cloudflare/vinext

Build failure: Babel flowtype page compilation not supported

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#1,506 opened on May 22, 2026

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Description

This issue was created by an agent analysing CI failures from the Next.js Deploy Suite (vinext main vs Next.js v16.2.6, 2026-05-22).

Problem

Pages using flowtype syntax (compiled via Babel + @babel/preset-flow) fail the vinext build with Custom deploy script failed: undefined (1). The Vite/Rolldown pipeline does not run user Babel configuration for these files.

Babel + preset-flow page fails to build

Estimated Impact

~1 test failures across the deploy suite.

Affected Test Suites

  • test/e2e/babel/index.test.ts

Recommendation

  1. Reproduce first in vinext's own test suite. Add a page using flow syntax with a .babelrc enabling @babel/preset-flow, confirm the build fails.

  2. Decide on Babel support. Either add an opt-in Babel-compatibility loader for files matched by user .babelrc, or document that Babel is not portable and convert the fixture to TS.

Contributor guide

Research direction
Reproduce the build failure by adding a test page with flow syntax and a .babelrc. Then investigate how to add a Babel compatibility loader or document the limitation.
Tech stack
typescriptjavascriptvite
Domain
frontendbuild system
Issue type
Bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
Half day
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
GitJavaScript
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
65