closed flow also queues a closed todo on each agent that held one, after the clear

swarm-wire/src/notify_flows.rs

@@ -628,7 +628,10 @@ impl TodoSink {
 /// - `assigned`: a newly assigned agent gets a todo for the issue or PR.
 /// - `unassigned`: an agent taken off it gets that todo rewritten to say so.
 ///   Both write the same key, so the second replaces the first.
-/// - `closed`: closing it clears every router todo the router queued for it.
+/// - `closed`: closing it clears every router todo the router queued for it,
+///   then tells each agent that held one with a `closed` todo. The clear is the
+///   first child of the match and runs first: its prefix also covers the
+///   `closed` key.
 #[must_use]
 pub fn builtins() -> Vec<Flow> {
     let assignment_key = "forge:{repo}#{number}:assignment";
@@ -658,21 +661,41 @@ pub fn builtins() -> Vec<Flow> {
                     .to_owned(),
             },
         ),
-        chain(
-            "closed",
-            &["issues", "pull_request"],
-            "closed",
-            TodoSink {
-                to: Recipients::Field("todo_holders".to_owned()),
-                op: Op::Clear,
-                key: "forge:{repo}#{number}:".to_owned(),
-                prefix: true,
-                text: String::new(),
-            },
-        ),
+        closed(),
     ]
 }
 
+/// The `closed` flow: the clear, then the todo that says why.
+fn closed() -> Flow {
+    let mut flow = chain(
+        "closed",
+        &["issues", "pull_request"],
+        "closed",
+        TodoSink {
+            to: Recipients::Field("todo_holders".to_owned()),
+            op: Op::Clear,
+            key: "forge:{repo}#{number}:".to_owned(),
+            prefix: true,
+            text: String::new(),
+        },
+    );
+    flow.nodes.push(Node {
+        id: "inform".to_owned(),
+        kind: NodeKind::Todo(TodoSink {
+            to: Recipients::Field("todo_holders".to_owned()),
+            op: Op::Upsert,
+            key: "forge:{repo}#{number}:closed".to_owned(),
+            prefix: false,
+            text: "{kind} {repo}#{number} was closed: {title} ({url})".to_owned(),
+        }),
+    });
+    flow.edges.push(Edge {
+        from: "match".to_owned(),
+        to: "inform".to_owned(),
+    });
+    flow
+}
+
 /// source(`events`) → match(`action` = `action`) → `sink`.
 fn chain(id: &str, events: &[&str], action: &str, sink: TodoSink) -> Flow {
     let node = |id: &str, kind| Node {