Add a fallback for argumentsLength without mutable-globals

Author: dcodeIO

cli/asc.json

@@ -210,15 +210,16 @@
       " exception-handling  Exception handling.",
       " tail-calls          Tail call operations."
     ],
-    "type": "s"
+    "type": "S"
   },
   "disable": {
     "description": [
       "Disables WebAssembly features that are enabled by default.",
       "",
       " mutable-globals     Mutable global imports and exports.",
       ""
-    ]
+    ],
+    "type": "S"
   },
   "transform": {
     "description": "Specifies the path to a custom transform to 'require'.",

lib/loader/index.js

@@ -277,9 +277,9 @@ function postInstantiate(baseModule, instance) {
 }
 
 /** Wraps a WebAssembly function while also taking care of variable arguments. */
-function wrapFunction(fn, argumentsLength) {
+function wrapFunction(fn, setArgumentsLength) {
   var wrap = (...args) => {
-    if (argumentsLength) argumentsLength.value = args.length;
+    setArgumentsLength(args.length);
     return fn(...args);
   }
   wrap.original = fn;
@@ -342,7 +342,10 @@ exports.instantiateStreaming = instantiateStreaming;
 /** Demangles an AssemblyScript module's exports to a friendly object structure. */
 function demangle(exports, baseModule) {
   var module = baseModule ? Object.create(baseModule) : {};
-  var argumentsLength = exports["__argumentsLength"];
+  function setArgumentsLength(length) {
+    if (exports["__argumentsLength"]) exports["__argumentsLength"].value = length;
+    else if (exports["set:__argumentsLength"]) exports["set:__argumentsLength"](length);
+  }
   function hasOwnProperty(elem, prop) {
     return Object.prototype.hasOwnProperty.call(elem, prop);
   }
@@ -392,11 +395,11 @@ function demangle(exports, baseModule) {
         }
       } else {
         if (name === 'constructor') {
-          curr[name] = wrapFunction(elem, argumentsLength);
+          curr[name] = wrapFunction(elem, setArgumentsLength);
         } else { // for methods
           Object.defineProperty(curr, name, {
             value: function (...args) {
-              if (argumentsLength) argumentsLength.value = args.length;
+              setArgumentsLength(args.length);
               return elem(this[THIS], ...args);
             }
           });
@@ -412,7 +415,7 @@ function demangle(exports, baseModule) {
           });
         }
       } else if (typeof elem === "function") {
-        curr[name] = wrapFunction(elem, argumentsLength);
+        curr[name] = wrapFunction(elem, setArgumentsLength);
       } else {
         curr[name] = elem;
       }

lib/loader/package.json

@@ -24,7 +24,9 @@
   "main": "index.js",
   "types": "index.d.ts",
   "scripts": {
-    "test:build": "asc tests/assembly/index.ts -b tests/build/untouched.wasm",
+    "asbuild": "npm run asbuild:default && npm run asbuild:legacy",
+    "asbuild:default": "asc tests/assembly/index.ts -b tests/build/default.wasm",
+    "asbuild:legacy": "asc tests/assembly/index.ts --disable mutable-globals -b tests/build/legacy.wasm",
     "test": "node tests"
   },
   "files": [