RSPack 2.0 Released

nachocodoner · May 1, 2026, 6:28am

@a4xrbj1 and @sanki92 have been working on their local projects to use Rspack 2.0, and have validated the fixes needed to run properly with 2.0.

github.com/meteor/meteor

@meteorjs/rspack: missing externalsType produces invalid JS under @rspack/core 2.0.0

opened 10:11AM - 27 Apr 26 UTC

a4xrbj1

confirmed resolved modern-build-stack

### Bug Under `@rspack/core 2.0.0` + `@meteorjs/rspack 1.0.2` (also reproduces …on `1.1.0-beta.37`), `compileWithMeteor()` externals are emitted as raw bareword identifiers in the generated bundle, which is invalid JavaScript: ```js // .meteor/local/build/programs/server/app/app.js "@bull-board/api"(module) { "use strict"; module.exports = @bull-board/api; // ← raw identifier, SyntaxError }, "geoip-country"(module) { "use strict"; module.exports = geoip-country; // ← treated as subtraction }, "meteor/accounts-base"(module) { "use strict"; module.exports = meteor/accounts-base; } ``` Server boot fails with: ``` SyntaxError: Invalid or unexpected token at new Script (node:vm:117:7) at startServerProcess (.../tools/static-assets/server/boot.js:501:17) ``` Production `meteor build` exhibits the same problem on the **client** side for `meteor/*` externals during minification, e.g.: ```js const tracker_namespaceObject = meteor/tracker; const a4xrbj1_streamy_namespaceObject = meteor/a4xrbj1:streamy; ``` → `JavaScript parse error: Expected a semicolon` from the SWC minifier. ### Root cause `@meteorjs/rspack/rspack.config.js` sets `externals: [...]` and `externalsPresets: { node: true }` but **never sets `externalsType`**. Under `@rspack/core 1.x`, the implicit default for these targets emitted `module.exports = require("name")` (commonjs). Under `@rspack/core 2.0.0`, the default appears to emit a bare-word form (`module.exports = name;` / `const X = name;`), which is only valid when the external name is a syntactically valid JS identifier. Scoped names (`@bull-board/api`), names with hyphens (`geoip-country`), and Meteor-style names with `/` and `:` (`meteor/a4xrbj1:streamy`) all break. ### Reproduction 1. Meteor 3.4 app with `@meteorjs/rspack ^1.0.2`, `@rspack/cli ^2.0.0`, `@rspack/core ^2.0.0`, `@rspack/dev-server ^2.0.1`. 2. In `rspack.config.js`: ```js const { defineConfig } = require('@meteorjs/rspack'); module.exports = defineConfig((Meteor) => ({ ...(Meteor.isServer && Meteor.compileWithMeteor(['@bull-board/api', 'geoip-country'])), })); ``` 3. \`meteor run\` → server boot crashes with `SyntaxError: Invalid or unexpected token` on first invalid identifier. ### Workaround (verified) Add \`externalsType: 'commonjs'\` to both \`Meteor.isServer\` and \`Meteor.isClient\` blocks of the user's \`rspack.config.js\`: \`\`\`js module.exports = defineConfig((Meteor) => ({ ...(Meteor.isServer && Meteor.compileWithMeteor([...])), ...(Meteor.isServer && { externalsType: 'commonjs', }), ...(Meteor.isClient && { externalsType: 'commonjs', }), })); \`\`\` Verified: dev boot clean, prod \`meteor build\` clean (server bundle 6.7 MB, client bundle 1.9 MB, all externals correctly emit \`module.exports = require(\"…\")\`). ### Proposed fix Add \`externalsType: 'commonjs'\` to the base config in \`@meteorjs/rspack/rspack.config.js\` (alongside the existing \`externalsPresets: { node: true }\` declaration around line 779), inside whatever target merge produces server bundles, and a matching one for client bundles. This restores the rspack 1.x emission semantics and is forward-compatible with rspack 2.x. ### Environment - \`@rspack/core\` 2.0.0 (released 2026-04-22) - \`@rspack/cli\` 2.0.0 - \`@rspack/dev-server\` 2.0.1 - \`@meteorjs/rspack\` 1.0.2 (also reproduces on 1.1.0-beta.37) - Meteor 3.4 - Node 22.22.0 - macOS arm64

This is one of the main issues you will hit during this transition.

To sum things up for anyone wanting to try the migration, I put together some steps based on what I did on a small skeleton app to make it work:

Upgrade Meteor to Rspack 2.0

1. Install packages

meteor npm install -D --legacy-peer-deps \
  @rspack/core@2.0.1 \
  @rspack/cli@2.0.1 \
  @rspack/dev-server@2.0.1 \
  @swc/core

--legacy-peer-deps is needed because @meteorjs/rspack still pins Rspack 1.x peers. @swc/core is required because 2.0 no longer installs it transitively.

2. Fix externals

Rspack 2.0 changed the default externalsType, which breaks scoped or Meteor-style names. Set it explicitly in the rspack.config.js file of your local project:

module.exports = defineConfig((Meteor) => ({
  externalsType: 'commonjs',
}));

3. Fix CSS

experiments.css was removed. experiments: { css: true } was part of @meteorjs/rspack defaults. Now you need to opt in per rule in the rspack.config.js file of your local project , otherwise .css files are parsed as JS:

module: {
  rules: [
    { test: /\.css$/, type: 'css/auto' },
  ],
},

Use css/auto if you have both regular CSS and .module.css.

Expect rough edges

@meteorjs/rspack last version (1.x.x / 2.x.x) predates Rspack 2.0. Other issues will likely follow the same pattern, defaults in 1.x that 2.0 removed. (Upgrading from v1 to v2 - Rspack)

Please try them out in your project and provide feedback here or in the GitHub issues section so we can track them all.

There may only be a few issues, like the one posted above and described in the Rspack 2.0 changelog. But just in case, we can move this verification work forward together.

We will address this in a future Meteor core release (Support Rspack 2.x by nachocodoner · Pull Request #14360 · meteor/meteor · GitHub), once we verify all examples and E2E tests still behave correctly and allow time for broader testing. In the meantime, it’s great that this can already move forward at the project level and that people are sharing solutions.