0 is out of stock and nothing is available from now on

src/controllers/cart.rs

@@ -97,9 +97,9 @@ async fn add(
     let mut items = parse_cart(&jar);
     let add_qty = form.quantity.unwrap_or(1).max(1);
     if let Some(entry) = items.iter_mut().find(|(id, _)| *id == variant.id) {
-        entry.1 = (entry.1 + add_qty).min(variant.stock);
+        entry.1 = variant.cap(entry.1 + add_qty);
     } else {
-        items.push((variant.id, add_qty.min(variant.stock)));
+        items.push((variant.id, variant.cap(add_qty)));
     }
     items.retain(|(_, qty)| *qty > 0);
 
@@ -128,13 +128,14 @@ async fn update(
     headers: HeaderMap,
     Form(form): Form<UpdateForm>,
 ) -> Result<Response> {
-    let stock = published_variant(&ctx, form.variant_id)
-        .await?
-        .map(|(v, _)| v.stock)
-        .unwrap_or(0);
+    // Clamp the requested quantity to what's available (no cap for untracked
+    // variants); a removed variant clamps to 0 and drops out below.
+    let clamped = match published_variant(&ctx, form.variant_id).await? {
+        Some((variant, _)) => variant.cap(form.quantity),
+        None => 0,
+    };
 
     let mut items = parse_cart(&jar);
-    let clamped = form.quantity.clamp(0, stock);
     if let Some(entry) = items.iter_mut().find(|(id, _)| *id == form.variant_id) {
         entry.1 = clamped;
     }
@@ -208,7 +209,7 @@ pub(crate) async fn resolve_cart(
         let Some((variant, product)) = published_variant(ctx, id).await? else {
             continue;
         };
-        let qty = qty.clamp(0, variant.stock);
+        let qty = variant.cap(qty);
         if qty == 0 {
             continue;
         }