Bug - Uncaught (in promise) TypeError: fn is not a function

Important

This error only occurs in Routify v2.16.0. I’ve tried Routify v2.14.0, but the error doesn’t happen.

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Bug Description

I get this error when click the back button of the browser. In other case, i got this error also when navigate to another page that contain metatags helper.

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How to get this error?

1. Clone the Routify Starter template using npx degit roxiness/routify-starter routify-starter
2. Goto the project directory: cd routify-starter
3. Prepare module: pnpm i
4. Run: pnpm dev
5. Create new file with name test.svelte in src/pages
6. Put some code to that file. For me, i put this code:

<script>
  import { onMount } from 'svelte';
  import { metatags } from '@roxi/routify';

  onMount(() => {
    new Promise((resolve) => setTimeout(resolve, 3000)).then(() => {
      $metatags.title = 'Hello world';
      $metatags.description = 'Lorem ipsum dolor suila vot';
    });
  });
</script>

<h1>Hello world</h1>

1. Add a link with the destination to test.svelte page:

Example

src/pages/example/_components/RoutifyIntro.svelte

<h1>Routify Starter</h1>

To see an example app, go to 
<a href="/example">/example</a>
<a href="/test">/Test</a> // Add this

<p>To delete the example app, simply delete the ./src/pages/example folder.</p>

1. and then open your browser, and goto http://localhost:5000/.
2. Open your Browser Console (or Dev Tools).
3. Click Test link that was created before.
4. Click back button of your browser.
5. You will get this error in your browser console.

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Environment

• Routify v2.16.0
• Svelte v3.29.4

[ghostdevv]

@lamualfa From what I can tell $metatags will work fine in prod, it’s being weird with svelte-hmr so you can just manually reload effected pages till we find out exactly what causes the hmr issue and fix it. But you shouldn’t have any issues in production

Basically svelte-hmr just hot module reloads page data when changes are made, so you will see this error whenever you save a file in development mode, but to fix you can just reload the page manually

[lamualfa]

First of all, I am sorry. It seems that the description I gave is unclear. Therefore I try to summarize.

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Below v2.16.0 (this issue was not shown for this version)

The problem only occurs in metatags that use the store. Meanwhile in this version Routify doesn’t support metatags as store. So it can be concluded that the issue I created this time was not shown for this version.

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v2.16.0 and above

In this version Routify has been used metatags as a store. If you use this version and then use metatags as a store, you will get this error:

For more detail about on how to get this error i have explained above.