`swc-plugin` for Next.js Error Code Transformation

Overview

This plugin transforms Next.js source code by:

Rewriting new Error or Error to include an additional property: Object.defineProperty(new Error(...), "__NEXT_ERROR_CODE", { value: $code, enumerable: false, configurable: true }). The enumerable: false ensures the error code won't show up in console logs while still being accessible for telemetry. The configurable: true ensures the error code can be overwritten, useful for transforming errors.
This enables anonymous error code reporting for user feedback while keeping the message private.

File Location: packages/next/errors.json
Structure: Append-only, increment-based mapping of error codes to messages.
Automation:
- Running pnpm build automatically updates errors.json if new errors are introduced.
- Commit Reminder: Always commit the updated errors.json file to avoid CI failures.

Two-Pass Build:
1. First Pass:
  - Extracts new errors and temporarily stores them in packages/next/.errors/*.json.
  - In CI, a build with new errors will fail.
2. Second Pass:
  - Updates packages/next/errors.json and reruns the build step to confirm no further new errors.
  - Inspired by React's error mapping mechanism.
Concurrency Handling: The two-pass system ensures reliable ordering of inserted error codes during concurrent builds.

WASM Rebuild Required:
- After modifying the plugin, rebuild the WASM file via pnpm build-error-code-plugin and commit it to the repository.
- Reason: Pre-built artifacts simplify the build process (pnpm build runs without requiring cargo).
Testing: Run cargo test inside the crates/next-error-code-swc-plugin directory to test the plugin.