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no-reject

Disallow Promise.reject(...).

Targeted pattern scope​

This rule targets CallExpression nodes matching Promise.reject(...).

What this rule reports​

  • Calls to Promise.reject(...)

Why this rule exists​

In immutable/functional error handling, explicit error values are often preferred over rejected promise control flow.

❌ Incorrect​

return Promise.reject(new Error("boom"));

✅ Correct​

return { ok: false, error: "boom" };

Additional examples​

// ❌ Rejecting promise for expected validation outcome
const loadUser = async (id: string) => {
    if (!id) {
        return Promise.reject(new Error("Missing user id"));
    }
    return fetchUser(id);
};

// ✅ Return a value-level failure object
const loadUser = async (id: string) => {
    if (!id) {
        return { ok: false, error: "Missing user id" };
    }
    return { ok: true, value: await fetchUser(id) };
};

ESLint flat config example​

import immutable from "eslint-plugin-immutable-2";

export default [
    {
        files: ["**/*.{js,mjs,cjs,ts,mts,cts,tsx}"],
        plugins: { immutable },
        rules: {
            "immutable/no-reject": "error",
        },
    },
];

When not to use it​

Keep Promise.reject if your APIs intentionally model failures as rejected promises (for example, compatibility layers around fetch wrappers or public SDKs that consumers already handle with .catch). In that case, document the error contract and apply this rule only to internal logic.

Rule catalog ID: R909

Further reading​