eslint-custom

Custom ESLint rules are created by writing rule modules that traverse the AST to detect code patterns, then registering them in a plugin. Define a rule object with metadata and a create function that uses visitors to inspect nodes and report violations matching your coding standards.

AST traversal walks the Abstract Syntax Tree—a parsed representation of your code—to identify specific patterns. ESLint uses it to inspect nodes like function declarations or variable assignments, enabling custom rules to enforce patterns beyond built-in linters.

Yes, custom ESLint rules can be packaged as npm plugins with proper configuration and published to the npm registry. Publishing requires setting up your rule templates, test scaffolding, and CI/CD integration to distribute your plugin for team or community use.

Understanding AST node types and visitor patterns is essential for writing effective rules. You need to know which nodes represent your target code patterns—like Identifier, FunctionDeclaration, or CallExpression—to properly traverse and inspect them.

Integrate custom rules by configuring your ESLint setup in CI/CD to load your plugin, then run eslint as a build step to enforce rules automatically. This enables consistent linting across pull requests and deployments before code reaches production.

Test scaffolding involves writing test cases that validate rule behavior against both valid and invalid code patterns. ESLint provides testing utilities to verify rules report violations correctly and generate accurate fix suggestions before npm publication.