fix: start auxiliary web workers

CHANGELOG.md

@@ -2,6 +2,9 @@
 
 ## Unreleased
 
+- Start auxiliary WebAssembly workers through a generated module entry that
+  initializes their wasm-bindgen bindings.
+
 ## 0.1.13 - 2026-08-27
 
 - Build and publish configured auxiliary WebAssembly worker binaries in the

lib/rekindle/web/builder.ex

@@ -128,7 +128,8 @@ defmodule Rekindle.Web.Builder do
     with {:ok, cargo} <-
            Rekindle.Cargo.build_worker(project, target, worker, profile, cargo_options(options)),
          :ok <- create_worker_directory(directory),
-         :ok <- bindgen(wasm_bindgen, cargo.artifact, directory, "worker", options),
+         :ok <- bindgen(wasm_bindgen, cargo.artifact, directory, "bindings", options),
+         :ok <- write_worker_entry(directory),
          :ok <- ensure_worker(directory) do
       {:ok,
        %{
@@ -147,12 +148,26 @@ defmodule Rekindle.Web.Builder do
     end
   end
 
+  defp write_worker_entry(directory) do
+    path = Path.join(directory, "worker.js")
+    source = "import init from \"./bindings.js\";\n\nawait init();\n"
+
+    case File.write(path, source) do
+      :ok -> :ok
+      {:error, reason} -> file_error(:worker_entry, path, reason)
+    end
+  end
+
   defp ensure_worker(directory) do
     if File.regular?(Path.join(directory, "worker.js")) and
-         File.regular?(Path.join(directory, "worker_bg.wasm")) do
+         File.regular?(Path.join(directory, "bindings.js")) and
+         File.regular?(Path.join(directory, "bindings_bg.wasm")) do
       :ok
     else
-      error(:missing_worker, "wasm-bindgen did not produce worker.js and worker_bg.wasm")
+      error(
+        :missing_worker,
+        "the worker bootstrap or wasm-bindgen bindings are missing"
+      )
     end
   end
 

test/integration/development_test.exs

@@ -321,13 +321,14 @@ defmodule Rekindle.DevelopmentTest do
 
     worker = request("/@rekindle/web/#{generation}/workers/storage/worker.js", options)
     assert worker.status == 200
+    assert worker.resp_body == "import init from \"./bindings.js\";\n\nawait init();\n"
 
     assert Plug.Conn.get_resp_header(worker, "content-type") == [
              "text/javascript; charset=utf-8"
            ]
 
     worker_wasm =
-      request("/@rekindle/web/#{generation}/workers/storage/worker_bg.wasm", options)
+      request("/@rekindle/web/#{generation}/workers/storage/bindings_bg.wasm", options)
 
     assert worker_wasm.status == 200
     assert Plug.Conn.get_resp_header(worker_wasm, "content-type") == ["application/wasm"]
@@ -427,6 +428,38 @@ defmodule Rekindle.DevelopmentTest do
     refute Process.alive?(browser_process)
   end
 
+  test "starts a published auxiliary module worker in the browser", %{root: root} do
+    Application.put_env(:rekindle_development_test, Rekindle,
+      plugin: Rekindle.Plugin.Egui,
+      targets: [web: [], desktop: []]
+    )
+
+    publish_web(root, """
+    export default async function init() {
+      const worker = new Worker(
+        new URL("./workers/storage/worker.js", import.meta.url),
+        {type: "module"}
+      );
+      worker.addEventListener("message", async ({data}) => {
+        if (data === "worker-ready") {
+          await fetch("/__test/loaded/worker", {method: "POST"});
+        }
+      });
+    }
+    """)
+
+    {browser, url, browser_directory} = start_browser_server(root, :reload)
+    on_exit(fn -> File.rm_rf(browser_directory) end)
+
+    {browser_id, browser_process} = run_browser(browser, url, browser_directory)
+
+    assert_receive :browser_document_requested, @browser_start_timeout
+    assert_receive {:browser_loaded, "worker"}, 10_000
+    assert Process.alive?(browser_process)
+    assert :ok = stop_supervised(browser_id)
+    refute Process.alive?(browser_process)
+  end
+
   test "backs off repeated WebSocket connections that close before state arrives", %{root: root} do
     Application.put_env(:rekindle_development_test, Rekindle,
       plugin: Rekindle.Plugin.Egui,
@@ -642,11 +675,16 @@ defmodule Rekindle.DevelopmentTest do
 
     File.write!(
       Path.join(temporary, "workers/storage/worker.js"),
-      "export default async function init() {}"
+      "import init from \"./bindings.js\";\n\nawait init();\n"
+    )
+
+    File.write!(
+      Path.join(temporary, "workers/storage/bindings.js"),
+      "export default async function init() { postMessage(\"worker-ready\"); }"
     )
 
     File.write!(
-      Path.join(temporary, "workers/storage/worker_bg.wasm"),
+      Path.join(temporary, "workers/storage/bindings_bg.wasm"),
       <<0, 97, 115, 109>>
     )
 

test/integration/web_build_test.exs

@@ -159,7 +159,11 @@ defmodule Rekindle.WebBuildTest do
     assert File.regular?(Path.join(generation_root, "main.js"))
     assert File.regular?(Path.join(generation_root, "main_bg.wasm"))
     assert File.regular?(Path.join(generation_root, "workers/storage/worker.js"))
-    assert File.regular?(Path.join(generation_root, "workers/storage/worker_bg.wasm"))
+    assert File.regular?(Path.join(generation_root, "workers/storage/bindings.js"))
+    assert File.regular?(Path.join(generation_root, "workers/storage/bindings_bg.wasm"))
+
+    worker = File.read!(Path.join(generation_root, "workers/storage/worker.js"))
+    assert worker == "import init from \"./bindings.js\";\n\nawait init();\n"
 
     wrapper = File.read!(result.artifact)
     assert wrapper =~ ~s(import init from "./main.js";)
@@ -180,7 +184,8 @@ defmodule Rekindle.WebBuildTest do
     assert File.regular?(Path.join(generation_root, "main.js"))
     assert File.regular?(Path.join(generation_root, "main_bg.wasm"))
     assert File.regular?(Path.join(generation_root, "workers/storage/worker.js"))
-    assert File.regular?(Path.join(generation_root, "workers/storage/worker_bg.wasm"))
+    assert File.regular?(Path.join(generation_root, "workers/storage/bindings.js"))
+    assert File.regular?(Path.join(generation_root, "workers/storage/bindings_bg.wasm"))
 
     entry = File.read!(Path.join(root, "priv/static/rekindle/entry.js"))
     assert entry =~ "// Rekindle generation: #{result.metadata.generation}"
@@ -388,7 +393,7 @@ defmodule Rekindle.WebBuildTest do
       printf 'wasm' > "$output/${out_name}_bg.wasm"
       exit 0
     fi
-    if [ "$mode" = "missing-worker" ] && [ "$out_name" = "worker" ]; then
+    if [ "$mode" = "missing-worker" ] && [ "$out_name" = "bindings" ]; then
       exit 0
     fi
     printf "const wasm = new URL('${out_name}_bg.wasm', import.meta.url);\\n/* %s */\\nexport default async function init() { return wasm; }\\n" "$mode" > "$output/${out_name}.js"