Type import with same name as variable causes migration error

[brunnerh]

Describe the bug

Type imports can have the same name as a local variable, but this causes errors when using the "Migrate Component to Svelte 5" command.

There also is a secondary issue that one can get false positive errors from the command if the installed Svelte version was to old/non-existent when the command was first called on the file. So instead of getting a @migration-task Error ... in the code, an error notification pops up that claims that the Svelte version does not support migration, even though it works on other components.

Reproduction

// test.ts
export type Thing = string;

<script lang="ts">
    import type { Thing } from './test';

    export let Thing: Thing = 'hi';
</script>

{Thing}

(Import is important, a local type definition does not cause the error.)

Expected behaviour

Migration works.

System Info

• OS: Win 11
• IDE: VS Code 1.121.0
• Extension: 110.0.0

Which package is the issue about?

Svelte for VS Code extension

Additional Information, eg. Screenshots

No response

[jasonlyu123]

This is not allowed under Svelte5's native TypeScript support. The "Identifier 'Thing' has already been declared" error is from the svelte compiler. I also can't reproduce the issue with the secondary issue. Maybe you just need to restart your editor after you updated your Svelte version?

[brunnerh]

This is not allowed under Svelte5's native TypeScript support.

We are using a preprocessor anyway because of style preprocessing, so the code works.

I also can't reproduce the issue with the secondary issue. Maybe you just need to restart your editor after you updated your Svelte version?

Restarting the editor or reloading extensions obviously fixes the issue, the main problem is that you get a misleading & unhelpful error unless you do so.

[jasonlyu123]

Type imports can have the same name as a local variable, but this causes errors when using the "Migrate Component to Svelte 5" command.

What exactly is the error you mentioned here? Is it the error I mentioned? What I see is that it prints @migration-task Error if it's the same as what you have seen. It's not something that can be fixed on the language-server side.

About the error notification, the language server will only show it when the Svelte compiler doesn't have the migrate function. It's not a generic message when a runtime error occurs. So it's not really "false positive errors". Do you have an idea on how to improve the error message? Is it better to mention that you might need to restart the editor? I am not sure it makes sense to watch the file-system update for the Svelte compiler, because it's not that often people have a big upgrade. And another problem is that it is cached by Node.js's module loader.

[brunnerh]

What exactly is the error you mentioned here? Is it the error I mentioned? What I see is that it prints @migration-task Error if it's the same as what you have seen. It's not something that can be fixed on the language-server side.

Yes, issue maybe should be transferred to the main repository.

About the error notification...

If it is a module caching issue, it is a bit surprising that it behaves differently between components, i.e. I could migrate files where I did not try to migrate before the installation of the new Svelte version in the same VS Code instance. I would have expected it to either be coupled to the language server instance or the VS Code extensions process.

As for the message, maybe include a note (and possibly a button) about the reload.

Your installed Svelte version does not support migration.
Reloading the window is required after installing a new version.
[Reload Window]

Where the button executes workbench.action.reloadWindow.

If the migration is performed by the language server and a restart (svelte.restartLanguageServer) of that would be sufficient, that would be preferable to a full window reload.