`unstable_cache` doesn't serialize non-primitive data types

### Link to the code that reproduces this issue https://github.com/devjmetivier/next-unstable-cache-args-serialization ### To Reproduce 1. Open homepage 2. Change sort order with input 3. See request cache behavior ### Current vs. Expected behavior Cache doesn't work (as expected) because passing arguments to `unstable_cache` of any non-JSON serializable data type (Map, in this example) results in the same deterministic output. <img width="363" alt="Image" src="https://github.com/user-attachments/assets/2403c912-de84-4cd3-8f1b-7bfa22f535b7" /> ### Provide environment information ```bash Operating System: Platform: darwin Arch: arm64 Version: Darwin Kernel Version 24.1.0: Thu Nov 14 18:19:02 PST 2024; root:xnu-11215.41.3~13/RELEASE_ARM64_T8132 Available memory (MB): 32768 Available CPU cores: 10 Binaries: Node: 22.12.0 npm: 10.9.0 Yarn: 1.22.22 pnpm: 9.15.3 Relevant Packages: next: 15.2.0-canary.16 // Latest available version is detected (15.2.0-canary.16). eslint-config-next: N/A react: 19.0.0 react-dom: 19.0.0 typescript: 5.7.3 Next.js Config: output: N/A ``` ### Which area(s) are affected? (Select all that apply) Runtime, Not sure ### Which stage(s) are affected? (Select all that apply) next dev (local), next build (local), next start (local), Vercel (Deployed) ### Additional context I understand that `unstable_cache` is intended to handle any work inside the function, but I'm encountering an issue when passing iterables like Maps and Sets. These data structures aren't serializable, so their contents can't be cached, forcing me to either change the data type or manually serialize/deserialize the values. It would be helpful if unstable_cache could support these types (iterables) more seamlessly. Here's where I can see these arguments being dealt with in Next.js: https://github.com/vercel/next.js/blob/3f3f4bc78145e1bb271781aabd595758dd0686a9/packages/next/src/server/web/spec-extension/unstable-cache.ts#L138-L144