Publint is a specialized linter designed for npm packages, ensuring they maintain the widest compatibility across diverse JavaScript environments. While standard linters often focus on source code style, Publint examines the actual artifacts produced for publication, such as the package.json configuration and bundled files. It validates these against requirements for various runtimes and build tools including Vite, Webpack, Rollup, and Node.js. By catching configuration mistakes and deviations from best practices, it helps package authors prevent common issues that might break compatibility for end-users, such as incorrect export conditions, invalid file formats, or improper usage of deprecated fields.

The tool functions by analyzing the structure and content of a package as it would appear when installed by a user. It can either be run directly on a local directory, which simulates the packing process, or against a pre-existing tarball. When used in a development environment, it inspects entrypoints, export mappings, and dependency declarations to ensure they adhere to modern standard conventions, including those required by TypeScript and Node.js module resolution algorithms. By focusing on the final distributed package, Publint provides actionable feedback that directly impacts the reliability and interoperability of the library in the wild.

Some of the key features are:

• Export Validation: Automatically checks the exports and imports fields in package.json for correct order, syntax, and compatibility.
• Format Consistency: Detects issues with ESM and CommonJS interop, identifying potential dual-package hazards and invalid file extensions.
• TypeScript Compliance: Verifies that type definitions are correctly exposed and associated with their corresponding JavaScript entrypoints.
• Best Practices Enforcement: Flags the use of deprecated fields, suggests sideEffects configuration for improved tree-shaking, and validates repository metadata.
• Environment Awareness: Provides specialized checks for browser-specific conditions and Node.js compatibility.
• Flexible Integration: Supports a command-line interface for CI/CD pipelines, a JavaScript API for programmatic usage, and a web-based interface for quick checks.
• Customizable Severity: Allows users to filter findings by severity level or treat warnings as errors to enforce stricter standards.

Operationally, Publint can be utilized via its web dashboard, where users can search for npm packages or paste links to quickly audit them. For local development, it is installed via npm, yarn, or pnpm and executed as a command-line tool. The CLI supports passing custom options to control the package manager used for packing, filtering output by severity, and setting strict mode. Developers can also integrate the tool into their CI/CD workflows to automatically gate releases if the package fails specified linting criteria, ensuring consistent quality across all versions.

Some common use cases include:

• CI/CD Integration: Automatically running linting checks during the build process before publishing a package to the npm registry.
• Package Auditing: Validating the health of a project configuration to ensure it works correctly across multiple bundlers and runtime versions.
• Dependency Maintenance: Debugging unexpected resolution issues reported by users when using a library in specific environments like Vite or Webpack.
• Type Checking: Ensuring dual-published libraries correctly define their types for both ESM and CommonJS consumers to prevent TypeScript resolution errors.