Wasm: dispatch lifecycle events when async instantiation completes

CHANGES.md

@@ -3,6 +3,9 @@
 ## Features/Changes
 * Lib: fix the type of some DOM properties and methods (#1747)
 * Test: use dune test stanzas (#1631)
+* Wasm: dispatch `wasmoocaml:loaded` and `wasmoocaml:error` `CustomEvent`s on
+  `globalThis` so that surrounding JavaScript can wait for the asynchronous
+  Wasm instantiation to complete (#11)
 
 # 5.9.1 (02-12-2024) - Lille
 

runtime/wasm/runtime.js

@@ -531,35 +531,50 @@
     }
     return { instance: { exports: Object.assign(imports.env, imports.OCaml) } };
   }
-  const wasmModule = await instantiateFromDir();
+  function dispatchLifecycleEvent(name, detail) {
+    if (
+      typeof globalThis.dispatchEvent === "function" &&
+      typeof CustomEvent === "function"
+    ) {
+      globalThis.dispatchEvent(new CustomEvent(name, { detail }));
+    }
+  }
+
+  try {
+    const wasmModule = await instantiateFromDir();
 
-  var {
-    caml_callback,
-    caml_alloc_tm,
-    caml_start_fiber,
-    caml_handle_uncaught_exception,
-    caml_buffer,
-    caml_extract_string,
-    string_get,
-    string_set,
-    _initialize,
-  } = wasmModule.instance.exports;
+    var {
+      caml_callback,
+      caml_alloc_tm,
+      caml_start_fiber,
+      caml_handle_uncaught_exception,
+      caml_buffer,
+      caml_extract_string,
+      string_get,
+      string_set,
+      _initialize,
+    } = wasmModule.instance.exports;
 
-  var buffer = caml_buffer?.buffer;
-  var out_buffer = buffer && new Uint8Array(buffer, 0, buffer.length);
+    var buffer = caml_buffer?.buffer;
+    var out_buffer = buffer && new Uint8Array(buffer, 0, buffer.length);
 
-  start_fiber = make_promising(caml_start_fiber);
-  var _initialize = make_promising(_initialize);
-  var process = globalThis.process;
-  if (process && process.on) {
-    process.on("uncaughtException", (err, origin) =>
-      caml_handle_uncaught_exception(err),
-    );
-  } else if (globalThis.addEventListener) {
-    globalThis.addEventListener(
-      "error",
-      (event) => event.error && caml_handle_uncaught_exception(event.error),
-    );
+    start_fiber = make_promising(caml_start_fiber);
+    var _initialize = make_promising(_initialize);
+    var process = globalThis.process;
+    if (process && process.on) {
+      process.on("uncaughtException", (err, origin) =>
+        caml_handle_uncaught_exception(err),
+      );
+    } else if (globalThis.addEventListener) {
+      globalThis.addEventListener(
+        "error",
+        (event) => event.error && caml_handle_uncaught_exception(event.error),
+      );
+    }
+    await _initialize();
+    dispatchLifecycleEvent("wasmoocaml:loaded", { src });
+  } catch (error) {
+    dispatchLifecycleEvent("wasmoocaml:error", { src, error });
+    throw error;
   }
-  await _initialize();
 };