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Jarred Sumner e8b2455f11 feat: add Bun.JSONL.parse() for streaming newline-delimited JSON parsing (#26356 )

Adds a built-in JSONL parser implemented in C++ using JavaScriptCore's
optimized JSON parser.

## API

### `Bun.JSONL.parse(input)`
Parse a complete JSONL string or `Uint8Array` and return an array of all
parsed values. Throws on invalid input.

```ts
const results = Bun.JSONL.parse('{"a":1}\n{"b":2}\n');
// [{ a: 1 }, { b: 2 }]
```

### `Bun.JSONL.parseChunk(input, start?, end?)`
Parse as many complete values as possible, returning `{ values, read,
done, error }`. Designed for streaming use cases where input arrives
incrementally.

```ts
const result = Bun.JSONL.parseChunk('{"id":1}\n{"id":2}\n{"id":3');
result.values; // [{ id: 1 }, { id: 2 }]
result.read;   // 17
result.done;   // false
result.error;  // null
```

## Implementation Details

- C++ implementation in `BunObject.cpp` using JSC's `streamingJSONParse`
- ASCII fast path: zero-copy `StringView` for pure ASCII input
- Non-ASCII: uses `fromUTF8ReplacingInvalidSequences` with
`utf16_length_from_utf8` size check to prevent overflow
- UTF-8 BOM automatically skipped for `Uint8Array` input
- Pre-built `Structure` with fixed property offsets for fast result
object creation
- `Symbol.toStringTag = "JSONL"` on the namespace object
- `parseChunk` returns errors in `error` property instead of throwing,
preserving partial results
- Comprehensive boundary checks on start/end parameters

## Tests

234 tests covering:
- Complete and partial/streaming input scenarios
- Error handling and recovery
- UTF-8 multi-byte characters and BOM handling
- start/end boundary security (exhaustive combinations, clamping, OOB
prevention)
- 4 GB input rejection (both ASCII and non-ASCII paths)
- Edge cases (empty input, single values, whitespace, special numbers)

---------

Co-authored-by: Claude <noreply@anthropic.com>
Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>

2026-01-23 00:23:25 -08:00