TypeError: WebAssembly.instantiate(): Imports argument must be present and must be an object

[UebelAndre]

Describe the Bug

I was working on bazelbuild/rules_rust#3174 and noticed when I bumped wasm-bindgen from 0.2.93 to 0.2.95 I started seeing:

[TypeError: WebAssembly.instantiate(): Imports argument must be present and must be an object]

I know Bazel is not a consideration for this repo but I'm still hoping someone could shed some light on why I might be seeing this issue on 0.2.95. I'm currently trying to bump to 0.2.99 and see the same failure there.

I've tried using the following diff and all it did was change the error slightly

diff --git a/extensions/wasm_bindgen/rules_js/test/hello_world_wasm_test.js b/extensions/wasm_bindgen/rules_js/test/hello_world_wasm_test.js
index 61fc3839..f8dbfdbb 100644
--- a/extensions/wasm_bindgen/rules_js/test/hello_world_wasm_test.js
+++ b/extensions/wasm_bindgen/rules_js/test/hello_world_wasm_test.js
@@ -15,7 +15,7 @@ const main = async function (typ, dir) {
     const buf = fs.readFileSync(wasm_file);
     assert.ok(buf);

-    const res = await WebAssembly.instantiate(buf);
+    const res = await WebAssembly.instantiate(buf, {});
     assert.ok(res);
     assert.strictEqual(res.instance.exports.double(2), 4);
 };

[TypeError: WebAssembly.instantiate(): Import #0 module="wbg" error: module is not an object or function]

A clear and concise description of what the bug is.

Steps to Reproduce

I do not have a repro outside of Bazel but with bazelbuild/rules_rust#3174 the error can be reproduced:

• navigate to extensions/wasm_bindgen
• run bazel test //...

Expected Behavior

There should be no error caused by the test.

Actual Behavior

The test should pass as it used to on 0.2.93.

[daxpedda]

I'm assuming this is again related to #4133. It could be that your tests didn't require any imports, but they do now with reference types enabled by default. Specifically __wbindgen_init_externref_table is needed, as you can see in the diff of #4253.

[UebelAndre]

Thanks for the info!

What can I do to confirm that a new import is being used/is needed and how could I update my test to provide this import? The test currently looks like

"use strict";
const fs = require("fs");
const path = require("path");
const assert = require("assert");

const main = async function (typ, dir) {
    const wasm_file = path.join(
        __dirname,
        "..",
        dir,
        "test",
        "hello_world_" + typ + "_wasm_bindgen",
        "hello_world_" + typ + "_wasm_bindgen_bg.wasm",
    );
    const buf = fs.readFileSync(wasm_file);
    assert.ok(buf);

    const res = await WebAssembly.instantiate(buf);
    assert.ok(res);
    assert.strictEqual(res.instance.exports.double(2), 4);
};

["bundler", "web", "deno", "nomodules", "nodejs"].forEach((typ) => {
    main(typ, process.argv.length > 2 ? process.argv[2] : "").catch(function (
        err,
    ) {
        console.error(err);
        process.exit(1);
    });
});

[daxpedda]

The way wasm-bindgen works is that it generates a JS shim to provide these imports. You have to import that shim and either let it do the instantiation, the supported way to do this, or emulate it in some way. Either way, I recommend you take a look at the shim.