custom resolve alias not available in .paths.js file

[jcbhmr]

Describe the bug

when using a [slug].md and [slug].paths.js file for dynamic routes the [slug].paths.js file doesnt seem to get access to the magic resolve.alias["alias-goes-here"] = "/the/actual/file.js" stuff.

Reproduction

https://stackblitz.com/edit/vite-lt2rg5?file=docs%2F.vitepress%2Fconfig.ts,docs%2F.vitepress%2Fhello.js,docs%2F[slug].paths.js

  vite: {
    clearScreen: false,
    resolve: {
      alias: {
        '~hello': fileURLToPath(new URL('./hello.js', import.meta.url)),
      },
    },
  },

import hello from '~hello';

export default {
  paths() {
    return [{ params: { slug: hello } }];
  },
};

failed to load config from /home/projects/vite-lt2rg5/docs/[slug].paths.js
Invalid paths file export in /home/projects/vite-lt2rg5/docs/[slug].paths.js. Expects default export of an object with a "paths" property.

if i remove the import hello from "~hello" line the error goes away

// import hello from '~hello';

export default {
  paths() {
    return [{ params: { slug: 'hello' } }];
  },
};

Expected behavior

i should be able to import hello from "~hello" and have it work, right?

System Info

System:
    OS: Linux 5.0 undefined
    CPU: (4) x64 Intel(R) Core(TM) i9-9880H CPU @ 2.30GHz
    Memory: 0 Bytes / 0 Bytes
    Shell: 1.0 - /bin/jsh
  Binaries:
    Node: 18.18.0 - /usr/local/bin/node
    Yarn: 1.22.19 - /usr/local/bin/yarn
    npm: 9.4.2 - /usr/local/bin/npm
    pnpm: 8.9.2 - /usr/local/bin/pnpm
  npmPackages:
    vitepress: latest => 1.0.0-rc.23

Additional context

Validations

• Check if you're on the latest VitePress version.
• Follow our Code of Conduct
• Read the docs.
• Check that there isn't already an issue that reports the same bug to avoid creating a duplicate.

[jcbhmr]

i think the issue comes from this:

vitepress/src/node/plugins/dynamicRoutesPlugin.ts

Line 186 in a31e143

mod = (await loadConfigFromFile({} as any, pathsFile)) as RouteModule

being a completely new Vite "load like vite.config.js" operation which doesn't inherit the existing Vite options (including resolve.alias)

is ssrLoadModule() a way to do the "load with ts and esm support" operation? idk https://vitejs.dev/guide/ssr.html#:~:text=%3D%20await%20vite.-,ssrLoadModule,-(%27/src/entry

[brc-dd]

server isn't there in build, so can't do server.ssrLoadModule. I'm not sure if there is any simple solution to this.

There was some discussion at #2289. But the solution, until vite itself lands something like vite-node or vavite into the core, is to not use aliases in data/path loader files.

[vincesp]

Hint: There is native support for this in Node itself. This works everywhere, including in data/path loader files:
https://nodejs.org/api/packages.html#subpath-imports

package.json:

  "imports": {
    "#theme/*": "./docs/.vitepress/theme/*"
  }

[slug].paths.js:

import hello from '#theme/hello.js'

[jcbhmr]

this is a great trick! it doesn't work so well for my usecase where the import { thing } from "~hello" comes from a vite plugin that adds a resolve alias. 😢

[babakfp]

Hint: There is native support for this in Node itself. This works everywhere, including in data/path loader files: https://nodejs.org/api/packages.html#subpath-imports

package.json:

  "imports": {
    "#theme/*": "./docs/.vitepress/theme/*"
  }

[slug].paths.js:

import hello from '#theme/hello.js'

This solved my issue, THANKS ❤️
#3309
Sending this ^^^ here so people may have the same issue.