utilities/just
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just/GRAMMAR.md
Casey Rodarmor cef117f8bd Report line number in recipe failure messages (#125) 
The grammar now permits blank lines in recipes.

Note that inside of recipes, the token `NEWLINE` is used instead of the
non-terminal `eol`. This is because an `eol` optionally includes a
comment, whereas inside recipes bodies comments get no special
treatment.
2016-11-16 22:18:55 -08:00

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justfile grammar

Justfiles are processed by 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 export assignments and recipes with arguments.

tokens

BACKTICK            = `[^`\n\r]*`
COLON               = :
COMMENT             = #([^!].*)?$
NEWLINE             = \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

justfile      : item* EOF

item          : recipe
              | assignment
              | export
              | eol

eol           : NEWLINE
              | COMMENT NEWLINE

assignment    : NAME '=' expression eol

export        : 'export' assignment

expression    : STRING
              | RAW_STRING
              | NAME
              | BACKTICK
              | expression '+' expression

recipe        : '@'? NAME argument* ':' dependencies? body?

argument      : NAME
              | NAME '=' STRING
              | NAME '=' RAW_STRING

dependencies  : NAME+

body          : INDENT line+ DEDENT

line          : LINE (TEXT | interpolation)+ NEWLINE
              | NEWLINE

interpolation : '{{' expression '}}'