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 `==`.
98 lines
2.1 KiB
Markdown
98 lines
2.1 KiB
Markdown
justfile grammar
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================
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Justfiles are processed by a mildly context-sensitive tokenizer
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and a recursive descent parser. The grammar is LL(k), for an
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unknown but hopefully reasonable value of k.
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tokens
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------
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```
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BACKTICK = `[^`\n\r]*`
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COMMENT = #([^!].*)?$
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DEDENT = emitted when indentation decreases
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EOF = emitted at the end of the file
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INDENT = emitted when indentation increases
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LINE = emitted before a recipe line
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NAME = [a-zA-Z_][a-zA-Z0-9_-]*
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NEWLINE = \n|\r\n
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RAW_STRING = '[^'\r\n]*'
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STRING = "[^"]*" # also processes \n \r \t \" \\ escapes
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TEXT = recipe text, only matches in a recipe body
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```
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grammar syntax
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--------------
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```
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| alternation
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() grouping
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_? option (0 or 1 times)
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_* repetition (0 or more times)
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_+ repetition (1 or more times)
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```
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grammar
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-------
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```
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justfile : item* EOF
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item : recipe
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| alias
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| assignment
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| export
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| setting
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| eol
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eol : NEWLINE
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| COMMENT NEWLINE
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alias : 'alias' NAME ':=' NAME
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assignment : NAME ':=' expression eol
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export : 'export' assignment
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setting : 'set' 'shell' ':=' '[' string (',' string)* ','? ']'
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expression : 'if' condition '{' expression '}' else '{' expression '}'
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| value '+' expression
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| value
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condition : expression '==' expression
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| expression '!=' expression
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value : NAME '(' sequence? ')'
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| STRING
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| RAW_STRING
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| BACKTICK
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| NAME
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| '(' expression ')'
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string : STRING
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| RAW_STRING
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sequence : expression ',' sequence
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| expression ','?
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recipe : '@'? NAME parameter* variadic? ':' dependency* body?
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parameter : NAME
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| NAME '=' value
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variadic : '*' parameter
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| '+' parameter
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dependency : NAME
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| '(' NAME expression* ')
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body : INDENT line+ DEDENT
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line : LINE (TEXT | interpolation)+ NEWLINE
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| NEWLINE
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interpolation : '{{' expression '}}'
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```
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