[WIP] Error if a user tries to use durable objects with a service worker

.changeset/perfect-cycles-study.md

@@ -0,0 +1,7 @@
+---
+"wrangler": patch
+---
+
+Error if a user tries to implement durable objects with a service worker
+
+You can only implement Durable Objects in [Module Workers](https://developers.cloudflare.com/workers/learning/migrating-to-module-workers/#advantages-of-migrating), so we should error if we discover that a user is trying to implement a durable object alongside a Service Worker.

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

@@ -0,0 +1,171 @@
+import { writeFile } from "fs/promises";
+import path from "path";
+import guessWorkerFormat from "../entry";
+import { mockConsoleMethods } from "./helpers/mock-console";
+import { runInTempDir } from "./helpers/run-in-tmp";
+import { runWrangler } from "./helpers/run-wrangler";
+import writeWranglerToml from "./helpers/write-wrangler-toml";
+
+describe("entry", () => {
+  runInTempDir();
+  mockConsoleMethods();
+
+  it("should error when encountering a service worker with a durable object implementation", async () => {
+    await writeFile(
+      "./index.ts",
+      "addEventListener('fetch', () => \"hello, world!\")"
+    );
+    writeWranglerToml({
+      main: "index.ts",
+      durable_objects: {
+        bindings: [
+          {
+            name: "THIS_SHOULD_FAIL",
+            class_name: "ThisShouldFail",
+            script_name: "this-should-fail.js",
+          },
+        ],
+      },
+    });
+
+    await expect(runWrangler("publish")).rejects
+      .toThrowErrorMatchingInlineSnapshot(`
+            "You cannot implement a Durable Object in a Service Worker, and should migrate to the Module format instead.
+            https://developers.cloudflare.com/workers/learning/migrating-to-module-workers/"
+          `);
+  });
+
+  it("should error when encountering a service worker with a per-environment durable object implementation", async () => {
+    await writeFile(
+      "./index.ts",
+      "addEventListener('fetch', () => \"hello, world!\")"
+    );
+    writeWranglerToml({
+      main: "index.ts",
+      env: {
+        ENV_1: {
+          durable_objects: {
+            bindings: [
+              {
+                name: "THIS_SHOULD_FAIL",
+                class_name: "ThisShouldFail",
+                script_name: "this-should-fail.js",
+              },
+            ],
+          },
+        },
+      },
+    });
+
+    await expect(runWrangler("publish")).rejects
+      .toThrowErrorMatchingInlineSnapshot(`
+            "You cannot implement a Durable Object in a Service Worker, and should migrate to the Module format instead.
+            https://developers.cloudflare.com/workers/learning/migrating-to-module-workers/"
+          `);
+  });
+
+  it("should allow service workers to bind to durable objects defined elsewhere", async () => {
+    await writeFile(
+      "./index.ts",
+      "addEventListener('fetch', () => \"hello, world!\")"
+    );
+    writeWranglerToml({
+      main: "index.ts",
+      durable_objects: {
+        bindings: [
+          {
+            name: "THIS_SHOULD_PASS",
+            class_name: "ThisShouldPass",
+          },
+        ],
+      },
+    });
+
+    await expect(
+      runWrangler("publish")
+    ).rejects.toThrowErrorMatchingInlineSnapshot(
+      `"Did not login, quitting..."`
+    );
+  });
+
+  it("should allow service workers to bind to per-environment durable objects defined elsewhere", async () => {
+    await writeFile(
+      "./index.ts",
+      "addEventListener('fetch', () => \"hello, world!\")"
+    );
+    writeWranglerToml({
+      main: "index.ts",
+      env: {
+        ENV_1: {
+          durable_objects: {
+            bindings: [
+              {
+                name: "THIS_SHOULD_PASS",
+                class_name: "ThisShouldPass",
+              },
+            ],
+          },
+        },
+      },
+    });
+
+    await expect(
+      runWrangler("publish")
+    ).rejects.toThrowErrorMatchingInlineSnapshot(
+      `"Did not login, quitting..."`
+    );
+  });
+
+  describe("guess worker format", () => {
+    it('should detect a "modules" worker', async () => {
+      await writeFile("./index.ts", "export default {};");
+      // Note that this isn't actually a valid worker, because it's missing
+      // a fetch handler. Regardless, our heuristic is simply to check for exports.
+      const guess = await guessWorkerFormat(
+        path.join(process.cwd(), "./index.ts"),
+        process.cwd(),
+        undefined
+      );
+      expect(guess).toBe("modules");
+    });
+
+    it('should detect a "service-worker" worker', async () => {
+      await writeFile("./index.ts", "");
+      // Note that this isn't actually a valid worker, because it's missing
+      // a fetch listener. Regardless, our heuristic is simply to check for
+      // the lack of exports.
+      const guess = await guessWorkerFormat(
+        path.join(process.cwd(), "./index.ts"),
+        process.cwd(),
+        undefined
+      );
+      expect(guess).toBe("service-worker");
+    });
+
+    it("should throw an error when the hint doesn't match the guess (modules - service-worker)", async () => {
+      await writeFile("./index.ts", "export default {};");
+      await expect(
+        guessWorkerFormat(
+          path.join(process.cwd(), "./index.ts"),
+          process.cwd(),
+          "service-worker"
+        )
+      ).rejects.toThrow(
+        "You configured this worker to be a 'service-worker', but the file you are trying to build appears to have ES module exports. Please pass `--format modules`, or simply remove the configuration."
+      );
+    });
+
+    it("should throw an error when the hint doesn't match the guess (service-worker - modules)", async () => {
+      await writeFile("./index.ts", "");
+      await expect(
+        guessWorkerFormat(
+          path.join(process.cwd(), "./index.ts"),
+          process.cwd(),
+          "modules"
+        )
+      ).rejects.toThrow(
+        "You configured this worker to be 'modules', but the file you are trying to build doesn't export a handler. Please pass `--format service-worker`, or simply remove the configuration."
+      );
+    });
+  });
+});

packages/wrangler/src/entry.ts

@@ -48,6 +48,13 @@ export async function getEntry(
     directory,
     args.format ?? config.build?.upload?.format
   );
+
+  if (format === "service-worker" && hasDurableObjectImplementation(config)) {
+    throw new Error(
+      "You cannot implement a Durable Object in a Service Worker, and should migrate to the Module format instead.\nhttps://developers.cloudflare.com/workers/learning/migrating-to-module-workers/"
+    );
+  }
+
   return { file, directory, format };
 }
 
@@ -157,3 +164,19 @@ export function fileExists(filePath: string): boolean {
   }
   return false;
 }
+
+/**
+ * Returns true if the given config contains durable object bindings
+ */
+function hasDurableObjectImplementation(config: Config): boolean {
+  const topLevel = config.durable_objects.bindings.some(
+    (binding) => binding.script_name !== undefined
+  );
+  const nested = Object.values(config.env).some((env) =>
+    env.durable_objects.bindings.some(
+      (binding) => binding.script_name !== undefined
+    )
+  );
+
+  return topLevel || nested;
+}