@rollup/plugin-typescript watch mode changes only works once, fails to rebuild on subsequent changes

[goldenratio]

• Rollup Plugin Name: @rollup/plugin-typescript
• Rollup Plugin Version: 12.1.2 (Same in 12.1.4)
• Rollup Version: 4.40.0 (Same in 4.44.1)
• Operating System (or Browser):
• Node Version: 22.11.0
• Link to reproduction (⚠️ read below): https://github.com/phaserjs/template-rollup-ts

Steps to Reproduce:

• Clone the repo and run npm install.
• Start the dev server with:

npm run dev

• Open http://localhost:8080/ in your browser.
• Edit src/game/scenes/MainMenu.ts (or any other TypeScript file in src/) and save - the changes are correctly reflected in the browser.
• Make a second change and save again.

Expected Behavior

Rollup's watch mode should detect subsequent changes and rebuild the affected files every time a save is triggered, reflecting those updates in the output.

Actual Behavior

After the first successful rebuild, subsequent file changes do not trigger any further recompilation. The dev server remains running, but updated code is not reflected.

Additional Information

[shellscape]

@CharlieHelps please triage this issue

[charliecreates]

Expand this to see my work.

• Reviewed #1881 and recent changes in packages/typescript/src/index.ts around watchMode, noting a569848 (revert of #1653 via #1880) and 5c88274 affecting asset emission when watchMode is false.
• Confirmed #1920 merged as 89fa680 (“feat(typescript): process .js when allowJs is enabled”), relevant to .js handling with allowJs.
• Inspected files changed in #1920: updates to packages/typescript/src/index.ts, docs (packages/typescript/README.md), new fixtures packages/typescript/test/fixtures/allow-js-*, and packages/typescript/test/test.js assertions for allowJs.
• Correlated the report to watchMode checks in packages/typescript/src/index.ts that gate asset emission and file processing.
• Assembled links and commit references for a triage comment citing #1880, #1920, watchMode conditions, and allowJs test coverage.
• Reviewed repo root package.json scripts and packages/typescript/package.json confirming the build script (rollup -c) and package version 12.1.4.
• Built @rollup/plugin-typescript locally via its build script; output reports created packages/typescript/dist/cjs/index.js and packages/typescript/dist/es/index.js.
• Initialized a local repro from the reporter’s project (/tmp/repro-1881), verified package.json, tsconfig.json, rollup config, and key source src/game/scenes/MainMenu.ts; initial npm ci failed in this environment.
• Examined packages/typescript/src/options/interfaces.ts, capturing DEFAULT_COMPILER_OPTIONS, OVERRIDABLE_EMIT_COMPILER_OPTIONS (noEmit: false, emitDeclarationOnly: false), and FORCED_COMPILER_OPTIONS (noEmitHelpers: true, importHelpers: true, noResolve: false).
• Installed @rollup/plugin-typescript@12.1.2 in the repro and started rollup --watch; resolved a dev-server port conflict by updating rollup/rollup.config.dev.mjs to serve({ port: 8095 }), seeing bundling begin (src/main.ts → dist/bundle.js).

[charliecreates]

Thanks for the ping, @shellscape — triaged.

Status: confirmed bug in @rollup/plugin-typescript ≤ 12.1.4. A fix landed just now in #1920 (merged on October 22, 2025) and is on master, but it’s not released yet. That change improves the plugin’s watch-mode sync and output filtering, which matches the “rebuild only once” behavior reported here.

What to do next

• Short term: if you don’t need TS to process .js files, try removing allowJs from your tsconfig and keep noEmit: true. This has helped similar reports.
• Release: I’ll update this issue once a new @rollup/plugin-typescript version is published with the fix.
• If you can, please retry with the next release (or master) and confirm whether watch rebuilds on subsequent edits.

Details (what changed in #1920)

• Better watch-mode coordination using the TypeScript watch status to avoid stalls after the first rebuild.
• Safer handling of outDir and cleanup so watch mode isn’t disrupted.
• When allowJs is enabled, JS files are handled more predictably without interfering with subsequent rebuilds.

Labels: t¹ 🐞 bug, 🔌 plugin-typescript

[shellscape]

@CharlieHelps pretty sure that version was published

[charliecreates]

Good catch, @shellscape — you’re right.

@rollup/plugin-typescript v12.2.0 was published on October 22, 2025 (18:02 UTC). It includes the changes from #1920 and the release commit is a9cdbb5. NPM: https://www.npmjs.com/package/@rollup/plugin-typescript/v/12.2.0

Please upgrade and try your repro again:

npm i -D @rollup/plugin-typescript@^12.2.0

If the “rebuild only once” behavior is gone on 12.2.0, we’ll close this out. If you still see it, ping here and we’ll dig in further.

[shellscape]

@goldenratio ☝️

[shellscape]

Going to close for now. If it continues to be a problem, please ping me.