fix: listen on IPv4 loopback only by default on Windows (#4547)

Author: mrbbot

.changeset/quick-pens-develop.md

@@ -0,0 +1,7 @@
+---
+"wrangler": minor
+---
+
+fix: listen on IPv4 loopback only by default on Windows
+
+Due to a [known issue](https://github.com/cloudflare/workerd/issues/1408), `workerd` will only listen on the IPv4 loopback address `127.0.0.1` when it's asked to listen on `localhost`. On Node.js > 17, `localhost` will resolve to the IPv6 loopback address, meaning requests to `workerd` would fail. This change switches to using the IPv4 loopback address throughout Wrangler on Windows, while [workerd#1408](https://github.com/cloudflare/workerd/issues/1408) gets fixed.

packages/wrangler/src/__tests__/configuration.test.ts

@@ -30,7 +30,7 @@ describe("normalizeAndValidateConfig()", () => {
 			constellation: [],
 			hyperdrive: [],
 			dev: {
-				ip: "localhost",
+				ip: process.platform === "win32" ? "127.0.0.1" : "localhost",
 				local_protocol: "http",
 				port: undefined, // the default of 8787 is set at runtime
 				upstream_protocol: "https",

packages/wrangler/src/__tests__/dev.test.tsx

@@ -840,7 +840,7 @@ describe("wrangler dev", () => {
 			fs.writeFileSync("index.js", `export default {};`);
 			await runWrangler("dev");
 			expect((Dev as jest.Mock).mock.calls[0][0].initialIp).toEqual(
-				"localhost"
+				process.platform === "win32" ? "127.0.0.1" : "localhost"
 			);
 			expect(std.out).toMatchInlineSnapshot(`""`);
 			expect(std.warn).toMatchInlineSnapshot(`""`);
@@ -1060,7 +1060,7 @@ describe("wrangler dev", () => {
 			fs.writeFileSync("index.js", `export default {};`);
 			await runWrangler("dev");
 			expect((Dev as jest.Mock).mock.calls[0][0].initialIp).toEqual(
-				"localhost"
+				process.platform === "win32" ? "127.0.0.1" : "localhost"
 			);
 			expect(std.out).toMatchInlineSnapshot(`
 			        "Your worker has access to the following bindings:

packages/wrangler/src/config/validation.ts

@@ -390,7 +390,14 @@ function normalizeAndValidateDev(
 	rawDev: RawDevConfig
 ): DevConfig {
 	const {
-		ip = "localhost",
+		// On Windows, when specifying `localhost` as the socket hostname, `workerd`
+		// will only listen on the IPv4 loopback `127.0.0.1`, not the IPv6 `::1`:
+		// https://github.com/cloudflare/workerd/issues/1408
+		// On Node 17+, `fetch()` will only try to fetch the IPv6 address.
+		// For now, on Windows, we default to listening on IPv4 only and using
+		// `127.0.0.1` when sending control requests to `workerd` (e.g. with the
+		// `ProxyController`).
+		ip = process.platform === "win32" ? "127.0.0.1" : "localhost",
 		port,
 		inspector_port,
 		local_protocol = "http",

packages/wrangler/src/pages/dev.ts

@@ -99,7 +99,14 @@ export function Options(yargs: CommonYargsArgv) {
 			},
 			ip: {
 				type: "string",
-				default: "localhost",
+				// On Windows, when specifying `localhost` as the socket hostname,
+				// `workerd` will only listen on the IPv4 loopback `127.0.0.1`, not the
+				// IPv6 `::1`: https://github.com/cloudflare/workerd/issues/1408
+				// On Node 17+, `fetch()` will only try to fetch the IPv6 address.
+				// For now, on Windows, we default to listening on IPv4 only and using
+				// `127.0.0.1` when sending control requests to `workerd` (e.g. with the
+				// `ProxyController`).
+				default: process.platform === "win32" ? "127.0.0.1" : "localhost",
 				description: "The IP address to listen on",
 			},
 			port: {