Preserve behavior drafts until document commit succeeds

crates/oa-desktop/src/behavior/scenario.rs

@@ -103,7 +103,28 @@ struct Draft {
     values: BTreeMap<Id, String>,
 }
 impl State {
+    pub(super) fn pending_owner(&self) -> Option<Id> {
+        self.draft.as_ref().map(|d| d.owner)
+    }
+
+    pub(super) fn prepare_pending(&self, p: &Project) -> Result<Command, String> {
+        let command = self
+            .draft
+            .as_ref()
+            .ok_or("Choose a scenario tool first.")?
+            .command(p)?;
+        execute_batch(p, std::slice::from_ref(&command)).map_err(|e| e.to_string())?;
+        Ok(command)
+    }
+
+    pub(super) fn acknowledge_commit(&mut self) {
+        self.draft = None;
+    }
+
     pub fn update(&mut self, p: &Project, event: Event) -> Result<Option<Command>, String> {
+        if self.draft.is_some() && matches!(&event, Event::Start(..)) {
+            return Err(PENDING_DRAFT.into());
+        }
         match event {
             Event::Start(owner, tool) => {
                 if p.elements.get(&owner).map(oa_core::Element::kind) != Some(Kind::Scenario) {
@@ -127,14 +148,8 @@ impl State {
                     values: BTreeMap::new(),
                 });
             }
-            Event::Cancel => self.draft = None,
-            Event::Submit => {
-                let d = self.draft.as_ref().ok_or("Choose a scenario tool first.")?;
-                let command = d.command(p)?;
-                execute_batch(p, std::slice::from_ref(&command)).map_err(|e| e.to_string())?;
-                self.draft = None;
-                return Ok(Some(command));
-            }
+            Event::Cancel => self.acknowledge_commit(),
+            Event::Submit => return self.prepare_pending(p).map(Some),
             other => {
                 if let Some(d) = &mut self.draft {
                     match other {