fix: support UTF-16 surrogate pairs in unicode escape sequences #59
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Implements RFC 8259 § 7 compliant handling of UTF-16 surrogate pairs. Non-BMP characters (U+10000 to U+10FFFF) encoded as surrogate pairs like \uD834\uDD1E are now correctly decoded to their Unicode code points. The parser now: - Detects high surrogates (0xD800-0xDBFF) and looks ahead for low surrogates - Combines pairs using the formula: ((high - 0xD800) * 0x400) + (low - 0xDC00) + 0x10000 - Validates all edge cases with descriptive error messages - Maintains backward compatibility for normal \uXXXX escapes Added comprehensive tests covering valid pairs, multiple pairs, mixed content, and all error cases for unpaired surrogates.
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Pull Request Overview
This PR implements RFC 8259 § 7 compliant UTF-16 surrogate pair handling, enabling the parser to correctly decode non-BMP Unicode characters (U+10000 to U+10FFFF) that are encoded as surrogate pairs in JSON escape sequences.
- Adds detection and combination logic for UTF-16 surrogate pairs (high: 0xD800-0xDBFF, low: 0xDC00-0xDFFF)
- Implements validation for all edge cases with descriptive error messages for unpaired surrogates
- Maintains backward compatibility for standard \uXXXX Unicode escapes
Reviewed Changes
Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.
| File | Description |
|---|---|
| src/string.rs | Core implementation of surrogate pair detection, validation, and decoding using the RFC 8259 formula |
| src/scanner.rs | Updated error message for unpaired low surrogate to reflect new validation |
| src/parse_to_value.rs | Comprehensive test suite covering valid pairs, multiple pairs, mixed content, and error cases |
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This was referenced Nov 12, 2025
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Implements RFC 8259 § 7 compliant handling of UTF-16 surrogate pairs. Non-BMP characters (U+10000 to U+10FFFF) encoded as surrogate pairs like \uD834\uDD1E are now correctly decoded to their Unicode code points.
The parser now:
Added comprehensive tests covering valid pairs, multiple pairs, mixed content, and all error cases for unpaired surrogates.
fixes #31