fix(wrangler): Fix pages dev watch mode [_worker.js] (#6150)

* fix(wrangler): Fix `pages dev` watch mode [_worker.js]

The watch mode in `pages dev` for Advanced Mode projects
is currently partially broken, as it only watches for
changes in the `_worker.js` file, but not for changes in
any of its imported dependencies. This means that given
the following `_worker.js` file

```
import { graham } from "./graham-the-dog";
export default {
    fetch(request, env) {
	return new Response(graham)
    }
}
```

`pages dev` will reload for any changes in the `_worker.js`
file itself, but not for any changes in `graham-the-dog.js`,
which is its dependency.

Similarly, `pages dev` will not reload for any changes in
non-JS module imports, such as wasm/html/binary module
imports.

This commit addresses all the aforementioned issues.

Fixes #4824

* fixes

.changeset/poor-ads-poke.md

@@ -0,0 +1,22 @@
+---
+"wrangler": patch
+---
+
+fix: Fix `pages dev` watch mode [_worker.js]
+
+The watch mode in `pages dev` for Advanced Mode projects is currently partially broken, as it only watches for changes in the "\_worker.js" file, but not for changes in any of its imported dependencies. This means that given the following "\_worker.js" file
+
+```
+import { graham } from "./graham-the-dog";
+export default {
+	fetch(request, env) {
+		return new Response(graham)
+	}
+}
+```
+
+`pages dev` will reload for any changes in the `_worker.js` file itself, but not for any changes in `graham-the-dog.js`, which is its dependency.
+
+Similarly, `pages dev` will not reload for any changes in non-JS module imports, such as wasm/html/binary module imports.
+
+This commit fixes all the aforementioned issues.

packages/wrangler/e2e/pages-dev.test.ts

@@ -188,7 +188,7 @@ describe("pages dev", () => {
 
 		await setTimeout(5_000);
 
-		await worker.readUntil(/Failed to bundle/);
+		await worker.readUntil(/Failed to build/);
 
 		// And then make sure Wrangler hasn't crashed
 		await helper.seed({
@@ -234,7 +234,7 @@ describe("pages dev", () => {
 
 		await setTimeout(5_000);
 
-		await worker.readUntil(/Unexpected error building Functions directory/);
+		await worker.readUntil(/Failed to build Functions/);
 
 		// And then make sure Wrangler hasn't crashed
 		await helper.seed({
@@ -645,6 +645,78 @@ describe("pages dev", () => {
 			expect(hello).toMatchInlineSnapshot('"Updated Worker!"');
 		});
 
+		it("should support modifying dependencies during dev session (_worker)", async () => {
+			const helper = new WranglerE2ETestHelper();
+
+			await helper.seed({
+				"pets/bear.js": dedent`
+						export const bear = "BEAR!"
+						`,
+				"_worker.js": dedent`
+						import { bear } from "./pets/bear"
+						export default {
+							fetch(request, env) {
+								return new Response(bear)
+							}
+						}`,
+			});
+
+			const port = await getPort();
+			const worker = helper.runLongLived(`wrangler pages dev --port ${port} .`);
+			const { url } = await worker.waitForReady();
+
+			let bear = await fetchText(url);
+			expect(bear).toMatchInlineSnapshot('"BEAR!"');
+
+			await helper.seed({
+				"pets/bear.js": dedent`
+						export const bear = "We love BEAR!"
+						`,
+			});
+
+			await worker.waitForReload();
+
+			bear = await fetchText(url);
+			expect(bear).toMatchInlineSnapshot('"We love BEAR!"');
+		});
+
+		it("should support modifying external modules during dev session (_worker)", async () => {
+			const helper = new WranglerE2ETestHelper();
+
+			await helper.seed({
+				"graham.html": dedent`
+						<h1>Graham the dog</h1>
+						`,
+				"_worker.js": dedent`
+						import html from "./graham.html"
+						export default {
+							fetch(request, env) {
+								return new Response(html)
+							}
+						}`,
+			});
+
+			const port = await getPort();
+			const worker = helper.runLongLived(`wrangler pages dev --port ${port} .`);
+			const { url } = await worker.waitForReady();
+
+			let graham = await fetchText(url);
+			expect(graham).toMatchInlineSnapshot('"<h1>Graham the dog</h1>"');
+
+			await helper.seed({
+				"graham.html": dedent`
+						<h1>Graham is the bestest doggo</h1>
+						`,
+			});
+
+			await worker.waitForReload();
+
+			graham = await fetchText(url);
+			expect(graham).toMatchInlineSnapshot(
+				'"<h1>Graham is the bestest doggo</h1>"'
+			);
+		});
+
 		it("should support modifying _routes.json during dev session", async () => {
 			const helper = new WranglerE2ETestHelper();