[RFC] Discontinue Vue2 support in SB8

[shilman]

Summary

Vue2 will reach End of Life (EOL) on December 31, 2023. As such, we propose to:

1. Deprecate Vue2 support in Storybook 7.6 to warn to existing Storybook Vue2 users.
2. Drop Vue2 support in Storybook 8.0, which will be released in 2024Q1.

Problem Statement

Storybook currently supports Vue2 (@storybook/vue) and Vue3 (@storybook/vue3). They are separate packages and codebases, so it is a maintenance burden for the team to support both versions. Our telemetry shows ~12% of active Vue storybooks are Vue2, i.e. ~78% are Vue3.

Implementation

We propose to deprecate our Vue2 packages in 7.6 and remove them completely in 8.0 as a breaking change. These packages include @storybook/vue, @storybook/vue-vite, @storybook/vue-webpack5. Vue3 will continue to be supported via @storybook/vue3, @storybook/vue3-vite, @storybook/vue3-webpack5.

This solution has the following benefits:

• Simplify the Storybook codebase by removing several packages
• Reduce our maintenance and support overhead and allow us to focus on Vue3
• Help encourage users to move to Vue3, which the Vue core team's intent by EOL'ing Vue2

Vue2 users who cannot migrate to Vue3 can continue to use Storybook 7.x.

Unresolved Questions

We are putting out this RFC for feedback. If you are a Vue2 user who hopes to migrate to Storybook 8 when it is released, please make a case for why we should continue to support Vue2 when the core team is not supporting it themselves. Or if you think there is a better way to go about EOL'ing Storybook's Vue2 support, we are also open to suggestions. Thank you!