Add support for specifying SWC's env option in Next.js configuration

[sue71]

Goals

Allow users to specify SWC's env option

Non-Goals

n/a

Background

The original SWC supports options equivalent to babel's preset-env and allows for specifying the useBuiltIns equivalent option under mode.

https://swc.rs/docs/configuration/swcrc#supported-browsers

However, Next.js sets SWC options internally, preventing framework users from configuring it directly. This constraint prevents me from safely using polyfills with the usage option and migrating to SWC.

Proposal

There are several options, but for now, I prefer option 2.

Option 1. Enable specifying SWC options via .swcrc file

While I believe this is the most elegant solution, supporting .swcrc could have some impact, making it difficult to address immediately. There are some related issues on this matter, but no progress has been seen on them yet.

refs

• SWC: using custom config in a root directory #30413
• allow user to configure .swcrc #30940

Option 2. Add experimental support for swcEnv options and make them configurable in the next.config

Add the swcEnv or swcEnvMode option as an experimental feature and pass the option to the following code.

https://github.com/vercel/next.js/blob/canary/packages/next/src/build/swc/options.ts#L515

This change is minimal and has only a minor impact on existing users.

[Daniel3711997]

Any news here?