kdl/CHANGELOG.md

KDL Changelog

2.0.0 (2022-08-28)

Grammar

• Solidus/Forward slash (/) is no longer an escaped character.
• 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.
• Identifiers can't start with r#, so they're easy to distinguish from raw strings. (They already similarly can't start with a digit, or a sign+digit, so they're easy to distinguish from numbers.)
• 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.

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.