feat(wrangler): WIP

packages/wrangler/src/deployment-bundle/entry.ts

@@ -55,13 +55,10 @@ export async function getEntry(
 				? path.resolve(config.site?.["entry-point"])
 				: // site.entry-point could be a directory
 					path.resolve(config.site?.["entry-point"], "index.js");
-		} else if (
-			args.legacyAssets ||
-			config.legacy_assets ||
-			args.experimentalAssets ||
-			config.experimental_assets
-		) {
+		} else if (args.legacyAssets || config.legacy_assets) {
 			file = path.resolve(getBasePath(), "templates/no-op-worker.js");
+		} else if (args.experimentalAssets || config.experimental_assets) {
+			file = path.resolve(getBasePath(), "templates/no-op-assets-worker.ts");
 		} else {
 			throw new UserError(
 				`Missing entry-point: The entry-point should be specified via the command line (e.g. \`wrangler ${command} path/to/script\`) or the \`main\` config field.`

packages/wrangler/src/dev.tsx

@@ -877,6 +877,7 @@ export async function startDev(args: StartDevOptions) {
 					}
 					legacyAssetPaths={legacyAssetPaths}
 					legacyAssetsConfig={configParam.legacy_assets}
+					experimentalAssets={experimentalAssets}
 					initialPort={
 						args.port ?? configParam.dev.port ?? (await getLocalPort())
 					}
@@ -1039,6 +1040,8 @@ export async function startApiDev(args: StartDevOptions) {
 				args.accountId ?? configParam.account_id ?? getAccountFromCache()?.id,
 			legacyAssetPaths: legacyAssetPaths,
 			legacyAssetsConfig: configParam.legacy_assets,
+			// TODO @Carmen can/should we pass this via configParam?
+			experimentalAssets: undefined,
 			//port can be 0, which means to use a random port
 			initialPort: args.port ?? configParam.dev.port ?? (await getLocalPort()),
 			initialIp: args.ip ?? configParam.dev.ip,

packages/wrangler/src/dev/local.tsx

@@ -2,6 +2,7 @@ import assert from "node:assert";
 import chalk from "chalk";
 import { useEffect, useRef } from "react";
 import onExit from "signal-exit";
+import { ExperimentalAssets } from "../config/environment";
 import { registerWorker } from "../dev-registry";
 import { logger } from "../logger";
 import { DEFAULT_WORKER_NAME, MiniflareServer } from "./miniflare";
@@ -31,6 +32,7 @@ export interface LocalProps {
 	bindings: CfWorkerInit["bindings"];
 	workerDefinitions: WorkerRegistry | undefined;
 	legacyAssetPaths: LegacyAssetPaths | undefined;
+	experimentalAssets: ExperimentalAssets | undefined;
 	initialPort: number | undefined;
 	initialIp: string;
 	rules: Config["rules"];
@@ -90,6 +92,7 @@ export async function localPropsToConfigBundle(
 		bindings: props.bindings,
 		workerDefinitions: props.workerDefinitions,
 		legacyAssetPaths: props.legacyAssetPaths,
+		experimentalAssets: props.experimentalAssets,
 		initialPort: props.initialPort,
 		initialIp: props.initialIp,
 		rules: props.rules,

packages/wrangler/src/dev/miniflare.ts

@@ -1,6 +1,6 @@
 import assert from "node:assert";
 import { randomUUID } from "node:crypto";
-import path from "node:path";
+import path, { resolve } from "node:path";
 import * as esmLexer from "es-module-lexer";
 import {
 	CoreHeaders,
@@ -16,6 +16,7 @@ import {
 	EXTERNAL_AI_WORKER_NAME,
 	EXTERNAL_AI_WORKER_SCRIPT,
 } from "../ai/fetcher";
+import { ExperimentalAssets } from "../config/environment";
 import { ModuleTypeToRuleType } from "../deployment-bundle/module-collection";
 import { withSourceURLs } from "../deployment-bundle/source-url";
 import { UserError } from "../errors";
@@ -172,6 +173,7 @@ export interface ConfigBundle {
 	bindings: CfWorkerInit["bindings"];
 	workerDefinitions: WorkerRegistry | undefined;
 	legacyAssetPaths: LegacyAssetPaths | undefined;
+	experimentalAssets: ExperimentalAssets | undefined;
 	initialPort: Port;
 	initialIp: string;
 	rules: Config["rules"];
@@ -374,7 +376,7 @@ type MiniflareBindingsConfig = Pick<
 	| "services"
 	| "serviceBindings"
 > &
-	Partial<Pick<ConfigBundle, "format" | "bundle">>;
+	Partial<Pick<ConfigBundle, "format" | "bundle" | "experimentalAssets">>;
 
 // TODO(someday): would be nice to type these methods more, can we export types for
 //  each plugin options schema and use those
@@ -408,7 +410,9 @@ export function buildMiniflareBindingOptions(config: MiniflareBindingsConfig): {
 	// Setup service bindings to external services
 	const serviceBindings: NonNullable<WorkerOptions["serviceBindings"]> = {
 		...config.serviceBindings,
+		...(config.experimentalAssets ? { ASSET_SERVER: "asset-server" } : {}),
 	};
+
 	const notFoundServices = new Set<string>();
 	for (const service of config.services ?? []) {
 		if (service.service === config.name) {
@@ -837,6 +841,32 @@ export async function buildMiniflareOptions(
 		}
 	}
 
+	// TODO @Carmen can we read the toml config instead?
+	const assetServerWorker: WorkerOptions | undefined = config.experimentalAssets
+		? {
+				name: "asset-server",
+				compatibilityDate: "2024-01-01",
+				compatibilityFlags: ["nodejs_compat"],
+				modulesRoot: resolve(
+					"../../packages/workers-shared/asset-server-worker/src/index.ts"
+				),
+				modules: [
+					{
+						type: "ESModule",
+						path: resolve(
+							"../../packages/workers-shared/asset-server-worker/src/index.ts"
+						),
+					},
+				],
+				unsafeDirectSockets: [
+					{
+						host: "127.0.0.1",
+						port: 0,
+					},
+				],
+			}
+		: undefined;
+
 	const upstream =
 		typeof config.localUpstream === "string"
 			? `${config.upstreamProtocol}://${config.localUpstream}`
@@ -879,6 +909,9 @@ export async function buildMiniflareOptions(
 					proxy: true,
 				})),
 			},
+			...(config.experimentalAssets
+				? [assetServerWorker as WorkerOptions]
+				: []),
 			...externalWorkers,
 		],
 	};
@@ -947,9 +980,11 @@ export class MiniflareServer extends TypedEventTarget<MiniflareServerEventMap> {
 					config,
 					this.#proxyToUserWorkerAuthenticationSecret
 				);
+
 			if (opts?.signal?.aborted) {
 				return;
 			}
+
 			if (this.#mf === undefined) {
 				this.#mf = new Miniflare(options);
 			} else {
@@ -981,6 +1016,7 @@ export class MiniflareServer extends TypedEventTarget<MiniflareServerEventMap> {
 			this.dispatchEvent(new ErrorEvent("error", { error }));
 		}
 	}
+
 	onBundleUpdate(config: ConfigBundle, opts?: Abortable): Promise<void> {
 		return this.#mutex.runWith(() => this.#onBundleUpdate(config, opts));
 	}

packages/wrangler/templates/no-op-assets-worker.ts

@@ -0,0 +1,31 @@
+/**
+ * This Worker is used as a default entry-point for Assets-only
+ * Workers. It proxies the request directly on to the Asset Sever
+ * Worker service binding.
+ *
+ * In an Assets-only Workers world, we want to enable users
+ * to deploy a Worker with Assets without ever having to provide
+ * a User Worker.
+ *
+ * ```bash
+ * wrangler dev --experimental-assets dist
+ * wrangler deploy --experimental-assets dist
+ * ```
+ *
+ * ```toml
+ * name = "assets-only-worker"
+ * compatibility_date = "2024-01-01"
+ * ```
+ *
+ * Without a user-defined Worker, which usually serves as the entry
+ * point in the bundling process, wrangler needs to default to some
+ * other entry-point Worker for all intents and purposes. This is what
+ * this Worker is.
+ */
+
+export default {
+	async fetch(request: Request, env) {
+		const response = await env.ASSET_SERVER.fetch(request.url, request);
+		return new Response(response.body, response);
+	},
+};