[Rspack][SWC] fix: add support for swc.config.ts in meteor 3.4

[sanki92]

Problem

Meteor's Rspack integration currently only supports .swcrc and swc.config.js for SWC transpiler configuration. TS developers can't use swc.config.ts for type-safe configs, which is a common pattern in modern TS projects.

Solution

Extended the SWC config loader to support .ts files:

• Added TS file handling with automatic transpilation (esbuild primary, regex fallback)
• Maintains priority order: .swcrc > swc.config.js > swc.config.ts
• Added swc.config.ts to Rspack cache dependencies for proper invalidation

Changes Made

npm-packages/meteor-rspack/lib/swc.js

• Extended getMeteorAppSwcrc() to handle .ts extensions
• Added TS transpilation with esbuild (falls back to regex if unavailable)
• Strips TS syntax: imports, types, interfaces, decorators
• Converts ES modules to CommonJS
• Updated getMeteorAppSwcConfig() to check for all three config types

npm-packages/meteor-rspack/rspack.config.js

• Added swc.config.ts path detection
• Included in build dependencies for cache invalidation

Verification

Tested with Meteor TS app:

• Only swc.config.ts present - loads correctly
• Both swc.config.js and swc.config.ts present - swc.config.js takes priority
• All three configs present - .swcrc takes priority

Example swc.config.ts:

import type { Config } from '@swc/core';

const config: Config = {
  jsc: {
    target: 'es2020',
    parser: {
      syntax: 'typescript',
      tsx: true,
      decorators: true,
    },
  },
  sourceMaps: true,
};

export default config;

Fixes #14033

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[nachocodoner]

In packages/babel-compiler/babel-compiler.js, there is also code around .swcrc/swc.config.js file usage. This is used by the Meteor bundler with modern:true in Meteor 3.3, not only by the Rspack integration that came later. It should also support swc.config.ts in the Meteor bundler, along with Meteor Rspack that you already cover.

Again, thanks to this proactivity on helping us to fix these issues.

[nachocodoner]

why do you use esbuild here?

We already benefit from @swc/core (builtin in Rspack), why don't use swc here to transform this file?

[sanki92]

Ahh you're right, my bad, didn't think to check what Rspack already had bundled. I was focused on getting the TS parsing working and just reached for esbuild. Makes way more sense to use what's already there.

And yeah, completely missed that babel-compiler needed this too. I was only testing through the Rspack path. Fixed now, but let me know if you see anything else.

[nachocodoner]

Why meteor-node-stubs was bumped here?

[sanki92]

My branch accidentally included those commits because I branched from devel, and when you changed the PR base to release-3.4.1, it picked up the extra commits.

Just cleaned it up, Should be good now, Sorry for the inconvenience :)