feat(wasm): support output esm imports

src/presets/cloudflare.ts

@@ -22,5 +22,15 @@
         JSON.stringify({ lockfileVersion: 1 }, null, 2)
       );
     },
+    "rollup:before"(nitro) {
+      if (nitro.options.experimental?.wasm) {
+        if (nitro.options.experimental.wasm === true) {
+          nitro.options.experimental.wasm = {};
+        }
+        // Cloudflare Workers requires WASM to be directly imported
+        // https://community.cloudflare.com/t/fixed-cloudflare-workers-slow-with-moderate-sized-webassembly-bindings/184668/3
+        nitro.options.experimental.wasm.directImport = true;
+      }
+    },
   },
 });

src/rollup/config.ts

@@ -18,12 +18,13 @@
 import { sanitizeFilePath, resolvePath } from "mlly";
 import unimportPlugin from "unimport/unplugin";
 import { hash } from "ohash";
-import type { Nitro, NitroStaticBuildFlags } from "../types";
+import type { Nitro, NitroStaticBuildFlags, WasmOptions } from "../types";
 import { resolveAliases } from "../utils";
 import { runtimeDir } from "../dirs";
 import { version } from "../../package.json";
 import { replace } from "./plugins/replace";
 import { virtual } from "./plugins/virtual";
+import { wasmImport } from "./plugins/wasm-import";
 import { dynamicRequire } from "./plugins/dynamic-require";
 import { NodeExternalsOptions, externals } from "./plugins/externals";
 import { externals as legacyExternals } from "./plugins/externals-legacy";
@@ -150,9 +151,13 @@
   // WASM import support
   if (nitro.options.experimental.wasm) {
     const options = {
-      ...(nitro.options.experimental.wasm as RollupWasmOptions),
+      ...(nitro.options.experimental.wasm as WasmOptions),
     };
-    rollupConfig.plugins.push(wasmPlugin(options));
+    if (options.directImport) {
+      rollupConfig.plugins.push(wasmImport());
+    } else {
+      rollupConfig.plugins.push(wasmPlugin(options));
+    }
   }
 
   // Build-time environment variables
@@ -365,7 +370,8 @@
             return { id: _resolved, external: false };
           }
         }
-        if (!resolved || resolved.external) {
+        // @ts-expect-error cast
+        if (!resolved || (resolved.external && !resolved.__nitro_external__)) {
           throw new Error(
             `Cannot resolve ${JSON.stringify(id)} from ${JSON.stringify(
               from

src/rollup/plugins/wasm-import.ts

@@ -0,0 +1,69 @@
+import { createHash } from "node:crypto";
+import { extname, basename } from "node:path";
+import { promises as fs } from "node:fs";
+import type { Plugin } from "rollup";
+
+const PLUGIN_NAME = "nitro:wasm-import";
+const wasmRegex = /\.wasm$/;
+
+export function wasmImport(): Plugin {
+  const copies = Object.create(null);
+
+  return {
+    name: PLUGIN_NAME,
+    async resolveId(id: string, importer: string) {
+      if (copies[id]) {
+        return {
+          id: copies[id].publicFilepath,
+          external: true,
+        };
+      }
+      if (wasmRegex.test(id)) {
+        const { id: filepath } =
+          (await this.resolve(id, importer, { skipSelf: true })) || {};
+        console.log({ filepath });
+        if (!filepath || filepath === id) {
+          return null;
+        }
+        const buffer = await fs.readFile(filepath);
+        const hash = createHash("sha1")
+          .update(buffer)
+          .digest("hex")
+          .slice(0, 16);
+        const ext = extname(filepath);
+        const name = basename(filepath, ext);
+
+        const outputFileName = "wasm/[name]-[hash][extname]"
+          .replace(/\[hash]/g, hash)
+          .replace(/\[extname]/g, ext)
+          .replace(/\[name]/g, name);
+
+        const publicFilepath = `./${outputFileName}`;
+
+        copies[id] = {
+          filename: outputFileName,
+          publicFilepath,
+          buffer,
+        };
+
+        return {
+          id: publicFilepath,
+          external: true,
+        };
+      }
+    },
+    async generateBundle() {
+      await Promise.all(
+        Object.keys(copies).map(async (name) => {
+          const copy = copies[name];
+          await this.emitFile({
+            type: "asset",
+            source: copy.buffer,
+            name: "Rollup WASM Asset",
+            fileName: copy.filename,
+          });
+        })
+      );
+    },
+  };
+}

src/types/nitro.ts

@@ -180,6 +180,13 @@ export interface NitroRouteRules
   proxy?: { to: string } & ProxyOptions;
 }
 
+export interface WasmOptions extends RollupWasmOptions {
+  /**
+   * Direct import the wasm file instead of bundling, required in Cloudflare Workers
+   */
+  directImport?: boolean;
+}
+
 export interface NitroOptions extends PresetOptions {
   // Internal
   _config: NitroConfig;
@@ -216,7 +223,7 @@ export interface NitroOptions extends PresetOptions {
   serveStatic: boolean | "node" | "deno";
   noPublicDir: boolean;
   experimental?: {
-    wasm?: boolean | RollupWasmOptions;
+    wasm?: boolean | WasmOptions;
     legacyExternals?: boolean;
     openAPI?: boolean;
     /**