mirror of https://github.com/kdl-org/kdl.git
150 lines
3.8 KiB
Markdown
150 lines
3.8 KiB
Markdown
# kdl - Kat's Document Language
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kdl is a document language, mostly based on [SDLang](https://sdlang.org), with
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xml-like semantics that looks like you're invoking a bunch of CLI commands!
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It's meant to be used both as a serialization format and a configuration
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language, and is relatively light on syntax compared to XML.
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## Intro
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The basic syntax is similar to SDLang:
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```kdl
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// This is a node with a single string value
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title "Hello, World"
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// Multiple values are supported, too
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bookmarks 12 15 188 1234
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// Nodes can have attributes
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author "Alex Monad" email="alex@example.com" active=true
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// Nodes can be arbitrarily nested
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contents {
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section "First section" {
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paragraph "This is the first paragraph"
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paragraph "This is the second paragraph"
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}
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}
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// Nodes can be separated into multiple lines
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title \
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"Some title"
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// Comment formats:
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// C++ style
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/*
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C style multiline
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*/
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tag /*foo=true*/ bar=false
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```
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But kdl changes a few details:
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```kdl
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// Files must be utf8 encoded!
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smile "😁"
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// Instead of anonymous nodes, nodes and properties can be wrapped
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// in "" for arbitrary node names.
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"!@#$@$%Q#$%~@!40" "1.2.3" "!!!!!"=true
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// The following is a legal bare identifier:
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foo123~!@#$%^&*.:'|<>/?+ "weeee"
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// kdl specifically allows properties and values to be
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// interspersed with each other, much like CLI commands.
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foo bar=true "baz" quux=false 1 2 3
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// strings can be multiline as-is, without a different syntax.
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string "my
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multiline
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value"
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// raw/unescaped strings use the "r" prefix on string literals and
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// otherwise behave the same, including multiline support.
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raw r"C:\Users\kdl"
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// You can add any number of # after the r and the last " to
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// disambiguate literal " characters.
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other-raw r#"hello"world"#
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// There is a single decimal number type, much like JSON's.
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num 1.234e-42
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// Numbers can have underscores to help readability:
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bignum 1_000_000
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// There is additional support for literal hexadecimal, octal, and binary input.
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my-hex 0xdeadbeef
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my-octal 0o755
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my-binary 0b1010_1101
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```
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The following SDLang features are removed altogether:
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* "Anonymous" nodes
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* Binary data literals
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* Date/time formats
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* `on` and `off` booleans
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* Backtick strings
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* Semicolons
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* Namespaces with `:`
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* Shell style (`#`) and Lua-style (`--`) comments
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* Distinction between 32/64/128-bit numbers. There's just numbers.
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## Design and Discussion
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kdl is still extremely new, and discussion about the format should happen over
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on the [discussions page](https://github.com/zkat/kdl/discussions). Feel free
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to jump in and give us your 2 cents!
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## Grammar
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```
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nodes := linespace* (node (newline nodes)? linespace*)?
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node := identifier (node-space node-argument)* (node-space node-document)? single-line-comment?
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node-argument := prop | value
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node-children := '{' nodes '}'
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node-space := ws* escline ws* | ws+
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identifier := [a-zA-Z] [a-zA-Z0-9!#$%&'*+\-./:<>?@\^_|~]* | string
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prop := identifier '=' value
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value := string | raw_string | number | boolean | 'null'
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string := '"' ('\\' ["\\] | [^"])* '"'
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raw-string := 'r' raw-string-hash
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raw-string-hash := '#' raw-string-hash '#' | raw-string-quotes
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raw-string-quotes := '"' .* '"'
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number := decimal | hex | octal | binary
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decimal := integer ('.' [0-9]+)? exponent?
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exponent := ('e' | 'E') integer
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integer := sign? [0-9] [0-9_]*
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sign := '+' | '-'
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hex := '0x' [0-9a-fA-F] [0-9a-fA-F_]*
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octal := '0o' [0-7] [0-7_]*
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binary := '0b' ('0' | '1') ('0' | '1' | '_')*
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boolean := 'true' | 'false'
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escline := '\\' ws* (single-line-comment | newline)
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linespace := newline | ws | single-line-comment
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newline := ('\r' '\n') | '\n'
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ws := bom | ' ' | '\t' | multi-line-comment
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single-line-comment := '//' ('\r' [^\n] | [^\r\n])* newline
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multi-line-comment := '/*' ('*' [^\/] | [^*])* '*/'
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```
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