nextjs - 💡(How to fix) Fix Turbopack prod minifier breaks citeproc with Chicago author-date bibliography [1 participants]

Link to the code that reproduces this issue

https://github.com/dandyling/citeproc-chicago-author-date-turbopack-build-repro

To Reproduce

1. Clone the reproduction repo:

git clone https://github.com/dandyling/citeproc-chicago-author-date-turbopack-build-repro.git
cd citeproc-chicago-author-date-turbopack-build-repro

1. Install dependencies:

npm install

1. Confirm that dev mode works:

npm dev

Visit http://localhost:3000 The page renders and the bibliography is produced without error.

1. Build and run in production:

npm build
npm start

Visit http://localhost:3000

1. Observe that the prod build throws:

   TypeError: Cannot read properties of null (reading '2') at f.Engine.Fun.y [as page_mangler] at f.Engine.processNumber at f.getCite at f.getSortKeys at f.Registry.setsortkeys at f.Engine.updateItems at o.a [as format]

2. As a control, disable the Turbopack minifier in next.config.ts:

experimental: {
   turbopackMinify: false,
}

Then re-run:

npm build
npm start

Now the page renders correctly in production.

Current vs. Expected behavior

Current behavior

In production with the Turbopack minifier enabled (default for Next.js 16), loading a Chicago author-date CSL style and formatting a bibliography entry that has a page field causes citeproc-js to throw:

TypeError: Cannot read properties of null (reading '2') at f.Engine.Fun.y [as page_mangler] at f.Engine.processNumber at f.getCite at f.getSortKeys at f.Registry.setsortkeys at f.Engine.updateItems at o.a [as format]

This only happens in the prod build; next dev works fine.

The repro is a minimal App Router project whose app/page.tsx is a single client component that, on mount:

1. Fetches public/chicago-author-date.csl (official CSL XML from citation-style-language/styles).
2. Registers it via plugins.config.get('@csl').templates.add('chicago-author-date', xml).
3. Constructs a Cite from one CSL JSON entry that has page: '45-67'.
4. Calls cite.format('bibliography', { template: 'chicago-author-date', ... }).

With the default Turbopack minifier in production, step 4 crashes with the stack above.

Expected behavior

The production build should behave like next dev:

• citeproc-js should not throw.
• The page should render the bibliography HTML for the single entry with the page field, using the Chicago author-date CSL style.
• Disabling experimental.turbopackMinify should not be required to avoid the error.

Provide environment information

next: 16.1.7
react: 19.2.3
node: 20.20.0

Additional relevant packages:
- @citation-js/core: 0.7.14
- @citation-js/plugin-csl: 0.7.14
- citeproc: 2.4.63

Which area(s) are affected? (Select all that apply)

Turbopack

Which stage(s) are affected? (Select all that apply)

next build (local), Vercel (Deployed)

Additional context

• Repro repo: https://github.com/dandyling/citeproc-chicago-author-date-turbopack-build-repro
• The issue appears to be specific to the Turbopack prod minifier; turning it off via experimental.turbopackMinify: false makes the same code work in production.
• The CSL style file public/chicago-author-date.csl is the official Chicago author-date style copied verbatim from the citation-style-language/styles repository.
• The bug only reproduces when the CSL JSON entry includes a page field like page: '45-67', which triggers citeproc-js's page_mangler.
• Environment: Node 20.20.0, Next.js 16.1.7, React 19.2.3, @citation-js/core 0.7.14, @citation-js/plugin-csl 0.7.14, citeproc 2.4.63.