broker: remove op deletes an actor (on top of tap/untap)

{"type":"remove","actor"} shuts the actor down normally, drops its
mailbox, supervisor and actor.json entry (so also its subscriptions and
tap), and deletes /actor/<id>/. Native actors cannot be removed.
Re-applied from card-1-broker-remove (3c91747) onto card-2-broker-tap.

cli/src/broker.rs

@@ -1,7 +1,7 @@
 //! The broker: message routing, mailboxes, subscriptions, taps, the version
 //! store, and the requests to `broker` (spawn, upgrade, rollback, stop, start,
-//! subscribe, unsubscribe, tap, untap, scan, exit). `supervisor.rs` runs each
-//! WASM actor.
+//! remove, subscribe, unsubscribe, tap, untap, scan, exit). `supervisor.rs`
+//! runs each WASM actor.
 //!
 //! The broker accepts only `.wasm` files. It does not know any source language.
 //! The world folder is the source of truth: `scan` boots every
@@ -377,6 +377,35 @@ impl Broker {
         Ok(result)
     }
 
+    /// Stop an actor (normal shutdown) and delete its folder `actor/<id>/`.
+    /// Afterwards the ID is unknown: messages to it are undeliverable, and
+    /// it can be spawned again from scratch.
+    pub async fn remove_actor(&self, id: &str) -> Result<Value> {
+        if NATIVE.contains(&id) {
+            bail!("{id} is part of the host and cannot be removed");
+        }
+        if !world::valid_id(id) {
+            bail!("invalid actor ID {id:?}");
+        }
+        let lock = self.op_lock(id);
+        let _guard = lock.lock().await;
+        let dir = self.world.actor_dir(id);
+        if !self.is_supervised(id) && !dir.is_dir() {
+            bail!("no actor with ID {id}");
+        }
+        if self.is_supervised(id) {
+            self.control(id, |reply| Control::Shutdown { reply }).await?;
+        }
+        // Without its mailbox, messages to `id` are undeliverable.
+        self.controls.lock().unwrap().remove(id);
+        self.mailboxes.lock().unwrap().remove(id);
+        self.metas.lock().unwrap().remove(id);
+        if dir.exists() {
+            std::fs::remove_dir_all(&dir).with_context(|| format!("delete {}", dir.display()))?;
+        }
+        Ok(json!({"type": "removed", "actor": id}))
+    }
+
     /// Boot the actors in `actor/`. Called at start and on `scan`.
     ///
     /// - An `actor.wasm` equal to the installed version starts as is.
@@ -481,6 +510,7 @@ impl Broker {
             }
             "stop" => self.control(&actor()?, |reply| Control::Stop { reply }).await,
             "start" => self.control(&actor()?, |reply| Control::Start { reply }).await,
+            "remove" => self.remove_actor(&actor()?).await,
             "subscribe" | "unsubscribe" => {
                 let publisher = actor()?;
                 let on = ty == "subscribe";
@@ -506,7 +536,7 @@ impl Broker {
                 self.exit.notify_one();
                 Ok(json!({"type": "exiting"}))
             }
-            other => bail!("unknown broker request {other:?}. Known: spawn, upgrade, rollback, stop, start, subscribe, unsubscribe, tap, untap, scan, exit"),
+            other => bail!("unknown broker request {other:?}. Known: spawn, upgrade, rollback, stop, start, remove, subscribe, unsubscribe, tap, untap, scan, exit"),
         }
     }
 

cli/tests/host.rs

@@ -494,6 +494,62 @@ async fn explicit_rollback_keeps_current_data() {
     host.stop().await;
 }
 
+#[tokio::test]
+async fn remove_shuts_an_actor_down_and_deletes_its_folder() {
+    let world = create_world("remove");
+    let wasm = toolbox_wasm().clone();
+    let (host, mut mailbox) = start(&world).await;
+    let source = passing_source(&world, "source");
+    spawn_type(&host, &mut mailbox, "doomed", &wasm, &source).await;
+    let write = json!({"type": "write", "path": "/data/state", "text": "x"});
+    ask_type(&host, &mut mailbox, "doomed", write, "ok").await;
+    ask_type(&host, &mut mailbox, "doomed", json!({"type": "arm-shutdown"}), "armed").await;
+
+    // Normal shutdown: the actor gets "shutdown" and its last message is routed.
+    let id = host.broker.send("console", Some("broker"), None, None, json!({"type": "remove", "actor": "doomed"}));
+    let (mut removed, mut last_words) = (false, false);
+    tokio::time::timeout(Duration::from_secs(10), async {
+        while !removed || !last_words {
+            let message = mailbox.recv().await.expect("console mailbox closed");
+            if message.reply_to.as_deref() == Some(id.as_str()) {
+                assert_eq!(message.body, json!({"type": "removed", "actor": "doomed"}));
+                removed = true;
+            } else if message.reply_to.as_deref() == Some("broker/shutdown") {
+                assert_eq!(message.body["type"], "shutdown-reply");
+                last_words = true;
+            }
+        }
+    })
+    .await
+    .expect("remove did not answer or did not shut the actor down");
+    assert!(!world.actor_dir("doomed").exists());
+
+    let gone = ask(&host, &mut mailbox, "doomed", json!({"type": "echo", "value": "hi"})).await;
+    assert_eq!(gone.body["type"], "undeliverable");
+    let again = request(&host, &mut mailbox, json!({"type": "remove", "actor": "doomed"})).await;
+    assert_eq!(again.body["type"], "error");
+    let broker = request(&host, &mut mailbox, json!({"type": "remove", "actor": "broker"})).await;
+    assert_eq!(broker.body["type"], "error");
+    assert!(world.actor_dir("broker").exists());
+
+    // The ID is free again: a new spawn starts at version 1 with empty data.
+    assert_eq!(spawn_type(&host, &mut mailbox, "doomed", &wasm, &source).await.body["version"], 1);
+    let read = json!({"type": "read", "path": "/data/state"});
+    ask_type(&host, &mut mailbox, "doomed", read, "error").await;
+    host.stop().await;
+}
+
+#[tokio::test]
+async fn unknown_broker_request_lists_the_known_ones() {
+    let world = create_world("unknown-request");
+    let (host, mut mailbox) = start(&world).await;
+    let unknown = request(&host, &mut mailbox, json!({"type": "frobnicate"})).await;
+    assert_eq!(unknown.body["type"], "error");
+    let reason = unknown.body["reason"].as_str().unwrap();
+    assert!(reason.contains("remove") && reason.contains("tap"), "{reason}");
+    host.stop().await;
+}
+
 #[tokio::test]
 async fn cargo_actor_builds_valid_crates_and_reports_compiler_errors() {
     let world = create_world("cargo-actor");