Document that DurableObjectId::name is passed through to the object

test/src/durable.rs

@@ -16,13 +16,16 @@ use worker::{
 pub struct MyClass {
     state: State,
     number: AssertUnwindSafe<Cell<usize>>,
+    ctor_name: Option<String>,
 }
 
 impl DurableObject for MyClass {
     fn new(state: State, _env: Env) -> Self {
+        let ctor_name = state.id().name();
         Self {
             state,
             number: AssertUnwindSafe(Cell::new(0)),
+            ctor_name,
         }
     }
 
@@ -38,6 +41,15 @@ impl DurableObject for MyClass {
                         .unwrap_or_else(|| "unknown".to_string());
                     Response::ok(format!("Hello from {name}!"))
                 }
+                "/ctor-name" => {
+                    // Return the name captured in the constructor, verifying it
+                    // is available before any request is handled.
+                    let name = self
+                        .ctor_name
+                        .clone()
+                        .unwrap_or_else(|| "unknown".to_string());
+                    Response::ok(format!("Hello from {name}!"))
+                }
                 "/storage" => {
                     let storage = self.state.storage();
                     let map = [("one".to_string(), 1), ("two".to_string(), 2)]
@@ -212,6 +224,19 @@ pub async fn handle_hello(
     stub.fetch_with_str("https://fake-host/hello").await
 }
 
+#[worker::send]
+pub async fn handle_ctor_name(
+    _req: Request,
+    env: Env,
+    _data: crate::SomeSharedData,
+) -> Result<Response> {
+    let namespace = env.durable_object("MY_CLASS")?;
+    let name = "my-durable-object";
+    let id = namespace.id_from_name(name)?;
+    let stub = id.get_stub()?;
+    stub.fetch_with_str("https://fake-host/ctor-name").await
+}
+
 #[worker::send]
 pub async fn handle_hello_unique(
     _req: Request,

test/src/router.rs

@@ -220,6 +220,7 @@ macro_rules! add_routes (
     add_route!($obj, get, "/socket/read",  socket::handle_socket_read);
     add_route!($obj, get, "/durable/auto-response", auto_response::handle_auto_response);
     add_route!($obj, get, "/durable/hello", durable::handle_hello);
+    add_route!($obj, get, "/durable/ctor-name", durable::handle_ctor_name);
     add_route!($obj, get, "/durable/hello-unique", durable::handle_hello_unique);
     add_route!($obj, get, "/durable/storage", durable::handle_storage);
     add_route!($obj, get, "/durable/handle-basic-test", durable::handle_basic_test);

test/tests/durable.spec.ts

@@ -65,6 +65,15 @@ describe("durable", () => {
     expect(text).toBe("Hello from my-durable-object!");
   });
 
+  // The name should be available in the constructor, before any request is
+  // handled (see https://github.com/cloudflare/workerd/issues/2240).
+  test("id-from-name preserves name on state.id() in constructor", async () => {
+    const resp = await mf.dispatchFetch(`${mfUrl}durable/ctor-name`);
+    expect(resp.status).toBe(200);
+    const text = await resp.text();
+    expect(text).toBe("Hello from my-durable-object!");
+  });
+
   // unique_id() DOs should not have a name on state.id().
   test("unique-id has no name on state.id()", async () => {
     const resp = await mf.dispatchFetch(`${mfUrl}durable/hello-unique`);

worker/src/durable.rs

@@ -205,8 +205,16 @@ impl ObjectId<'_> {
     }
 
     /// The name that was used to create the `ObjectId` via [`id_from_name`](https://developers.cloudflare.com/durable-objects/api/namespace/#idfromname).
-    /// `None` is returned if the `ObjectId` was constructed using [`unique_id`](https://developers.cloudflare.com/durable-objects/api/namespace/#newuniqueid).
-    /// `None` is also returned within the Durable Object constructor, as the `name` property is not accessible there (see <https://github.com/cloudflare/workerd/issues/2240>).
+    ///
+    /// When a Durable Object is addressed by name, the name is also passed
+    /// through to the object itself and is available via `state.id().name()`,
+    /// including inside the constructor and [`alarm`](crate::DurableObject::alarm)
+    /// handlers (see <https://github.com/cloudflare/workerd/issues/2240>).
+    ///
+    /// `None` is returned in some cases, for example when the `ObjectId` was
+    /// constructed via [`unique_id`](https://developers.cloudflare.com/durable-objects/api/namespace/#newuniqueid).
+    /// See the [Durable Object ID docs](https://developers.cloudflare.com/durable-objects/api/id/#name)
+    /// for the full list of cases.
     pub fn name(&self) -> Option<String> {
         self.inner.name()
     }