Build issue for scheduler import, with Vite

[ajmas]

The documentation indicates the following for the import for the scheduler:

import { IntervalBasedCronScheduler as scheduler } from 'cron-schedule/schedulers/interval-based.js'

Though when I do this in VS Code it says it cant' find it. The following works though, but then breaks in execution of the app:

import { IntervalBasedCronScheduler as scheduler } from 'cron-schedule/dist/schedulers/interval-based.js'

Originally I though this was a documentation issue, but now I am wondering whether the packaging has some issues, since if I use cron-schedule/schedulers/interval-based.js dev runtime works, build build time fails.

Error output:

src/views/MagicScreen.vue:45:54 - error TS2307: Cannot find module 'cron-schedule/schedulers/timer-based.js' or its corresponding type declarations.

45 import { TimerBasedCronScheduler as scheduler } from 'cron-schedule/schedulers/timer-based.js';
                                                         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

My import is presented as follows in my Vue file:

import { parseCronExpression } from 'cron-schedule';
import { TimerBasedCronScheduler as scheduler } from 'cron-schedule/schedulers/timer-based.js';

I am using Vite 3.2.3 for packaging.

Looking at issue #284, but yarn add cron-schedule@4.0.0-next.3 -S didn't change anything.

[P4sca1]

Which version of cron-schedule, node, and typescript are you using?

[ajmas]

My last try was with 4.0.0-next.3, though I’ll double check to see what actually got installed.

[ajmas]

I have created a sample project which also shows the same issue:

https://github.com/ajmas/vue-cron-sample

The cron-schedue import is in src/components/HelloWorld.vue.

You can see the behaviour on npm run build.

Hopefully this helps you investigate.

[ajmas]

So investigation shows that Typescript doesn't deal with package exports too well.

What I ended up doing in a local checkout of cron-schedule is to export the schedulers via the default export:

import  { TimerBasedCronScheduler } from './schedulers/timer-based.js'
import  { IntervalBasedCronScheduler } from './schedulers/interval-based.js'

export * from './cron-parser.js'
export * from './cron.js'

export { TimerBasedCronScheduler, IntervalBasedCronScheduler }

With my Vite based Vue project, only the TimerBasedCronScheduler scheduler (the one I was using) ended up in the generated bundles, with IntervalBasedCronScheduler being excluded. This meant the change in approach didn't leave me with bundled unused dependencies.

[P4sca1]

Have you tried "moduleResolution": "node16" in your tsconfig.json, and which version of typescript are you using?

[ajmas]

I tried a lot of things, include that. It creates other breakages.

BTW If anyone else sees this issue and can show by demonstration of a change to https://github.com/ajmas/vue-cron-sample makes this work, then I would be interested to know what you did.

Short term I am tempted to fork this project, and make the indicated changes, since I can't use it otherwise. Once Typescript finally addresses this then I can look to going back to the main fork. Right now this is a blocker in our project. We have already spent too may hours on this, so we are opting for the easy way out.

[ajmas]

I just saw that @intlify/unplugin-vue-i18n has a package export that works, suggesting the issue may be something to do with how things are packaged. I am able to import @intlify/unplugin-vue-i18n/vite. The export does look a little different:

  "./vite": {
      "require": "./lib/vite.cjs",
      "import": "./lib/vite.mjs",
      "types": "./vite.d.ts"
 }

I'll need to explore some more here, to see how it creates its distributables and then see if I can apply the same here?

Following the recipe here provided a working solution:

https://www.sensedeep.com/blog/posts/2021/how-to-create-single-source-npm-module.html

I'll create a PR for you to review.

[ntsd]

I got this problem also this pr will fix #295

[P4sca1]

If you’re using Node 12 or 14, you should use --moduleResolution node16. The features added to 16 have fully or mostly been backported to 12 and 14.
--moduleResolution node is for Node 11 and older. Its name is currently bad. We plan to rename it accordingly.

microsoft/TypeScript#50794

In order to use this package, you need to use moduleResolution node16 or nodenext.