fix(vitest-pool-workers): enable dependency pre-bundling

.changeset/gold-frogs-rest.md

@@ -0,0 +1,29 @@
+---
+"@cloudflare/vitest-pool-workers": patch
+---
+
+Added [Vite dependency pre-bundling](https://vite.dev/guide/dep-pre-bundling) support. If you encounter module resolution issues—such as: `Error: Cannot use require() to import an ES Module` or `Error: No such module`—you can now bundle these dependencies using the [deps.optimizer](https://vitest.dev/config/#deps-optimizer) option:
+
+```tsx
+import { defineWorkersConfig } from "@cloudflare/vitest-pool-workers/config";
+
+export default defineWorkersConfig({
+	test: {
+		deps: {
+			optimizer: {
+				ssr: {
+					enabled: true,
+					include: ["your-package-name"],
+				},
+			},
+		},
+		poolOptions: {
+			workers: {
+				// ...
+			},
+		},
+	},
+});
+```
+
+Fixed #6591, #6581, #6405.

fixtures/vitest-pool-workers-examples/module-resolution/README.md

@@ -0,0 +1,34 @@
+# ⚡ module-resolution
+
+This fixture demonstrates that the Vitest integration correctly resolves modules, including:
+
+- A CommonJS package that requires a directory rather than a specific file.
+- A package without a main entrypoint or with browser field mapping, handled via [Dependency Pre-Bundling](#dependency-pre-bundling).
+
+## Dependency Pre-Bundling
+
+[Dependency Pre-Bundling](https://vite.dev/guide/dep-pre-bundling) is a Vite feature that converts dependencies shipped as CommonJS or UMD into ESM. If you encounter module resolution issues—such as: `Error: Cannot use require() to import an ES Module` or `Error: No such module`—you can pre-bundle these dependencies using the [deps.optimizer](https://vitest.dev/config/#deps-optimizer) option:
+
+```ts
+import { defineWorkersConfig } from "@cloudflare/vitest-pool-workers/config";
+
+export default defineWorkersConfig({
+	test: {
+		deps: {
+			optimizer: {
+				ssr: {
+					enabled: true,
+					include: ["your-package-name"],
+				},
+			},
+		},
+		poolOptions: {
+			workers: {
+				// ...
+			},
+		},
+	},
+});
+```
+
+See our [vitest config](./vitest.config.ts) for an example of how we pre-bundled `discord-api-types/v10` and `@microlabs/otel-cf-workers`.

fixtures/vitest-pool-workers-examples/external-package-resolution/src/index.ts → fixtures/vitest-pool-workers-examples/module-resolution/src/index.ts

@@ -1,4 +1,10 @@
 import { Toucan } from "toucan-js";
+// Testing dependency without a main entrypoint
+// @see https://github.com/cloudflare/workers-sdk/issues/6591
+import "discord-api-types/v10";
+// Testing dependency with browser field mapping
+// @see https://github.com/cloudflare/workers-sdk/issues/6581
+import "@microlabs/otel-cf-workers";
 
 export default {
 	async fetch(): Promise<Response> {

fixtures/vitest-pool-workers-examples/module-resolution/test/index.spec.ts

@@ -0,0 +1,20 @@
+import { instrument } from "@microlabs/otel-cf-workers";
+import { Utils } from "discord-api-types/v10";
+import dep from "ext-dep";
+import { assert, describe, test } from "vitest";
+
+describe("test", () => {
+	test("resolves commonjs directory dependencies correctly", async () => {
+		assert.equal(dep, 123);
+	});
+
+	// This requires the `deps.optimizer` option to be set in the vitest config
+	test("resolves dependency without a default entrypoint", async () => {
+		assert.isFunction(Utils.isDMInteraction);
+	});
+
+	// This requires the `deps.optimizer` option to be set in the vitest config
+	test("resolves dependency with mapping on the browser field", async () => {
+		assert.isFunction(instrument);
+	});
+});

fixtures/vitest-pool-workers-examples/internal-module-resolution/vitest.config.ts → fixtures/vitest-pool-workers-examples/module-resolution/vitest.config.ts

@@ -2,6 +2,14 @@ import { defineWorkersProject } from "@cloudflare/vitest-pool-workers/config";
 
 export default defineWorkersProject({
 	test: {
+		deps: {
+			optimizer: {
+				ssr: {
+					enabled: true,
+					include: ["discord-api-types/v10", "@microlabs/otel-cf-workers"],
+				},
+			},
+		},
 		poolOptions: {
 			workers: {
 				wrangler: { configPath: "./wrangler.toml" },

fixtures/vitest-pool-workers-examples/external-package-resolution/wrangler.toml → fixtures/vitest-pool-workers-examples/module-resolution/wrangler.toml

@@ -1,3 +1,3 @@
-name = "external-package-resolution"
+name = "module-resolution"
 main = "src/index.ts"
 compatibility_date = "2024-04-05"

fixtures/vitest-pool-workers-examples/package.json

@@ -13,13 +13,16 @@
 	"devDependencies": {
 		"@cloudflare/vitest-pool-workers": "workspace:*",
 		"@cloudflare/workers-types": "^4.20250204.0",
+		"@microlabs/otel-cf-workers": "1.0.0-rc.45",
 		"@types/node": "catalog:default",
-		"ext-dep": "file:./internal-module-resolution/vendor/ext-dep",
+		"discord-api-types": "0.37.98",
+		"ext-dep": "file:./module-resolution/vendor/ext-dep",
 		"jose": "^5.2.2",
 		"miniflare": "workspace:*",
 		"run-script-os": "^1.1.6",
-		"toucan-js": "^3.3.1",
+		"toucan-js": "3.4.0",
 		"typescript": "catalog:default",
+		"vite": "catalog:default",
 		"vitest": "catalog:default",
 		"wrangler": "workspace:*"
 	},

package.json

@@ -49,7 +49,7 @@
 		"tree-kill": "^1.2.2",
 		"turbo": "^2.2.3",
 		"typescript": "catalog:default",
-		"vite": "^5.0.12",
+		"vite": "catalog:default",
 		"vitest": "catalog:default"
 	},
 	"packageManager": "[email protected]",

packages/vitest-pool-workers/src/config/index.ts

@@ -1,8 +1,10 @@
 import assert from "node:assert";
 import crypto from "node:crypto";
 import fs from "node:fs/promises";
+import { builtinModules } from "node:module";
 import path from "node:path";
 import { MessageChannel, receiveMessageOnPort } from "node:worker_threads";
+import { workerdBuiltinModules } from "../shared/builtin-modules";
 import type {
 	WorkersConfigPluginAPI,
 	WorkersPoolOptions,
@@ -147,6 +149,17 @@ function createConfigPlugin(): Plugin<WorkersConfigPluginAPI> {
 			// https://github.com/vitejs/vite/blob/v5.1.4/packages/vite/src/node/plugins/resolve.ts#L175
 			config.ssr.target = "webworker";
 
+			// Pre-bundling dependencies with vite
+			config.test.deps ??= {};
+			config.test.deps.optimizer ??= {};
+			config.test.deps.optimizer.ssr ??= {};
+			config.test.deps.optimizer.ssr.enabled ??= true;
+			config.test.deps.optimizer.ssr.exclude ??= [];
+			ensureArrayIncludes(config.test.deps.optimizer.ssr.exclude, [
+				...workerdBuiltinModules,
+				...builtinModules.concat(builtinModules.map((m) => `node:${m}`)),
+			]);
+
 			// Ideally, we would force `pool` to be @cloudflare/vitest-pool-workers here,
 			// but the tests in `packages/vitest-pool-workers` define `pool` as "../..".
 			config.test.pool ??= "@cloudflare/vitest-pool-workers";

packages/vitest-pool-workers/src/pool/index.ts

@@ -23,6 +23,7 @@ import {
 } from "miniflare";
 import semverSatisfies from "semver/functions/satisfies.js";
 import { createMethodsRPC } from "vitest/node";
+import { workerdBuiltinModules } from "../shared/builtin-modules";
 import { createChunkingSocket } from "../shared/chunking-socket";
 import { CompatibilityFlagAssertions } from "./compatibility-flag-assertions";
 import { OPTIONS_PATH, parseProjectOptions } from "./config";
@@ -41,7 +42,6 @@ import {
 import {
 	ensurePosixLikePath,
 	handleModuleFallbackRequest,
-	workerdBuiltinModules,
 } from "./module-fallback";
 import type {
 	SourcelessWorkerOptions,

packages/vitest-pool-workers/src/pool/module-fallback.ts

@@ -8,6 +8,7 @@ import util from "node:util";
 import * as cjsModuleLexer from "cjs-module-lexer";
 import { buildSync } from "esbuild";
 import { ModuleRuleTypeSchema, Response } from "miniflare";
+import { workerdBuiltinModules } from "../shared/builtin-modules";
 import { isFileNotFoundError } from "./helpers";
 import type { ModuleRuleType, Request, Worker_Module } from "miniflare";
 import type { ViteDevServer } from "vite";
@@ -41,6 +42,19 @@ function trimSuffix(suffix: string, value: string) {
 	return value.substring(0, value.length - suffix.length);
 }
 
+/**
+ * When pre-bundling is enabled, Vite will add a hash to the end of the file path
+ * e.g. `/node_modules/.vite/deps/my-dep.js?v=f3sf2ebd`
+ *
+ * @see https://vite.dev/guide/features.html#npm-dependency-resolving-and-pre-bundling
+ * @see https://github.com/cloudflare/workers-sdk/pull/5673
+ */
+const versionHashRegExp = /\?v=[0-9a-f]+$/;
+
+function trimViteVersionHash(filePath: string) {
+	return filePath.replace(versionHashRegExp, "");
+}
+
 // RegExp for path suffix to force loading module as specific type.
 // (e.g. `/path/to/module.wasm?mf_vitest_force=CompiledWasm`)
 // This suffix will be added by the pool when fetching a module that matches a
@@ -54,12 +68,6 @@ const forceModuleTypeRegexp = new RegExp(
 	`\\?mf_vitest_force=(${ModuleRuleTypeSchema.options.join("|")})$`
 );
 
-// Node.js built-in modules provided by `workerd`
-export const workerdBuiltinModules = new Set([
-	...VITEST_POOL_WORKERS_DEFINE_BUILTIN_MODULES,
-	"__STATIC_CONTENT_MANIFEST",
-]);
-
 // `chai` contains circular `require()`s which aren't supported by `workerd`
 // TODO(someday): support circular `require()` in `workerd`
 const bundleDependencies = ["chai"];
@@ -323,7 +331,8 @@ async function viteResolve(
 		//       (Specifically, the "tinyrainbow" module imports `node:tty` as `tty`)
 		return id;
 	}
-	return resolved.id;
+
+	return trimViteVersionHash(resolved.id);
 }
 
 type ResolveMethod = "import" | "require";
@@ -565,6 +574,11 @@ export async function handleModuleFallbackRequest(
 		return await load(vite, logBase, method, target, specifier, filePath);
 	} catch (e) {
 		debuglog(logBase, "error:", e);
+		console.error(
+			`[vitest-pool-workers] Failed to ${method} ${JSON.stringify(target)} from ${JSON.stringify(referrer)}.`,
+			"To resolve this, try bundling the relevant dependency with Vite.",
+			"For more details, refer to https://developers.cloudflare.com/workers/testing/vitest-integration/known-issues/#module-resolution"
+		);
 	}
 
 	return new Response(null, { status: 404 });

packages/vitest-pool-workers/src/shared/builtin-modules.ts

@@ -0,0 +1,5 @@
+// Node.js built-in modules provided by `workerd`
+export const workerdBuiltinModules = new Set([
+	...VITEST_POOL_WORKERS_DEFINE_BUILTIN_MODULES,
+	"__STATIC_CONTENT_MANIFEST",
+]);

packages/vitest-pool-workers/tsconfig.emit.json

@@ -8,5 +8,5 @@
 		"incremental": false
 	},
 	// Only want to emit `.d.ts` for `/config` sub-export
-	"include": ["./src/config/**/*.ts"]
+	"include": ["./src/shared/types-global.d.ts", "./src/config/**/*.ts"]
 }

packages/workers-editor-shared/package.json

@@ -42,7 +42,7 @@
 		"eslint": "^8.49.0",
 		"react": "^18.3.1",
 		"react-dom": "^18.3.1",
-		"vite": "^5.0.12",
+		"vite": "catalog:default",
 		"vite-plugin-dts": "^4.0.1"
 	},
 	"peerDependencies": {