rontolisp.wasm/export

(export var options) with [rontolisp.wasm :as wasm], or {:wasm/export options} in a defn's attr map (or its name's metadata)

Exports the function var names, so the host can call it (WASM host functions). The options map:

• :as -- the name the host calls it by; the var's name by default.
• :params -- a vector of type keywords, one per argument; none by default.
• :returns -- the result's type keyword; :void by default (the result is dropped).

The var resolves where the declaration stands, after the whole file has lowered: it may be defined below, and a redefined defn exports its newest definition. A single-arity defn taking exactly the declared parameters is exported as itself, the way a hand-written rontolisp:wasm-export names a defun. Anything else is exported through a function of the declared arity that calls the var: a defn with several arities or a rest parameter, a def'd function, a multimethod. A defn with no arity taking that many arguments is refused, naming the export. The metadata stays on the var as written.

$ cat calc.clj
(ns calc (:require [rontolisp.wasm :as wasm]))

(defn positive? {:wasm/export {:as "is-positive" :params [:s32] :returns :bool}} [n]
  (> n 0))

(defn total ([a] a) ([a b] (+ a b)))
(wasm/export total {:params [:s32 :s32] :returns :s32})
$ rontolisp calc.clj -o calc.wasm --component
$ wasmtime run --invoke 'is-positive(-3)' calc.wasm
false
$ wasmtime run --invoke 'total(2, 40)' calc.wasm
42

A program implementing a WIT world declares its exports with rontolisp.wit/export instead; the two are not combined. On the interpreter and the JVM nothing is exported and the function stays an ordinary one.