Add mount check to Durable Object missing script error, closes #221

Author: mrbbot

packages/durable-objects/src/plugin.ts

@@ -249,7 +249,8 @@ export class DurableObjectsPlugin
         if (!scriptExports) {
           throw new DurableObjectError(
             "ERR_SCRIPT_NOT_FOUND",
-            `Script "${scriptName}" for Durable Object "${name}" not found`
+            `Script "${scriptName}" for Durable Object "${name}" not found.
+Make sure "${scriptName}" is mounted so Miniflare knows where to find it.`
           );
         }
         constructor = scriptExports[className];

packages/durable-objects/test/plugin.spec.ts

@@ -288,7 +288,9 @@ test("DurableObjectPlugin: reload: throws if script cannot be found in mounts",
   t.throws(() => plugin.reload({}, {}, new Map()), {
     instanceOf: DurableObjectError,
     code: "ERR_SCRIPT_NOT_FOUND",
-    message: 'Script "test" for Durable Object "TEST" not found',
+    message:
+      'Script "test" for Durable Object "TEST" not found.\n' +
+      'Make sure "test" is mounted so Miniflare knows where to find it.',
   });
 });
 test("DurableObjectsPlugin: reload: throws if object constructor cannot be found in mount exports", (t) => {