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perf(flags): use single dynamic import of next/headers #179

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perf(flags): use single dynamic import of next/headers #179

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8 changes: 5 additions & 3 deletions packages/flags/src/next/dedupe.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -53,10 +53,12 @@ export function dedupe<A extends Array<unknown>, T>(
): (...args: A) => Promise<T> {
const requestStore: RequestStore<T> = new WeakMap<Headers, CacheNode<T>>();

// async import required as turbopack errors in Pages Router
// when next/headers is imported at the top-level
const headersPromise = import('next/headers').then((mod) => mod.headers);
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@dferber90 dferber90 Oct 13, 2025 •
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I have not tested, but I believe this would lead to an issue in Pages Router, as we can currently do the following at the top level

const foo = dedupe(() => Math.random())

The next/headers import would originally only happen once foo is called. But with this change we would now cause the import of next/headers even if foo is not called.


const dedupedFn = async function (this: unknown, ...args: A): Promise<T> {
// async import required as turbopack errors in Pages Router
// when next/headers is imported at the top-level
const { headers } = await import('next/headers');
const headers = await headersPromise;

const h = await headers();
let cacheNode = requestStore.get(h);
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