Migrate tooling to pnpm, Biome, and tsdown

[rosskevin]

Executive Summary

Modernizes the project's entire build and developer toolchain in a single pass: package management moves from Yarn 4 → pnpm 10, linting/formatting from ESLint + Prettier → Biome, and bundling from tsup → tsdown. The published package keeps the same shape (same .js/.d.ts entry points) and now additionally ships source that the declaration source-map resolves to. Contributors get a faster, actively-maintained toolchain; consumers see no API changes.

• For contributors: one pnpm install, one tool for lint+format (pnpm check-biome), and pnpm check to run types + lint + tests together; faster builds via Rolldown-based tsdown.
• Consumer impact: no API changes. One requirement change — the package now requires Node ≥ 24 (was ≥ 20).
• Security & quality: lockfile churn aside, the real source/config delta is small (~40 net lines); 18 tests, tsc -b, and Biome are all green.

🔗 Pull request: #34 — Migrate tooling to pnpm, Biome, and tsdown

What changed

Package manager: Yarn 4 → pnpm 10

• packageManager set to pnpm@10.33.0; yarn.lock, .yarnrc.yml, and the vendored .yarn/ release removed; pnpm-lock.yaml added.
• Single-package pnpm.onlyBuiltDependencies approves esbuild + @biomejs/biome build scripts (pnpm 10 blocks them by default).
• Scripts now pnpm-based; clean:yarn → scripts/clean-pnpm.ts; reset/release call pnpm.

Lint/format: ESLint + Prettier → Biome

• biome.jsonc extends @alienfast/biome-config/base. noUnresolvedImports is disabled (ambient .d.ts + virtual:* false positives) and useImportExtensions is disabled (this is a published NodeNext ESM lib — relative imports must keep their emitted .js specifiers, which Biome wanted to rewrite to .ts); src/__tests__/data/** fixtures are excluded.
• Removed eslint.config.mjs, .prettierignore, the prettier package.json key, and ~20 now-dead eslint-disable comments. Codebase normalized to Biome (package.json keys sorted, import type, etc.).

Bundler: tsup → tsdown

• tsdown.config.ts replaces tsup.config.ts. fixedExtension: false preserves the published .js/.d.ts contract instead of tsdown's node default of .mjs/.d.mts, so exports/main resolve unchanged.
• Dropped the ignoreDeprecations: "6.0" tsconfig hack — it only existed because tsup's DTS step injected a deprecated baseUrl; tsdown's oxc-based generator doesn't, so tsconfig.json is clean again.
• Now publishes src/ (not src/__tests__) plus index.d.ts.map so type → source navigation resolves for consumers. Dropped the vestigial rollup devDependency.

CI (.github/workflows/build.yml, setup, build-cache)

• pnpm-based setup (pnpm/action-setup + setup-node cache: pnpm, --frozen-lockfile).
• Action bumps: checkout v4 → v6, setup-node v4 → v6, cache v4 → v5, pnpm/action-setup v4 → v6.
• Added a concurrency group (cancels superseded PR runs only — never interrupts a release on main/next); replaced the repeated git fetch --unshallow --tags steps with fetch-depth: 0 on checkout.

Code Impact

Category	Added	Removed	Net
src (app)	28	33	−5
src (tests)	44	76	−32
CI (.github)	36	44	−8
Config / build / docs	197	191	+6
Subtotal (excl. lockfiles)	305	344	−39
Lockfiles + vendored .yarn	5,274	9,897	−4,623
Total	5,579	10,241	−4,662

The actual hand-written delta is tiny (~40 net lines); the large numbers are entirely the yarn.lock → pnpm-lock.yaml swap and removal of the vendored Yarn release.

Breaking Changes

• Contributors: the repo now uses pnpm. yarn install/yarn <script> no longer work — use pnpm install and pnpm <script>.
• Consumers: engines.node raised from >=20 to >=24 (drops Node 20/22). Likely a major version bump under semver.

Testing

• ✅ pnpm build — ESM + DTS (.js/.d.ts/.js.map/.d.ts.map)
• ✅ pnpm check-types (tsc -b)
• ✅ pnpm test — 18 passed
• ✅ pnpm check-biome — no findings
• ✅ npm pack --dry-run — tarball ships dist/ + src/index.ts + src/utils.ts, no test fixtures

[alienfast-build]

📦 Published PR as canary version: 4.0.0--canary.34.26896795176.0

✨ Test out this PR locally via:

npm install vite-plugin-i18next-loader@4.0.0--canary.34.26896795176.0
# or 
yarn add vite-plugin-i18next-loader@4.0.0--canary.34.26896795176.0