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(refactor/react): Memoize ComponentScope unique value with useState to ensure referential stability. #73

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(refactor/react): Memoize ComponentScope unique value with useState to ensure referential stability. #73

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18 changes: 11 additions & 7 deletions src/react/useScopes.tsx
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Original file line number Diff line number Diff line change
@@ -1,4 +1,4 @@
import { useContext, useEffect, useMemo, useRef, useState } from "react";
import { useContext, useEffect, useMemo, useState } from "react";
import { MoleculeScopeOptions } from "../shared/MoleculeScopeOptions";
import { dstream } from "../shared/getDownstreamScopes";
import { ComponentScope, ScopeTuple } from "../vanilla";
Expand Down Expand Up @@ -56,13 +56,17 @@ export function useScopes(
export function useScopeTuplesRaw(options?: MoleculeScopeOptions) {
const parentScopes = useContext(ScopeContext);

const generatedValue = useMemo(
() => new Error("Do not use this scope value. It is a placeholder only."),
[],
);
// `useState` instead of `useMemo`, so React cannot discard the cached value.
const [componentScopeTuple] = useState(() => {
// We only care about referential stability, so this value can be any object.
const generatedValue = new Error(
"Do not use this scope value. It is a placeholder only.",
);

const componentScopeTuple = useRef([ComponentScope, generatedValue] as const)
.current as ScopeTuple<unknown>;
return [ComponentScope, generatedValue] as ScopeTuple<unknown>;
});

const generatedValue = componentScopeTuple[1];

const inputTuples: AnyScopeTuple[] = (() => {
if (!options) return [...parentScopes, componentScopeTuple];
Expand Down