export const metadata = { title: route-params-must-be-defined - ESLint plugin rules, }

{metadata.title}

This rule requires properties accessed on req.params in an API route handler to correspond to a [param] folder in the route path.

Severity

error. This rule is enabled in the recommended preset.

What it Targets

This rule targets route.ts and route.js files in your project's src/api directory. It reports access to a req.params property that has no matching [param] folder in the route path.

The following code is reported by the rule, since the route has no foo parameter:

export const GET = (req, res) => {
  const x = req.params.foo
}

Instead, access a parameter defined by a [param] folder:

export const GET = (req, res) => {
  const x = req.params.id
}

Why it's Important

A route parameter is only available on req.params when a [param] folder defines it in the route path. Accessing an undefined parameter returns undefined, which often points to a typo or a missing folder.

Learn more in the Route Parameters documentation.

Fixable

This rule isn't auto-fixable.