code to test cloudflare/workerd#2131

index.js

@@ -1,8 +1,28 @@
 import { Miniflare } from "miniflare";
 
 const modules = {
-  "/hello.js": {
-    esModule: 'export const hello = "Hello";',
+  "/foo/hello.js": {
+    esModule: `
+    import {foo} from "./foo.js";
+
+    export const hello = "Hello" + foo;`,
+  },
+  "/foo/foo.js": {
+    esModule: `
+    import {bar} from "bar";
+
+    export const foo = " foo" + bar`,
+  },
+  // TODO: shouldn't this be "/_bare_/bar", or even "bar/", or ideally just "bar"?
+  "/_bare_/bar/index": {
+    esModule: `
+    import {baz} from "./baz.js";
+
+    export const bar = " bar" + baz`,
+  },
+  "/_bare_/bar/baz.js": {
+    esModule: `
+    export const baz = " baz"`,
   },
 };
 
@@ -15,17 +35,51 @@ const mf = new Miniflare({
 
     const url = new URL(request.url);
     const specifier = url.searchParams.get("specifier");
-    if (!specifier) {
+    const referrer = url.searchParams.get("referrer")
+    const rawSpecifier = url.searchParams.get("raw");
+
+    if (!rawSpecifier) {
       throw new Error("no specifier provided");
     }
 
-    if (!modules[specifier]) {
+    // hacky way to resolve url paths - this is good enough for this demo, but likely not good enough for production use
+    const resolvedSpecifier = rawSpecifier.startsWith('.') ?
+      new URL(rawSpecifier, `https://hostname${referrer}`).pathname :
+      rawSpecifier.startsWith('/') ?
+        // TODO(discuss): what does it mean to import '/foo.js' vs 'foo.js' vs './foo.js' in workerd?!?
+        rawSpecifier :
+        // TODO(discuss): workerd crashes if we 301 redirect with bare specifier,
+        //    so prefix with /_bare_/ - this is likely a bad idea!
+        rawSpecifier.endsWith('.js') ?
+          `/_bare_/${rawSpecifier}`:
+          // TODO(discuss): workerd crashes if we 301 redirect to location that ends with /,
+          //    so we have to use /index suffix instead
+          `/_bare_/${rawSpecifier}/index`;
+
+    console.log(`--- Fallback service debug info ---
+      resolve method:     ${resolveMethod}
+      url:                ${url}
+      specifier:          ${specifier}
+      raw specifier:      ${rawSpecifier}
+      referrer:           ${referrer}
+      resolved specifier: ${resolvedSpecifier}`
+    );
+
+    if (specifier !== resolvedSpecifier) {
+      console.log(`redirecting module ${specifier} to ${resolvedSpecifier}`);
+      return new Response(null, {headers: {location: resolvedSpecifier}, status: 301});
+    }
+
+
+    const resolvedModule = modules[resolvedSpecifier];
+
+    if (!resolvedModule) {
       return new Response(null, { status: 404 });
     }
 
     return new Response(
       JSON.stringify({
-        ...modules[specifier],
+        ...resolvedModule,
       })
     );
   },
@@ -41,7 +95,7 @@ const mf = new Miniflare({
           contents: `
             export default {
               async fetch() {
-                const { hello } = await import("./hello.js");
+                const { hello } = await import("./foo/hello.js");
                 return new Response(hello + " World");
               }
             }