Refuse DeleteView of an absent view and AddFormula into an absent category (improvise-40j4)

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01VdfEGXA7aJ6ftMsCc9PJze

crates/improvise-command/src/ui/effect.rs

@@ -208,11 +208,13 @@ impl Effect for AddFormula {
                 // grid; _Measure targets arrive via `measure_item_names()`.
                 if !crate::model::category::CategoryKind::of_name(&formula.target_category)
                     .is_measure()
+                && let Err(e) = app
+                    .model_state
+                    .workbook
+                    .add_item(&formula.target_category, &formula.target)
                 {
-                    let _ = app
-                        .model_state
-                        .workbook
-                        .add_item(&formula.target_category, &formula.target);
+                    // Its category may be gone: store no formula for it (40j4).
+                    return refused(app, e.to_string());
                 }
                 app.model_state.workbook.model.add_formula(formula);
             }
@@ -341,6 +343,11 @@ impl Effect for CreateView {
 pub struct DeleteView(pub String);
 impl Effect for DeleteView {
     fn apply(&self, app: &mut App) {
+        // `delete_view` answers Ok for a name it lacks, which is a failure to
+        // report, not a deletion (improvise-40j4).
+        if !app.model_state.workbook.views.contains_key(&self.0) {
+            return refused(app, format!("No view named \"{}\"", self.0));
+        }
         if let Err(e) = app.model_state.workbook.delete_view(&self.0) {
             return refused(app, e.to_string());
         }

crates/improvise-command/src/ui/host.rs

@@ -1907,6 +1907,38 @@ mod tests {
         );
     }
 
+    /// improvise-40j4: the formula was stored for a category the frame's own
+    /// first command removed, and it survived save and reload.
+    #[test]
+    fn a_frame_adding_a_formula_to_a_category_its_first_command_removed_is_refused() {
+        let mut host = host();
+        let (asker, _) = host.connect(10, 10);
+
+        let answer = host.handle(
+            asker,
+            two_command_frame(
+                &host,
+                ModelCommand::RemoveCategory("Region".into()),
+                ModelCommand::AddFormula {
+                    raw: "Total = 1".into(),
+                    target_category: "Region".into(),
+                },
+            ),
+        );
+
+        assert_eq!(
+            to(&answer, asker),
+            vec![ServerFrame::Rejected(Rejection::MutationRefused)],
+            "a formula for a vanished category was accepted: {answer:?}"
+        );
+        let model = &host.app().model_state.workbook.model;
+        assert!(model.category("Region").is_some(), "the removal must be undone");
+        assert!(
+            model.formulas().iter().all(|f| f.target != "Total"),
+            "and the formula must not be stored"
+        );
+    }
+
     /// A host whose storage holds one file per way `ImportJsonHeadless` can
     /// fail, plus nothing at the two paths that must fail to read.
     fn host_with_import_fixtures() -> Host {
@@ -1923,7 +1955,10 @@ mod tests {
             crate::storage::Storage::write(&storage, Path::new(name), bytes)
                 .expect("fixture writes");
         }
-        let mut app = App::new(workbook(), None);
+        // A second view, so deleting an absent one is not refused as "the last".
+        let mut wb = workbook();
+        wb.create_view("Scratch");
+        let mut app = App::new(wb, None);
         app.storage = Box::new(storage);
         app.rebuild_layout();
         Host::new(app)
@@ -1963,6 +1998,15 @@ mod tests {
             ("ImportJsonHeadless of JSON that does not parse", import("bad.json", None)),
             ("ImportJsonHeadless at a path with no array", import("nested.json", Some("nope"))),
             ("ImportJsonHeadless that builds no model", import("measures.json", None)),
+            // improvise-40j4: `delete_view` answers Ok for a name it lacks.
+            ("DeleteView of a view the document lacks", ModelCommand::DeleteView("Ghost".into())),
+            (
+                "AddFormula into a category the document lacks",
+                ModelCommand::AddFormula {
+                    raw: "Total = 1".into(),
+                    target_category: "Ghost".into(),
+                },
+            ),
         ];
         for (what, failing) in cases {
             let mut host = host_with_import_fixtures();