fix(code-runtime): preserve typed failures after mutation

packages/code-runtime/code-runtime-worker/src/bootstrap.ts

@@ -10,6 +10,17 @@ import type { DoneMessage, ReplyMessage, WorkerBootData, WorkerToHost } from './
 import { jsonStringBytesUpTo, jsonValueBytesUpTo, truncateJsonStringBytes } from './output-json.ts'
 import { decodeWorkerJson, encodeWorkerJson, snapshotCodeJsonValue } from './worker-json.ts'
 
+const capturedObjectCreate = Object.create
+const capturedObjectDefineProperty = Object.defineProperty
+
+/** Define one public binding-error field without consulting mutable globals or descriptor prototypes. */
+function defineBindingErrorField(error: Error, key: string, value: string): void {
+  const attributes = capturedObjectCreate(null) as PropertyDescriptor
+  attributes.enumerable = true
+  attributes.value = value
+  capturedObjectDefineProperty(error, key, attributes)
+}
+
 /** The port surface the bootstrap needs — satisfied by `parentPort` and by the tests' fake. */
 export interface BootstrapPort {
   postMessage(message: WorkerToHost): void
@@ -236,8 +247,8 @@ function makeBindingErrorClass(
   return class BindingCallError extends Error {
     constructor(memberName: string, message: string) {
       super(message)
-      Object.defineProperty(this, 'name', { enumerable: true, value: descriptor.name })
+      defineBindingErrorField(this, 'name', descriptor.name)
-      Object.defineProperty(this, descriptor.memberNameProperty, { enumerable: true, value: memberName })
+      defineBindingErrorField(this, descriptor.memberNameProperty, memberName)
     }
   }
 }

packages/code-runtime/code-runtime-worker/tests/runtime.spec.ts

@@ -681,14 +681,19 @@ describe('WorkerCodeRuntime — hostile programs (real workers)', () => {
         objectPrototype.constructor = arrayPrototype.constructor = null;
         globalThis.Array = globalThis.Buffer = globalThis.Function = globalThis.Number = globalThis.Object = globalThis.Reflect = globalThis.Set = globalThis.String = undefined;
         const echoed = await tools.echo({ request: ['€', 1] });
-        return { echoed, completion: { ok: true, amount: 42 } };
+        let failure;
+        try { await tools.fail({}) } catch (error) {
+          failure = { typed: error instanceof ToolCallError, name: error.name, toolName: error.toolName, message: error.message };
+        }
+        return { echoed, failure, completion: { ok: true, amount: 42 } };
       `,
-      bindings: tools({ echo: async args => args }),
+      bindings: tools({ echo: async args => args, fail: async () => { throw new Error('nope') } }),
     })
     expect(result).toEqual({
       logs: [],
       value: {
         echoed: { request: ['€', 1] },
+        failure: { typed: true, name: 'ToolCallError', toolName: 'fail', message: 'nope' },
         completion: { ok: true, amount: 42 },
       },
     })