Summary

@babel/preset-env currently throws a hard error when the removed bugfixes option is passed. This turns a harmless leftover config key into a build-breaking crash. This PR downgrades it to a console.warn, as suggested in the issue thread.

Background

bugfixes was removed in Babel 8 because bugfix plugins are now always enabled, so the option is a no-op. But configs carried over from Babel 7 (or shared presets that still set it) commonly include bugfixes: true. On Babel 8 those configs fail outright at normalizeOptions:

v.invariant(
  !Object.hasOwn(opts, "bugfixes"),
  "The 'bugfixes' option has been removed, ...",
);

Since the option no longer does anything, a hard error is stricter than necessary. In the issue, a core maintainer noted that downgrading it to a console.warn is reasonable, matching how the corejs-without-useBuiltIns case is already handled in this same file.

Fix

When bugfixes is present, emit a console.warn (same message, same newline-wrapped WARNING (@babel/preset-env): style as the existing corejs warning) instead of throwing.

There is one subtlety: bugfixes is not in TopLevelOptions, and the very next line calls v.validateTopLevelOptions, which throws on any unknown top-level key. So simply swapping the invariant for a warning would still crash. To avoid that, the option is stripped from a shallow copy of the input before validation runs. The caller's original options object is left untouched (only the local reference is reassigned), and configs that never pass bugfixes are completely unaffected.

Testing

Added a focused case to packages/babel-preset-env/test/normalize-options.skip-bundled.js that spies on console.warn and asserts: passing bugfixes: true/false no longer throws, a warning mentioning bugfixes is emitted, the caller's options object is not mutated, and no warning fires when the option is absent. The babel-preset-env normalize-options suite passes (30 tests) and make tscheck is clean across the monorepo.

Closes #18096

AI was used for assistance.