K1NG-Driver/includes/tomlc17-R260618/BAREKEYCHAR.md

Bare Key Characters in TOML v1.1

In TOML v1.1, the definition of a bare key (unquoted key) has been significantly expanded from the strict ASCII-only restriction of TOML v1.0 to support internationalization.

1. The TOML v1.0 Definition (Legacy)

In TOML v1.0, a bare key could only contain:

• ASCII letters (A-Z, a-z)
• ASCII digits (0-9)
• Underscores (_)
• Dashes (-)

2. The TOML v1.1 Expansion

TOML v1.1 allows non-ASCII Unicode characters in bare keys. The character ranges are largely aligned with the XML 1.1 NameChar specification, which covers most letters, digits, and combining marks from scripts worldwide.

A bare-key-char in TOML v1.1 is defined as:

• Any character allowed in v1.0 ([A-Za-z0-9_-]).
• Any non-ASCII Unicode codepoint from the following specific ranges:
  • U+00B2, U+00B3, U+00B9 (Superscripts)
  • U+00BC to U+00BE (Fractions)
  • U+00C0 to U+00D6
  • U+00D8 to U+00F6
  • U+00F8 to U+037D
  • U+037F to U+1FFF
  • U+200C to U+200D (Zero-width joiners)
  • U+203F to U+2040
  • U+2070 to U+218F
  • U+2460 to U+24FF
  • U+2C00 to U+2FEF
  • U+3001 to U+D7FF
  • U+F900 to U+FDCF
  • U+FDF0 to U+FFFD
  • U+10000 to U+EFFFF (Supplementary Planes)

Summary Table

Feature	TOML v1.0	TOML v1.1
Allowed Characters	[A-Za-z0-9_-]	[A-Za-z0-9_-] + Wide Unicode ranges
Examples	key = "val"	café = "coffee", ñoño = "val", 日本語 = "val"
Prohibited	café = "val" (must use "café")	Whitespace, ., [, ], #, =, etc.

Implementation Status in tomlc17

The tomlc17 project recently updated its scanner in commit df7ecd4 to support these TOML v1.1 ranges using a new helper function is_unicode_bare_key_char(). This allows the parser to correctly handle unquoted internationalized keys.