Implement an Upgrader for migrating from Svelte 4 to 5

[annaghi]

Describe the problem

With the upcoming release of Svelte 5, in order to use the new features a huge amount of manual refactoring would be needed on an existing code base.

Describe the proposed solution

It would be nice to have an upgrader tool, which would:

• Analyze the existing Svelte (3) 4 codebase.
• Automatically refactor the code to be compatible with Svelte 5.
• Provide a report outlining what changes were made and if any manual interventions are needed.

Alternatives considered

• Maintaining Backward Compatibility
• Not Maintaining Backward Compatibility

Importance

nice to have

[jorri11]

From https://svelte.dev/blog/runes : "Even though we're changing how things work under the hood, Svelte 5 should be a drop-in replacement for almost everyone. The new features are opt-in — your existing components will continue to work." So looks like there wont be breaking changes (?)

[annaghi]

Thanks, @jorri11 updated my problem description according to that.