## Summary
Fixes `Buffer.isEncoding('')` to return `false` instead of `true`,
matching Node.js behavior.
## Description
Previously, `Buffer.isEncoding('')` incorrectly returned `true` in Bun,
while Node.js correctly returns `false`. This was caused by
`parseEnumerationFromView` in `JSBufferEncodingType.cpp` treating empty
strings (length 0) as valid utf8 encoding.
The fix modifies the switch statement to return `std::nullopt` for empty
strings, along with other invalid short strings.
## Changes
- Modified `src/bun.js/bindings/JSBufferEncodingType.cpp` to return
`std::nullopt` for empty strings
- Added regression test `test/regression/issue23966.test.ts`
## Test Plan
- [x] Test fails with `USE_SYSTEM_BUN=1 bun test
test/regression/issue23966.test.ts` (confirms bug exists)
- [x] Test passes with `bun bd test test/regression/issue23966.test.ts`
(confirms fix works)
- [x] Verified behavior matches Node.js v24.3.0
- [x] All test cases for valid/invalid encodings pass
Fixes#23966🤖 Generated with [Claude Code](https://claude.com/claude-code)
---------
Co-authored-by: Claude Bot <claude-bot@bun.sh>
Co-authored-by: Claude <noreply@anthropic.com>
