#basePath

• Type: string

basePath sets the directory from which one flat-config entry is matched. It is a literal directory path, not a glob. The entry's lint settings apply only to matching files within that directory.

{
  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 ignore patterns start from the basePath directory.

#Resolution base

A relative basePath resolves from a directory determined by how the config was selected:

An inline override therefore uses the discovered config directory for basePath in automatic mode, and API cwd with an explicit config or overrideConfigFile: true. Without basePath, relative paths in an inline override resolve from API cwd.

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 uses the directory in the table's basePath column. Glob characters are literal in basePath, so basePath: 'packages/*' names a directory containing * rather than selecting every package.

#TypeScript projects

Relative languageOptions.parserOptions.project paths and glob patterns resolve from basePath. An explicit tsconfigRootDir overrides that base; resetting it to null in JavaScript configuration restores the entry's basePath.

For linting, a later matching project value replaces an earlier list and uses the basePath of the entry that supplies it. project: [], false, or null clears explicit projects for matching files. Automatic discovery can still run when projectService: true is combined with project: false or null; combining it with project: [] is an error. See parser options.

basePath does not change where projectService stops searching parent directories; use tsconfigRootDir for that. It also does not move the default tsconfig.json lookup beside the Rslint config used by the type-check commands. Ordinary lint does not use that default.

--type-check and --type-check-only check all listed projects, including those in entries whose files patterns select no lint files. A missing project path can therefore cause these commands to fail even if no lint files match that entry. See what gets type-checked.

#Directory and ignore boundaries

Global ignore patterns scoped with basePath can ignore files and subdirectories, but not the basePath directory itself. If basePath points above the config's resolution base shown in the table, the patterns cannot ignore that resolution base itself either.

basePath does not move:

• Which Rslint config is used or which directory the command scans
• The root used to collect .gitignore files
• The pattern syntax for files or ignores

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.