19f7ad09a7
Add conditional expressions of the form:
foo := if lhs == rhs { then } else { otherwise }
`lhs`, `rhs`, `then`, and `otherwise` are all arbitrary expressions, and
can recursively include other conditionals. Conditionals short-circuit,
so the branch not taken isn't evaluated.
It is also possible to test for inequality with `==`.
2.1 KiB
2.1 KiB
justfile grammar
Justfiles are processed by a mildly context-sensitive tokenizer and a recursive descent parser. The grammar is LL(k), for an unknown but hopefully reasonable value of k.
tokens
BACKTICK = `[^`\n\r]*`
COMMENT = #([^!].*)?$
DEDENT = emitted when indentation decreases
EOF = emitted at the end of the file
INDENT = emitted when indentation increases
LINE = emitted before a recipe line
NAME = [a-zA-Z_][a-zA-Z0-9_-]*
NEWLINE = \n|\r\n
RAW_STRING = '[^'\r\n]*'
STRING = "[^"]*" # also processes \n \r \t \" \\ escapes
TEXT = recipe text, only matches in a recipe body
grammar syntax
| alternation
() grouping
_? option (0 or 1 times)
_* repetition (0 or more times)
_+ repetition (1 or more times)
grammar
justfile : item* EOF
item : recipe
| alias
| assignment
| export
| setting
| eol
eol : NEWLINE
| COMMENT NEWLINE
alias : 'alias' NAME ':=' NAME
assignment : NAME ':=' expression eol
export : 'export' assignment
setting : 'set' 'shell' ':=' '[' string (',' string)* ','? ']'
expression : 'if' condition '{' expression '}' else '{' expression '}'
| value '+' expression
| value
condition : expression '==' expression
| expression '!=' expression
value : NAME '(' sequence? ')'
| STRING
| RAW_STRING
| BACKTICK
| NAME
| '(' expression ')'
string : STRING
| RAW_STRING
sequence : expression ',' sequence
| expression ','?
recipe : '@'? NAME parameter* variadic? ':' dependency* body?
parameter : NAME
| NAME '=' value
variadic : '*' parameter
| '+' parameter
dependency : NAME
| '(' NAME expression* ')
body : INDENT line+ DEDENT
line : LINE (TEXT | interpolation)+ NEWLINE
| NEWLINE
interpolation : '{{' expression '}}'