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fix: unstable_cache undefined cache #339

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Merged
james-elicx merged 1 commit into from
Mar 8, 2026
+38 −2
Merged

fix: unstable_cache undefined cache #339

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19 changes: 17 additions & 2 deletions packages/vinext/src/shims/cache.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -581,6 +581,21 @@ const _UNSTABLE_CACHE_ALS_KEY = Symbol.for("vinext.unstableCache.als");
const _unstableCacheAls = (
(_g[_UNSTABLE_CACHE_ALS_KEY] ??= new AsyncLocalStorage<boolean>()) as AsyncLocalStorage<boolean>
);
const UNSTABLE_CACHE_UNDEFINED_SENTINEL = "__vinext_unstable_cache_undefined__";

function serializeUnstableCacheResult(value: unknown): string {
return value === undefined
? UNSTABLE_CACHE_UNDEFINED_SENTINEL
: JSON.stringify(value);
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@ask-bonk ask-bonk bot Mar 8, 2026

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Nit: JSON.stringify also returns undefined (the JS value) for top-level function and Symbol values. Those are equally un-cacheable with the current code path. Not something that needs fixing in this PR — just noting for awareness that the same class of bug exists for those types. In practice nobody caches functions, so this is fine.

}

function deserializeUnstableCacheResult(body: string): unknown {
if (body === UNSTABLE_CACHE_UNDEFINED_SENTINEL) {
return undefined;
}

return JSON.parse(body);
}

/**
* Check if the current execution context is inside an unstable_cache() callback.
Expand Down Expand Up @@ -625,7 +640,7 @@ export function unstable_cache<T extends (...args: any[]) => Promise<any>>(
});
if (existing?.value && existing.value.kind === "FETCH" && existing.cacheState !== "stale") {
try {
return JSON.parse(existing.value.data.body);
return deserializeUnstableCacheResult(existing.value.data.body);
} catch {
// Corrupted entry, fall through to re-fetch
}
Expand All @@ -641,7 +656,7 @@ export function unstable_cache<T extends (...args: any[]) => Promise<any>>(
kind: "FETCH",
data: {
headers: {},
body: JSON.stringify(result),
body: serializeUnstableCacheResult(result),
url: cacheKey,
},
tags,
Expand Down
21 changes: 21 additions & 0 deletions tests/shims.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -733,6 +733,27 @@ describe("next/cache shim", () => {
setCacheHandler(new MemoryCacheHandler());
});

it("unstable_cache caches undefined results", async () => {
const { unstable_cache, setCacheHandler, MemoryCacheHandler } =
await import("../packages/vinext/src/shims/cache.js");

setCacheHandler(new MemoryCacheHandler());

let callCount = 0;
const cached = unstable_cache(async () => {
callCount++;
return undefined;
}, ["undefined-result-test"]);

await expect(cached()).resolves.toBeUndefined();
expect(callCount).toBe(1);

await expect(cached()).resolves.toBeUndefined();
expect(callCount).toBe(1);

setCacheHandler(new MemoryCacheHandler());
});

it("revalidateTag invalidates cached entries", async () => {
const {
unstable_cache,
Expand Down
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