#basePath

• Type: string

basePath sets the directory from which one flat-config entry is matched. It is a literal directory path, not a glob. Its per-file configuration is inactive outside that directory; explicit TypeScript projects retain the owner-wide behavior described below.

{
  basePath: 'packages/app',
  files: ['src/**/*.ts'],
  ignores: ['src/generated/**'],
  languageOptions: {
    parserOptions: { project: ['./tsconfig.json'] },
  },
  rules: {
    'no-debugger': 'error',
  },
}

In this example, files, ignores, and the explicit project path all start from packages/app. basePath changes only their starting directory; files and ignores keep the same glob syntax and matching behavior as entries without basePath.

An entry containing only basePath, ignores, and an optional name is still a global ignore entry. Its patterns are scoped to the effective base directory and participate in normal lint-target and config-candidate traversal.

#Resolution base

A relative basePath resolves from the ConfigArray base. That base depends on how the config was selected:

An inline override therefore uses the discovered module directory for basePath in automatic mode, and API cwd with an explicit config or overrideConfigFile: true. This matches how ESLint appends overrideConfig to the selected ConfigArray. Relative fields in an inline entry without basePath keep Rslint's existing API-cwd behavior.

For example, if /project invokes an external config:

cd /project
rslint --config /configs/rslint.config.ts

Then basePath: 'app' means /project/app, not /configs/app.

Absolute paths are used as written. An empty string is also valid and still counts as an authored basePath; this matters when an inline override's ordinary path origin differs from its ConfigArray base. Glob characters are literal in basePath, so basePath: 'packages/*' names a directory containing * rather than selecting every package.

#TypeScript projects

basePath moves explicit languageOptions.parserOptions.project literals and globs. It does not move the governing config's implicit tsconfig.json fallback or change Rslint's owner-wide project collection. An explicit project: [] still disables the fallback.

Because explicit projects are collected for the governing config, a missing project can still report an error even when the entry's files patterns select no lint target. See languageOptions.parserOptions.project for the complete project behavior.

#Directory and ignore boundaries

For directory-ignore decisions, a scoped global ignore does not match the effective base directory itself. When basePath points above the selected ConfigArray base, a scoped global ignore cannot prune that base itself. Descendants still match normally relative to basePath.

basePath does not move:

• The config owner or requested scan root
• The root used to collect .gitignore files
• The existing files or ignores matcher and glob grammar

See .gitignore integration for its independent collection rules.

The directory named by basePath does not need to exist when the config loads. Non-string values are rejected immediately; a missing explicit TypeScript project is validated separately.