no-new-instance-in-use-memo

Reports configured new expressions inside useMemo callbacks, including traced local helper calls.

Rule details Problem

By default, the rule reports new Instance(...) inside useMemo. It also follows local helper functions called from the memo callback, up to maxHelperTraceDepth, so a helper that creates an instance is still reported.

The rule only checks useMemo imported from the configured React environment. environment: "roblox-ts" watches @rbxts/react, and environment: "standard" watches react.

What maxHelperTraceDepth does

0 only checks code written directly inside the useMemo callback. The default is 4, which also traces a few helper calls.

Examples

Incorrect

Constructor inside useMemo

import { useMemo } from "@rbxts/react";

const model = useMemo(() => {
  return new Instance("Model");
}, []);

Also incorrect

Helper traced from useMemo

import { useMemo } from "@rbxts/react";

function createModel() {
  return new Instance("Model");
}

const model = useMemo(() => createModel(), []);

Correct

Reuse or create outside the memo callback

import { useMemo } from "@rbxts/react";

const model = new Instance("Model");

const memoizedModel = useMemo(() => model, []);

Options

Option	Type	Default	Notes
constructors	string[]	["Instance"]	Constructor names to report.
environment	"roblox-ts" | "standard"	"roblox-ts"	Picks @rbxts/react or react imports.
maxHelperTraceDepth	integer	4	Helper-call depth to trace from the memo callback. 0 disables helper tracing.

import ceaseNonsense from "eslint-plugin-cease-nonsense";

export default [
  {
    plugins: {
      "cease-nonsense": ceaseNonsense,
    },
    rules: {
      "cease-nonsense/no-new-instance-in-use-memo": [
        "error",
        {
          constructors: ["Instance", "Vector3"],
          environment: "roblox-ts",
          maxHelperTraceDepth: 2,
        },
      ],
    },
  },
];

Related rules

no-unused-use-memo Disallows useMemo calls that are only used for side effects

no-useless-use-effect Reports effects that are not syncing with anything external