V3 Backport [#10004]: fix wrangler dev logs being logged on the incorrect level in some cases

.changeset/deep-lizards-move.md

@@ -0,0 +1,35 @@
+---
+"wrangler": patch
+---
+
+fix `wrangler dev` logs being logged on the incorrect level in some cases
+
+currently the way `wrangler dev` prints logs is faulty, for example the following code
+
+```js
+console.error("this is an error");
+console.warn("this is a warning");
+console.debug("this is a debug");
+```
+
+inside a worker would cause the following logs:
+
+```text
+✘ [ERROR] this is an error
+
+✘ [ERROR] this is a warning
+
+this is a debug
+```
+
+(note that the warning is printed as an error and the debug log is printed even if by default it should not)
+
+the changes here make sure that the logs are instead logged to their correct level, so for the code about the following will be logged instead:
+
+```text
+✘ [ERROR] this is an error
+
+▲ [WARNING] this is a warning
+```
+
+(running `wrangler dev` with the `--log-level=debug` flag will also cause the debug log to be included as well)

.changeset/full-areas-lick.md

@@ -0,0 +1,7 @@
+---
+"miniflare": minor
+---
+
+add `structuredWorkerdLogs` option
+
+add a new top-level option named `structuredWorkerdLogs` that makes workerd print to stdout structured logs (stringified jsons of the following shape: `{ timestamp: number, level: string, message: string }`) instead of printing logs to stdout and stderr

fixtures/shared/src/run-wrangler-long-lived.ts

@@ -87,7 +87,9 @@ async function runLongLivedWrangler(
 		chunks.push(chunk);
 	});
 	wranglerProcess.stderr?.on("data", (chunk) => {
-		console.log(`[${command}]`, chunk.toString());
+		if (process.env.WRANGLER_LOG === "debug") {
+			console.log(`[${command}]`, chunk.toString());
+		}
 		chunks.push(chunk);
 	});
 	wranglerProcess.once("exit", (exitCode) => {

fixtures/worker-logs/package.json

@@ -0,0 +1,22 @@
+{
+	"name": "@fixture/worker-logs",
+	"private": true,
+	"scripts": {
+		"check:type": "tsc",
+		"dev": "pnpm dev.module",
+		"dev.module": "wrangler dev -c wrangler.module.jsonc",
+		"dev.service": "wrangler dev -c wrangler.service.jsonc",
+		"start": "pnpm dev.module",
+		"test:ci": "vitest run",
+		"test:watch": "vitest"
+	},
+	"devDependencies": {
+		"@cloudflare/workers-tsconfig": "workspace:^",
+		"typescript": "catalog:default",
+		"vitest": "catalog:default",
+		"wrangler": "workspace:*"
+	},
+	"volta": {
+		"extends": "../../package.json"
+	}
+}

fixtures/worker-logs/src/module.js

@@ -0,0 +1,25 @@
+export default {
+	async fetch(request, env) {
+		const response = new Response("Hello");
+
+		const customMessage = request.headers.get("x-custom-message");
+		if (customMessage) {
+			if (customMessage === "%__VERY_VERY_LONG_MESSAGE_%") {
+				// We can't simply pass a huge long message as a header thus
+				// why a placeholder is used here
+				console.log("z".repeat(2 ** 20));
+			} else {
+				console.log(customMessage);
+			}
+			return response;
+		}
+
+		console.log("<<<<<this is a log>>>>>");
+		console.warn("<<<<<this is a warning>>>>>");
+		console.error("<<<<<this is an error>>>>>");
+		console.debug("<<<<<this is a debug message>>>>>");
+		console.info("<<<<<this is an info message>>>>>");
+
+		return response;
+	},
+};

fixtures/worker-logs/src/service.js

@@ -0,0 +1,12 @@
+async function handler(request) {
+	console.log("<<<<<this is a log>>>>>");
+	console.warn("<<<<<this is a warning>>>>>");
+	console.error("<<<<<this is an error>>>>>");
+	console.debug("<<<<<this is a debug message>>>>>");
+	console.info("<<<<<this is an info message>>>>>");
+	return new Response("Hello");
+}
+
+addEventListener("fetch", (event) => {
+	event.respondWith(handler(event.request));
+});