just/grammar.md

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justfile grammar
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================
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Justfiles are processed with a mildly context-sensitive tokenizer
and a recursive descent parser. The grammar is mostly LL(1),
although an extra token of lookahead is used to distinguish between
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export assignments and recipes with arguments.
tokens
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------
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```
BACKTICK = `[^`\n\r]*`
COLON = :
COMMENT = #([^!].*)?$
EOL = \n|\r\n
EQUALS = =
INTERPOLATION_START = {{
INTERPOLATION_END = }}
NAME = [a-zA-Z_-][a-zA-Z0-9_-]*
PLUS = +
RAW_STRING = '[^'\r\n]*'
STRING = "[^"]*" # also processes \n \r \t \" \\ escapes
INDENT = emitted when indentation increases
DEDENT = emitted when indentation decreases
LINE = emitted before a recipe line
TEXT = recipe text, only matches in a recipe body
```
grammar
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-------
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```
justfile : item* EOF
item : recipe
| assignment
| export
| EOL
assignment : NAME EQUALS expression EOL
export : 'export' assignment
expression : STRING
| RAW_STRING
| NAME
| expression '+' expression
recipe : NAME arguments? ':' dependencies? body?
arguments : NAME+
dependencies : NAME+
body : INDENT line+ DEDENT
line : LINE (TEXT | interpolation)+ EOL
interpolation : '{{' expression '}}'
```