fix(plugin-legacy): wrap chunks in IIFE

[avocadowastaken]

Description

Solving the same problem as #2972, but contains tests and source map support (sorry for the duplicate, but original PR is not changed since the April and this bug block migration of the large codebase from the CRA to Vite).

If someone comes from google, it solves global scope pollution issues like:

• Can't create duplicate variable: '_excludes', redeclaration of const _excludes or Identifier '_excludes' has already been declared errors caused by @babel/plugin-desctructuring (example)

• Issues with styled-components or emotion caused by @babel/plugin-transform-template-literals (example)

What is the purpose of this pull request?

• Bug fix
• New Feature
• Documentation update
• Other

Before submitting the PR, please make sure you do the following

• Read the Contributing Guidelines.
• Read the Pull Request Guidelines and follow the Commit Convention.
• Check that there isn't already a PR that solves the problem the same way to avoid creating a duplicate.
• Provide a description in this PR that addresses what the PR is solving, or reference the issue that it solves (e.g. fixes #123).
• Ideally, include relevant tests that fail without this PR but pass with it.

[antfu]

I think we would need to keep the map from babel, and that's why the original PR get blocked since MagicString does not take source map input, while I am not familiar with babel transforming to support sourcemap

[avocadowastaken]

@antfu thanks for the quick review! I've changed implementation to use babel plugin for transformations, so source map behavior should not change

[antfu]

Thanks!

[avocadowastaken]

@antfu @patak-js sorry if I'm being annoying, but is there any release plan for that fix?

[patak-cat]

We'll do a release on Monday or Tuesday including this fix

[patak-cat]

@umidbekk @vitejs/plugin-legacy@1.4.2 has been released including this PR