kdl/CHANGELOG.md

KDL Changelog

2.0.0 (2024-02-07)

Grammar

• Solidus/Forward slash (/) is no longer an escaped character.
• Space (U+0020) can now be written into quoted strings with the \s escape.
• Single line comments (//) can now be immediately followed by a newline.
• All literal whitespace following a \ in a string is now discarded.
• Vertical tabs (U+000B) are now considered to be whitespace.
• The grammar syntax itself has been described, and some confusing definitions in the grammar have been fixed accordingly (mostly related to escaped characters).
• ,, <, and > are now legal identifier characters. They were previously reserved for KQL but this is no longer necessary.
• Code points under 0x20, code points above 0x10FFFF, Delete control character (0x7F), and the unicode "direction control" characters are now completely banned from appearing literally in KDL documents. They can now only be represented in regular strings, and there's no facilities to represent them in raw strings. This should be considered a security improvement.
• Raw strings no longer require an r prefix: they are now specified by using #""#.
• Line continuations can be followed by an EOF now, instead of requiring a newline (or comment). node \<EOF> is now a legal KDL document.
• # is no longer a legal identifier character.
• null, true, and false are now #null, #true, and #false. Using the unprefixed versions of these values is a syntax error.
• The spec prose has more explicitly stated that whitespace and newlines are not valid identifier characters, even though the grammar already expressed this.
• Bare identifiers can now be used as values in Arguments and Properties, and are interpreted as string values.
• The spec prose now more explicitly states that strings and raw strings can be used as type annotations.
• A statement in the spec prose that said "It is reasonable for an implementation to ignore null values altogether when deserializing". This is no longer encouraged or desired.
• Code points have been constrained to Unicode Scalar Values only, including values used in string escapes (\u{}). All KDL documents and string values should be valid UTF-8 now, as was intended.
• The last node in a child block no longer needs to be terminated with ;, even if the closing } is on the same line, so this is now a legal node: node {foo;bar;baz}
• More places allow whitespace (node-spaces, specifically) now. With great power comes great responsibility:
  • Inside (foo) annotations (so, ( foo ) would be legal (( f oo ) would not be, since it has two identifiers))
  • Between annotations and the thing they're annotating ((blah) node (thing) 1 y= (who) 2)
  • Around = for props (x = 1)
• The BOM is now only allowed as the first character in a document. It was previously treated as generic whitespace.
• Multi-line strings are now automatically dedented, according to the common whitespace matching the whitespace prefix of the closing line. Multiline strings and raw strings now must have a newline immediately following their opening ", and a final newline plus whitespace preceding the closing ".
• SMALL EQUALS SIGN (U+FE66), FULLWIDTH EQUALS SIGN (U+FF1D), and HEAVY EQUALS SIGN (U+1F7F0) are now treated the same as = and can be used for properties (e.g. お名前＝☜(ﾟヮﾟ☜)). They are also no longer valid in bare identifiers.
• .1, +.1 etc are no longer valid identifiers, to prevent confusion and conflicts with numbers.

KQL

• There's now a required descendant selector (>>), instead of using plain spaces for that purpose.
• The "any sibling" selector is now ++ instead of ~, for consistency with the new descendant selector.
• Map operators have been removed entirely.