wasm: Fix Webpack compatibility for browser use

Updating emsdk to v3.1.27 was necessary for emscripten-core/emscripten#17915,
which allows using the same WASM build for both browser and nodejs envs.

Author: shesek

contrib/bullseye_deps.sh

@@ -22,8 +22,8 @@ unzip -qq ${NDK_FILENAME}
 rm ${NDK_FILENAME}
 git clone https://github.com/emscripten-core/emsdk
 cd emsdk
-./emsdk install 3.1.20
-./emsdk activate 3.1.20
+./emsdk install 3.1.27
+./emsdk activate 3.1.27
 source ./emsdk_env.sh
 
 apt-get remove --purge curl unzip -yqq

src/wasm_package/.gitignore

@@ -1 +1,2 @@
 libwally_wasm
+node_modules

src/wasm_package/browser/assert.js

@@ -0,0 +1,7 @@
+// Minimal shim for nodejs's assert module, for the browser
+// For some reason, this doesn't work with the https://github.com/browserify/commonjs-assert shim,
+// which causes the webpack bundle to hang when attempting to import it.
+
+export default function assert(val, err='assertion failed') {
+    if (!val) throw err
+}

src/wasm_package/build.sh

@@ -10,5 +10,7 @@ set -xeo pipefail
 # Build WASM (Elements is always enabled)
 (cd ../.. && ./tools/build_wasm.sh --enable-elements)
 mkdir -p libwally_wasm && cp ../../wally_dist/wallycore.{js,wasm} libwally_wasm/
-# Rename to force commonjs mode. See https://github.com/emscripten-core/emscripten/pull/17451
-mv libwally_wasm/wallycore.js libwally_wasm/wallycore.cjs
+touch libwally_wasm/index # necessary for webpack to work (fixes "Can't resolve './' in 'wasm_package/libwally_wasm'")
+
+# Build browser bundle (to dist/wallycore.bundle.js, see webpack.config.js)
+webpack --mode production

src/wasm_package/core.js

@@ -1,5 +1,5 @@
 import assert from 'assert'
-import InitWallyModule from './libwally_wasm/wallycore.cjs'
+import InitWallyModule from './libwally_wasm/wallycore.js'
 import { WALLY_OK, WALLY_ERROR, WALLY_EINVAL, WALLY_ENOMEM } from './const.js'
 
 // Initialize the underlying WASM module and expose it publicly