value cache: keep track of expired values in case of edition

src/value_cache.h

@@ -165,6 +165,7 @@ private:
     CallbackQueue addValues(const std::vector<Sp<Value>>& new_values, const TypeStore& types, const time_point& now)
     {
         std::vector<Sp<Value>> nvals;
+        std::vector<Sp<Value>> expired_vals;
         for (const auto& value : new_values) {
             auto v = values.find(value->id);
             if (v == values.end()) {
@@ -175,9 +176,18 @@ private:
                 // refreshed value
                 v->second.created = now;
                 v->second.expiration = now + types.getType(v->second.data->type).expiration;
+                if (*v->second.data != *value) {
+                    expired_vals.emplace_back(v->second.data);
+                    v->second.data = value;
+                    nvals.emplace_back(value);
+                }
             }
         }
         CallbackQueue ret;
+        if (callback and not expired_vals.empty())
+            ret.emplace_back([cb = callback, expired_vals = std::move(expired_vals)]{
+                cb(expired_vals, true);
+            });
         if (callback and not nvals.empty())
             ret.emplace_back([cb = callback, nvals = std::move(nvals)] { cb(nvals, false); });
         return ret;