• nx test eslint-plugin-tslint --coverage=false
• nx test parser --coverage=false
• nx test ast-spec --coverage=false
• nx run-many --target=typecheck --parallel
• nx run-many --target=lint --parallel
• nx run eslint-plugin:generate:configs
• nx run integration-tests:test
• nx run-many --target=build --parallel --exclude=website --exclude=website-eslint

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[rriski]

Another option is to fix the docs to include parser, let me know which one is preferred.

[bradzacher]

radical! thanks for fixing this!