oxlint-plugin-ts-no-assert

Disallow TypeScript type assertions (as, angle-bracket <Type>, and non-null !) — ported from eslint-plugin-no-type-assertion to Oxlint's JS plugin API. Also works with ESLint flat config via the bundled eslintCompatPlugin wrapper.

Requirements

• Oxlint >= 1.0.0 (requires jsPlugins support)
• Node.js >= 18

Installation

npm add -D oxlint-plugin-ts-no-assert
# or
bun add -d oxlint-plugin-ts-no-assert

Usage with Oxlint

Add the plugin to jsPlugins and enable the rule:

// .oxlintrc.json
{
  "jsPlugins": ["./node_modules/oxlint-plugin-ts-no-assert/dist/index.js"],
  "rules": {
    "oxlint-plugin-ts-no-assert/no-type-assertion": "error"
  }
}

Usage with ESLint

// eslint.config.mjs
import tsNoAssertPlugin from "oxlint-plugin-ts-no-assert/dist/index.js";

export default [
  {
    plugins: { "no-type-assertion": tsNoAssertPlugin },
    rules: tsNoAssertPlugin.configs.recommended.rules,
  },
];

Rules

no-type-assertion/no-type-assertion

Disallows all three forms of TypeScript type assertion.

Forbidden:

const x = value as MyType;     // ❌ Do not use `as` operator for type assertion
const x = <MyType>value;       // ❌ Do not use type assertion (angle-bracket)
const x = maybeNull!;          // ❌ Do not use non-null assertion operator

Allowed — safe widening that TypeScript itself endorses:

const x = value as unknown;    // ✅ widening to unknown is safe
const x = value as const;      // ✅ const assertion
const x = <unknown>value;      // ✅
const x = <const>value;        // ✅

Note on angle-bracket syntax: TypeScript disallows <Type>value in .tsx files because it is syntactically ambiguous with JSX. The angleBracketAssertion diagnostic will only appear in plain .ts files.

| Rule | Description | Recommended | |---|---|---| | no-type-assertion | Disallow as, <Type>, and ! type assertions (except as const / as unknown) | error |

License

MIT