"Intersection results could not be merged" does not mention the cause

[JoshuaKGoldberg]

Zod is great and I'm enjoying the features around intersecting/merging objects. But for .and, when the intersections results can't be merged for some reason, the error message thrown at runtime doesn't provide any details.

An error occurred.

Intersection results could not be merged

Stack Trace

ZodError: [
  {
    "code": "invalid_intersection_types",
    "path": [],
    "message": "Intersection results could not be merged"
  }
]
    at get error [as error] (file:///Users/josh/repos/dot-com/node_modules/.pnpm/zod@3.22.4/node_modules/zod/lib/index.mjs:538:31)
    at ZodIntersection.parse (file:///Users/josh/repos/dot-com/node_modules/.pnpm/zod@3.22.4/node_modules/zod/lib/index.mjs:638:22)
    at /Users/josh/repos/dot-com/src/pages/rss.xml.ts:26:48
    at Array.map (<anonymous>)

Not sure if this is a bug report or feature request, but: could the error message also include which field(s) are problematic?

Note that I'm not trying to report that the error is wrong. The error may be right - it just informative enough to explain why clearly.

Sorry that I'm not familiar enough with Zod to provide a standalone reproduction (I tried the Stackblitz Astro starter but couldn't get past TypeScript errors, amusingly). But here's how to get it on a real world project:

git clone https://github.com/JoshuaKGoldberg/dot-com
cd dot-com
git checkout 708081f # ncu-u-for-vite-5 branch
pnpm i
pnpm dev
open http://localhost:4321/rss.xml

[JacobWeisenburger]

from what I can see the problem code is this:

import { rssSchema } from "@astrojs/rss"

const rssSchemaStrict = rssSchema.and(
    z.object( {
        link: z
            .string()
            .transform( ( link ) =>
                link.replace( /^src\/content/, "" ).replace( /index.mdx$/, "" ),
            ),
        pubDate: z.date(),
        title: z.string(),
    } ),
)

it seems that rssSchema is of type ZodEffect, so that means it has a transform or something at the end of the schema which makes it not an object schema, which means it can't be used with .and()

I suggest you use the schema from here instead:
https://github.com/withastro/astro/blob/main/packages/astro-rss/src/schema.ts

If you found my answer satisfactory, please consider supporting me. Even a small amount is greatly appreciated. Thanks friend! 🙏
https://github.com/sponsors/JacobWeisenburger

[JoshuaKGoldberg]

Thanks, I appreciate the help debugging the userland issue 🙂. But, again, I'm trying to report that Zod is giving a poor error message for this issue. If I (the user) am providing bad inputs to a function then Zod should IMO give a better error message for that.

Can we move this back into an issue, please?

[JoshuaKGoldberg]

ping @JacobWeisenburger - am I missing something in thinking that the root "Zod is giving a not-helpful-enough error" issue is still unsolved?

I'm hesitant to file a second issue, but don't mind if that's the right way to get this visible.

[JacobWeisenburger]

I made it into an issue again when you asked 3 weeks ago.
#3196

[JoshuaKGoldberg]

Oh! Sorry for the ping, I'd missed that. GitHub Discussions don't have mentions added automatically the way issues and PRs do. Thanks!