Pass type: "module" to new Worker() (#2426)

* Pass `type: "module"` to `new Worker()`

* PR number

* More tweaks

Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>

bin/wasm-node/CHANGELOG.md

@@ -4,6 +4,7 @@
 
 ### Changed
 
+- `new Worker` is now called with the `{ type: "module" }` option. Despite not being supported by NodeJS or Firefox, indicating this option is technically more correct and is necessary in order for smoldot to run with Deno. ([#2426](https://github.com/paritytech/smoldot/pull/2426))
 - When a database and a chain specification checkpoint are both provided to `addChain`, the block in the database is used only if it has a higher block number than the block in the chain specification checkpoint. This makes it possible to bypass issues where smoldot is incapable of syncing over a certain block by updating the chain specification, without having to manually clear existing databases. ([#2401](https://github.com/paritytech/smoldot/pull/2401))
 
 ### Fixed

bin/wasm-node/javascript/README.md

@@ -77,7 +77,7 @@ The code in this package uses a web worker (in browsers) or a worker thread (on
 line of JavaScript that creates the worker is of the following form:
 
 ``` js
-new Worker(new URL('./worker.js', import.meta.url));
+new Worker(new URL('./worker.js', import.meta.url), { type: "module" });
 ```
 
 This format is compatible [with Webpack 5](https://webpack.js.org/guides/web-workers/), meaning

bin/wasm-node/javascript/src/worker/spawn-browser-overwrite.js

@@ -24,6 +24,16 @@ export default function () {
     // Because this line is precisely recognized by bundlers, we extract it to a separate
     // JavaScript file.
     // See also the README.md for more context.
-    const worker = new Worker(new URL('./worker.js', import.meta.url), { name: "smoldot" });
+
+    // Note that, at the time of writing, Firefox doesn't support the `type: "module"` option.
+    // Because browsers don't fully support modules yet, this code is expected to be run through
+    // a bundler (e.g. WebPack) before being given to a browser, which will remove all usage of
+    // modules in the worker code. It is thus also the role of this bundler to tweak or remove
+    // the value of this `type` property to indicate to the browser that modules aren't in use.
+    //
+    // WebPack in particular does this, but it is unclear whether *all* bundlers do it.
+    // Whether bundlers actually do this or not, it is nonetheless more correct to indicate
+    // `type: "module"` and doing so doesn't have any drawback.
+    const worker = new Worker(new URL('./worker.js', import.meta.url), { name: "smoldot", type: "module" });
     return worker;
 }

bin/wasm-node/javascript/src/worker/spawn.js

@@ -23,6 +23,10 @@ export default function () {
     // Because this line is precisely recognized by bundlers, we extract it to a separate
     // JavaScript file.
     // See also the README.md for more context.
-    const worker = new Worker(new URL('./worker.js', import.meta.url));
+
+    // Note that at the time of writing of this comment, NodeJS doesn't support the
+    // `type: "module"` option, as modules "just work". But we put it anyway because Deno throws
+    // an exception if this option isn't present.
+    const worker = new Worker(new URL('./worker.js', import.meta.url), { type: "module" });
     return worker;
 }