Don't crash Vitest when started with a non-existent tail consumer (#9350)

* Don't crash Vitest when started with a non-existent tail consumer

* Create warm-dingos-lay.md

Author: penalosa

.changeset/warm-dingos-lay.md

@@ -0,0 +1,5 @@
+---
+"@cloudflare/vitest-pool-workers": patch
+---
+
+Don't crash Vitest when started with a non-existent tail consumer

fixtures/vitest-pool-workers-examples/multiple-workers/api-service/wrangler.jsonc

@@ -12,4 +12,8 @@
 			"service": "database-service",
 		},
 	],
+	"tail_consumers": [
+		{ "service": "this-tail-does-not-exist" },
+		{ "service": "tail-consumer" },
+	],
 }

fixtures/vitest-pool-workers-examples/multiple-workers/vitest.config.ts

@@ -94,6 +94,23 @@ export default defineWorkersProject({
 							compatibilityFlags: ["nodejs_compat"],
 							kvNamespaces: ["KV_NAMESPACE"],
 						},
+						{
+							name: "tail-consumer",
+							modules: [
+								{
+									path: "index.js",
+									type: "ESModule",
+									contents: /* javascript */ `
+										export default {
+											tail(event) {
+											console.log("tail event received")
+											}
+										}
+										`,
+								},
+							],
+							compatibilityDate: "2024-01-01",
+						},
 					],
 				},
 			},

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

@@ -139,6 +139,38 @@ function parseWorkerOptions(
 
 const log = new Log(LogLevel.WARN, { prefix: "vpw" });
 
+function filterTails(
+	tails: WorkerOptions["tails"],
+	userWorkers?: { name?: string }[]
+) {
+	// Only connect the tail consumers that represent Workers that are defined in the Vitest config. Warn that a tail will be omitted otherwise
+	// This _differs from service bindings_ because tail consumers are "optional" in a sense, and shouldn't affect the runtime behaviour of a Worker
+	return tails?.filter((tailService) => {
+		let name: string;
+		if (typeof tailService === "string") {
+			name = tailService;
+		} else if (
+			typeof tailService === "object" &&
+			"name" in tailService &&
+			typeof tailService.name === "string"
+		) {
+			name = tailService.name;
+		} else {
+			// Don't interfere with network-based tail connections (e.g. via the dev registry), or kCurrentWorker
+			return true;
+		}
+		const found = userWorkers?.some((w) => w.name === name);
+
+		if (!found) {
+			log.warn(
+				`Tail consumer "${name}" was not found in your config. Make sure you add it if you'd like to simulate receiving tail events locally.`
+			);
+		}
+
+		return found;
+	});
+}
+
 async function parseCustomPoolOptions(
 	rootPath: string,
 	value: unknown,
@@ -243,6 +275,11 @@ async function parseCustomPoolOptions(
 			options.miniflare as SourcelessWorkerOptions
 		);
 
+		options.miniflare = {
+			...options.miniflare,
+			tails: filterTails(workerOptions.tails, options.miniflare.workers),
+		};
+
 		// Record any Wrangler `define`s
 		options.defines = define;
 	}