compile/define-fence

Syntax: (define-fence NAME [RAW META] BODY ...)

Behaviour: Defines a fence handler. NAME is the binding the fence dispatch looks up, normally fence/<format>; RAW and META name the handler’s two parameters. The macro expands to a var of NAME bound to a FenceHandler wrapping the body as a demanding function, so the handler runs at compile time.

RAW is the fence body text, verbatim. META is a dict carrying name, filename, line, col, and options, where options is the opener-line keyword plist as a dict. The body returns Koskari source, which is compiled in place of the fence – usually a quasiquoted template.

A handler validates its own options and raises FenceError for ones it does not accept. Handlers must not suspend.

Examples:

>>> define-fence fence/shout [raw meta]:
...   `(.upper ,(raw.strip))

Used as a triple-backtick fence:

var loud ```shout
hello there
```

>>> loud
"HELLO THERE"

A handler that rejects unknown options and builds a list:

>>> define-fence fence/lines [raw meta]:
...   var options (meta.get "options")
...   when options:
...     raise (FenceError f"fence/lines got unknown options: {(sorted options)}")
...   `(#list ,@(map str (.splitlines (raw.strip))))

var ls ```lines
a
b
```

>>> ls
#["a" "b"]

See also: Fence handlers, compile/apply-fence, Fences.