Remove connections for a node that is being deleted. (#7185)

Fixes https://github.com/enso-org/enso/issues/7135

https://github.com/enso-org/enso/assets/1428930/85433a69-03dc-4ad9-9563-717a78ff6ff8

app/gui/src/controller/graph.rs

@@ -283,6 +283,16 @@ impl Connections {
             target: Self::convert_endpoint(&connection.target),
         }
     }
+
+    /// Return all connections that involve the given node.
+    pub fn with_node(&self, node: node::Id) -> impl Iterator<Item = Connection> {
+        self.connections
+            .iter()
+            .filter(move |conn| conn.source.node == node || conn.target.node == node)
+            .copied()
+            .collect_vec()
+            .into_iter()
+    }
 }
 
 

app/gui/src/controller/graph/executed.rs

@@ -451,6 +451,21 @@ impl Handle {
         }
     }
 
+    /// Remove all the connections from the graph. This is a convenience method that calls
+    /// [`disconnect`] for each connection. If any of the calls fails, the first error is
+    /// propagated, but all the connections are attempted to be disconnected.
+    pub fn disconnect_all(&self, connections: impl Iterator<Item = Connection>) -> FallibleResult {
+        let errors =
+            connections.map(|c| self.disconnect(&c)).filter_map(|r| r.err()).collect::<Vec<_>>();
+        // Failure has no good way to propagate multiple errors with `Failure`. So we propagate
+        // only the first one.
+        if let Some(error) = errors.into_iter().next() {
+            Err(error)
+        } else {
+            Ok(())
+        }
+    }
+
     /// Set the execution environment.
     pub async fn set_execution_environment(
         &self,

app/gui/src/presenter/graph.rs

@@ -292,6 +292,17 @@ impl Model {
             || {
                 let ast_id = self.state.update_from_view().remove_node(id)?;
                 self.widget.remove_all_node_widgets(ast_id);
+
+                let connections = self.controller.connections();
+                let node_connections = connections.map(|c| c.with_node(ast_id));
+                let disconnect_result = node_connections.map(|c| self.controller.disconnect_all(c));
+                if let Err(e) = disconnect_result {
+                    warn!(
+                        "Failed to disconnect all connections from node {:?} because of {:?}",
+                        ast_id, e
+                    );
+                }
+
                 Some(self.controller.graph().remove_node(ast_id))
             },
             "remove node",