test(incremental): hidden members under every aggregation, evidence and the step 4 reasoning (improvise-u2le)

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01VdfEGXA7aJ6ftMsCc9PJze

crates/improvise-incremental/tests/incremental.rs

@@ -9,8 +9,8 @@ use improvise_core::model::cell::CellValue;
 use improvise_core::view::View;
 use improvise_incremental::{Edit, Incremental, differential_in};
 use support::{
-    corpus, edits_for, grouped_model, hand_model, hidden_workbook, none_of, ratio_workbook,
-    wide_workbook,
+    corpus, edits_for, grouped_model, hand_model, hidden_counted_workbook, hidden_workbook,
+    none_of, ratio_workbook, wide_workbook,
 };
 
 fn run(model: &Model, views: &[View], none: &[String], edits: &[Edit]) -> Result<(), String> {
@@ -77,6 +77,27 @@ fn incremental_matches_eager_on_hidden_items_and_collapsed_groups() {
     run(&wb.model, &views, &none, &edits).unwrap();
 }
 
+#[test]
+fn incremental_matches_eager_on_a_collapsed_group_with_a_hidden_member_under_every_aggregation() {
+    let wb = hidden_counted_workbook();
+    let views: Vec<View> = wb.views.values().cloned().collect();
+    let none = none_of(&wb);
+    let mut edits = agg_edits("Revenue");
+    edits.push(Edit::SetCell(
+        support::key("Inland", "A", "Revenue"),
+        CellValue::Number(f64::NAN),
+    ));
+    edits.extend(agg_edits("Revenue"));
+    run(&wb.model, &views, &none, &edits).unwrap();
+}
+
+#[test]
+fn incremental_matches_eager_on_a_formula_read_under_every_aggregation() {
+    let model = hand_model();
+    let none = vec!["Region".to_string()];
+    run(&model, &[], &none, &agg_edits("Profit")).unwrap();
+}
+
 #[test]
 fn incremental_matches_eager_on_a_group_read_without_a_view() {
     let model = grouped_model();

crates/improvise-incremental/tests/measure.rs

@@ -181,3 +181,18 @@ fn occupancy_with_a_hidden_item_reads_the_groups_it_subtracts() {
         "the line, less p3 under it"
     );
 }
+
+#[test]
+fn a_group_whose_cells_are_all_cleared_is_no_longer_read() {
+    let mut backend = Incremental::new(table(2, AggFunc::Count), vec![]);
+    let one = cell(1, 1, 1);
+    assert_eq!(backend.raw_fold(&one), Some(CellValue::Number(1.0)));
+    backend.apply(&Edit::ClearCell(cell(1, 1, 1)));
+    let before = backend.meter();
+    assert_eq!(backend.raw_fold(&one), None, "nothing is left under it");
+    assert_eq!(
+        since(before, backend.meter()).reads,
+        0,
+        "and no empty group stands in for it"
+    );
+}

crates/improvise-incremental/tests/support/mod.rs

@@ -223,3 +223,13 @@ pub fn ratio_workbook() -> improvise_core::workbook::Workbook {
     view.set_axis("Product", Axis::None);
     wb
 }
+
+/// [`hidden_workbook`] drawn with the measure on the columns and Product folded: its cells
+/// carry a measure, so the measure's aggregation reaches every row, total and collapsed group.
+pub fn hidden_counted_workbook() -> improvise_core::workbook::Workbook {
+    let mut wb = hidden_workbook();
+    let view = wb.active_view_mut();
+    view.set_axis("Product", Axis::None);
+    view.set_axis("_Measure", Axis::Column);
+    wb
+}