Load the Emscripten glue through an indirection

Metro refuses a non-literal import() at build time, and the webpackIgnore
comment that was there to excuse it does not survive babel-preset-expo,
which strips it before Metro's dependency collector ever sees it. So an
Expo web app did not fail against this package at runtime, it failed to
build at all, and every such consumer had to patch the published dist to
get past it.

Putting the call inside a string leaves nothing for a bundler to parse and
nothing to strip. It needs unsafe-eval, which is why importGlue stays the
documented way out for a page under a strict CSP.

The docstring above it claimed bundlers chunk the glue. They never did,
since webpackIgnore told them not to.

Author: PetkoKuzmanov

CHANGELOG.md

@@ -16,7 +16,7 @@ surprised by it.
 
 ### Fixed before publishing
 
-Two things that would each have made this release wrong.
+Three things that would each have made this release wrong.
 
 The binary shipped Helvetica, baked into `viro-web.data` by the preload step and
 therefore redistributed with the package. It renders in **Roboto** now, which is
@@ -30,6 +30,15 @@ existed in `types.ts` and in no build. Every one of them would have been
 `undefined` at runtime. Rebuilt from virocore; the package's own test now
 checks all 126, and that the preloaded font is one this package may ship.
 
+And the glue module could not be bundled by Metro. `loadViroWebModule` reached
+it through a variable specifier, which Metro refuses at build time, and the
+`webpackIgnore` comment that was there to excuse it is stripped by
+`babel-preset-expo` before Metro's dependency collector runs. So an Expo web app
+did not fail at runtime against this package, it failed to build at all. The
+import goes through an indirection now, which no bundler parses. That
+indirection needs `unsafe-eval`, so a page under a strict CSP should pass
+`importGlue` instead.
+
 ### Added
 
 - **The tracking engine ships with the package.** Web AR needed a second WASM

src/loader.ts

@@ -22,8 +22,8 @@ function resolveAssetBase(baseUrl?: string): string {
 /**
  * Load and instantiate the WASM renderer module.
  *
- * The Emscripten glue (viro-web.js) is imported dynamically so bundlers treat it
- * as an async chunk and the ~2MB payload is only fetched on demand. The
+ * The Emscripten glue (viro-web.js) is fetched from the asset base at runtime
+ * rather than bundled, so the ~2MB payload is only paid for on demand. The
  * .wasm/.data sidecars are located from the same base (see resolveAssetBase).
  */
 export interface LoadOptions {
@@ -50,7 +50,12 @@ export async function loadViroWebModule(
     imported = await opts.importGlue();
   } else {
     const glueUrl = base + "viro-web.js";
-    imported = await import(/* webpackIgnore: true */ /* @vite-ignore */ glueUrl);
+    // Indirect so no bundler parses a non-literal import(). Metro rejects one
+    // outright, and strips the webpackIgnore comment before it would help.
+    const importModule = new Function("u", "return import(u)") as (
+      u: string,
+    ) => Promise<{ default?: ViroWebModuleFactory } | ViroWebModuleFactory>;
+    imported = await importModule(glueUrl);
   }
 
   const factory = ((imported as { default?: ViroWebModuleFactory }).default ??