fix: use temporal-polyfill via npm overrides to resolve JSBI issues

[KristjanESPERANTO]

Fixes #441

Problem

Users cannot upgrade from v0.22.1 to v0.23+ when using Next.js with Turbopack due to bundler errors:

Error: e.BigInt is not a function

The issue occurs because rrule-temporal depends on @js-temporal/polyfill, which uses the JSBI library to polyfill BigInt. Modern bundlers like Turbopack and Webpack fail to properly tree-shake or optimize JSBI's emulation code.

Solution

This PR uses npm overrides to replace @js-temporal/polyfill with temporal-polyfill, which uses native BigInt instead of JSBI. Both polyfills implement the same Temporal API and are compatible via duck-typing.

Changes:

• Added npm override in package.json to redirect @js-temporal/polyfill to temporal-polyfill@^0.3.0
• Added tests to verify JSBI is removed and correct polyfill is loaded

Why npm overrides?

This isn't the ideal solution, but it seems the most pragmatic approach because:

1. The rrule-temporal maintainer does not intend to switch to temporal-polyfill (see rrule-temporal/issue #94).
2. @js-temporal/polyfill PR #167, which would allow users to choose between JSBI and native BigInt, has not been merged and is stalled for a long time.
3. Once Node.js ships native Temporal support, all polyfills become obsolete anyway

Impact

• Works with Next.js Turbopack and Webpack
• Smaller bundle size
• Native BigInt operations instead of JSBI emulation
• Better tree-shaking in modern bundlers

Summary by CodeRabbit

• Chores

  • Updated Temporal polyfill dependency to use an alternative package implementation.

• Tests

  • Added test suite to verify Temporal polyfill dependency resolution and module loading behavior.

[coderabbitai]

📝 Walkthrough

Walkthrough

This pull request switches the temporal polyfill from @js-temporal/polyfill to npm:temporal-polyfill@^0.3.0 using npm overrides, and adds tests to verify correct polyfill resolution. A lint rule is disabled to accommodate the dependency configuration.

Changes

Cohort / File(s)	Summary
Dependency Configuration package.json	Removed direct @js-temporal/polyfill dependency; added npm overrides to map it to temporal-polyfill@^0.3.0. Added import-x/no-extraneous-dependencies lint rule disable.
Polyfill Verification Tests test/polyfill-check.test.js	New test suite verifying JSBI is not installed, @js-temporal/polyfill resolves to temporal-polyfill, and runtime module loading confirms correct package name.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~12 minutes

Poem

🐰 A BigInt bug brought tears to the day,
But a polyfill swap saved the way!
Temporal flows through temporal-polyfill's embrace,
Tests now ensure we're in the right place. ✨

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately describes the main change: replacing @js-temporal/polyfill with temporal-polyfill via npm overrides to fix JSBI-related issues.
Linked Issues check	✅ Passed	The PR directly addresses issue #441 by implementing a solution to replace the JSBI-based @js-temporal/polyfill with temporal-polyfill, which resolves the 'e.BigInt is not a function' error in Next.js with Turbopack.
Out of Scope Changes check	✅ Passed	All changes are scoped to resolving the JSBI issue: package.json dependency override, lint rule addition, and verification tests. No unrelated changes detected.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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✨ Finishing touches

• 📝 Generate docstrings

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment

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