The PR supersedes the https://github.com/vercel/next.js/pull/53150, which is way too outdated, has way too many conflicts, and also heavily relies on GitHub Copilot (which makes the progress slow and tedious).
The PR uses [`json-schema-to-zod`](https://github.com/StefanTerdell/json-schema-to-zod) (instead of the GitHub Copilot) to generate the zod schema, and manually replaces all generated `z.customRefine` with my hand-written zod schema.
TODO:
- [x] Convert schema
- [x] Reduce `z.any()` usage
- [x] Create human-readable errors from the `ZodError`
- [x] Update test cases to reflect the latest error message
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The benefit of using zod over ajv:
- Easier maintenance: zod schema is straightforward to compose.
- Better typescript support: config schema now strictly reflects the `NextConfig` type.
- Smaller installation size: by replacing `ajv` and `@segment/ajv-human-errors` w/ `zod`, I am able to reduce installation size by 114 KiB.
- Better Extension: the zod error message is easy to customize.
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In the previous PR https://github.com/vercel/next.js/pull/56083, @feedthejim replaces `zod` w/ `superstruct`. `superstruct` is lightweight and fast, which makes it perfect for creating simple schemas for RSC payload. But, this also means `superstruct` has its limitations compared to `zod`:
- `superstruct`'s syntax is different, and some utilities's usage is counter-intuitive:
- `z.array(z.string()).gt(1)` vs `s.size(s.array(s.string()), 1)`
- `z.numer().gt(1)` vs `s.size(s.number(), 1)`, `s.min(s.number(), 1)`
- `z.boolean().optional().nullable()` vs `s.nullable(s.optional(z.boolean()))`
- `superstruct` has weaker TypeScript support and worse DX compared to `zod` when composing huge schema:
- `zod.ZodType + z.object()` can provide a more detailed type mismatch message on which specific property is the culprit, while `Describe + s.object()` provides almost no information at all.
- `zod`'s schema is more powerful
- `z.function()` supports `z.args()` and `z.returns()`, while `superstruct` only has `s.func()`
- zod also has Promise type `z.promise()` and intersection type `z.and()`
- `superstruct`'s error is harder to parse compared to `zod`'s `ZodError`
So in the PR, I re-introduced `zod` for `next.config.js` validation.
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