Introduction

TypeScript catches a lot in an implement app, because there is no template language for it to lose sight of — a component is a function call and its props are an object literal. But some mistakes are the right shape and still wrong. aria-lable is a perfectly good key on a props object. A subscribe whose unsubscribe you drop on the floor type-checks exactly like one you keep.

@implementjs/eslint is a small set of rules for those. It is written against ESLint's plugin API, and it runs under either linter — ESLint, or oxlint through oxlint's ESLint-compatible plugin support. One package, one set of rules, whichever linter you already have.

Set it up in a few lines of config, and read how the rules see your code for what they can and cannot tell you.

The rules

Six of them are about implement itself — signals that get read wrong, subscriptions that outlive their owner, markup that renders once when it meant to stay live:

Rule	Recommended	Catches
no-hanging-unsubscribe	error	a subscription to a longer-lived signal whose unsubscribe is discarded
prefer-effect	warn	an ImplementLifecycle that exists only to own a watch
no-signal-condition	error	a signal tested for truth, which is always true
no-signal-collection	warn	a Set or Map inside a signal() rather than a reactive collection
prefer-foreach	error	.get().map() rendering a list that will never update
no-html	error	every use of Html, which does not sanitize

The other five check the accessibility props you write by hand, against the WAI-ARIA 1.2 vocabulary:

Rule	Recommended	Catches
valid-aria	error	a misspelled aria-* key, or a value the attribute does not permit
valid-role	error	a misspelled or abstract role
role-has-required-aria-props	error	a role missing the property it is incomplete without
role-supports-aria-props	error	an aria-* property the role ignores
no-redundant-roles	warn	a role an element already has