mw::com: Update slot count based on the presence of Notifer Tag in Field.

score/mw/com/design/events_fields/README.md

@@ -76,6 +76,23 @@ The same asymmetry shows up in how each side builds the field's event dispatch:
 - On the proxy side, the event dispatch (`proxy_event_dispatch_`) is only created when `WithNotifier` is set. Without it
   the member stays `nullptr` and the notifier methods are removed at compile time.
 
+The notifier also decides how many sample slots the provider allocates. `numberOfSampleSlots` exists to give
+subscribers something to read: the provider sizes the slot pool so all consumers can hold their samples while it
+keeps publishing (see the formula in the [configuration readme](../../impl/configuration/README.md)). Without
+`WithNotifier` no consumer can ever subscribe (proxy and skeleton are compiled from the same tag pack), so there is
+nothing to size. The skeleton only needs two slots for its own `Update()`: one holds the current value, one is
+written by the next update. The LoLa binding therefore ignores the configured value for such fields:
+
+| `WithNotifier` | `numberOfSampleSlots` | used slot count            |
+| -------------- | --------------------- | -------------------------- |
+| enabled        | configured            | as configured              |
+| enabled        | missing               | none, startup terminates   |
+| disabled       | missing               | 2                          |
+| disabled       | configured            | 2, a warning is logged     |
+
+Configured `numberOfIpcTracingSlots` come on top of the used slot count in all cases, because tracing holds a
+reference to each traced sample until the trace call has completed.
+
 The only combination we actually enforce is a `static_assert` on both `impl::ProxyField` and `impl::SkeletonField`: a
 field must have at least one of `WithGetter` or `WithNotifier`. Without one of them the consumer has no way to observe
 the value, which makes the field useless. We deliberately do not require a setter, since a read-only field is perfectly normal and the provider always sets the

score/mw/com/impl/bindings/lola/skeleton_event_properties.h

@@ -14,10 +14,15 @@
 #define SCORE_MW_COM_IMPL_BINDINGS_LOLA_SKELETON_EVENT_PROPERTIES_H
 
 #include <cstddef>
+#include <cstdint>
 
 namespace score::mw::com::impl::lola
 {
 
+/// \brief Slot count a field without a notifier uses for its backing event: one slot for the current value, one so
+/// Update() can write concurrently.
+constexpr std::uint16_t kSlotCountForFieldWithoutNotifier{2U};
+
 struct SkeletonEventProperties
 {
     std::size_t number_of_slots;

score/mw/com/impl/configuration/README.md

@@ -387,6 +387,10 @@ The properties of a field or an event object on the instance level are:
   `numberOfSampleSlots`. I.e. The sum of all `maxSamples` values of all subscribing consumers must not exceed
   `numberOfSampleSlots`. Otherwise, the subscribe call will be rejected. However, this check is not ASIL level
   overarching. See explanation in the `maxSubscribers` section below.
+  **Note**: For a field without `WithNotifier` this property is ignored, since no consumer can subscribe to it.
+  The provider always uses 2 slots there: one for the current value and one so `Update()` can write concurrently.
+  If a value is configured anyway, a warning is logged. See the
+  [events and fields design](../../design/events_fields/README.md) for details.
 - `maxSubscribers`: (mandatory on provider side) - how many consumers are allowed to subscribe to this event or field.
   This number is the combined number of `QM` and `ASIL-B` consumers.
   **Note**: The maximum number of subscribers can't currently be supervised ASIL level **overarching**. I.e. in case of

score/mw/com/impl/field_tags.h

@@ -13,6 +13,7 @@
 #ifndef SCORE_MW_COM_IMPL_FIELD_TAGS_H
 #define SCORE_MW_COM_IMPL_FIELD_TAGS_H
 
+#include <cstdint>
 #include <type_traits>
 
 namespace score::mw::com::impl
@@ -32,6 +33,14 @@ struct WithNotifier
 {
 };
 
+/// \brief Runtime form of the WithNotifier tag, for places the tag pack cannot reach (e.g. the binding
+/// factories).
+enum class FieldNotifier : std::uint8_t
+{
+    kEnabled = 0U,
+    kDisabled
+};
+
 template <typename TargetType, typename... Tags>
 struct contains_type : std::disjunction<std::is_same<TargetType, Tags>...>
 {

score/mw/com/impl/plumbing/BUILD

@@ -255,6 +255,7 @@ cc_library(
         "//score/mw/com/impl/plumbing:__subpackages__",
     ],
     deps = [
+        "//score/mw/com/impl:field_tags",
         "//score/mw/com/impl:instance_identifier",
         "//score/mw/com/impl:skeleton_base",
         "@score_baselibs//score/language/futurecpp",
@@ -408,6 +409,7 @@ cc_library(
     deps = [
         ":i_skeleton_field_binding_factory",
         ":skeleton_service_element_binding_factory_impl",
+        "//score/mw/com/impl:field_tags",
         "@score_baselibs//score/language/futurecpp",
     ],
 )
@@ -509,6 +511,7 @@ cc_library(
     deps = [
         "skeleton_field_binding_factory_impl",
         ":i_skeleton_field_binding_factory",
+        "//score/mw/com/impl:field_tags",
         "@score_baselibs//score/language/futurecpp",
     ],
 )
@@ -614,6 +617,7 @@ cc_library(
     ],
     deps = [
         ":i_skeleton_field_binding_factory",
+        "//score/mw/com/impl:field_tags",
         "@googletest//:gtest",
     ],
 )
@@ -845,6 +849,7 @@ cc_unit_test(
         "//score/mw/com/impl/bindings/mock_binding",
         "//score/mw/com/impl/configuration/test:configuration_store",
         "//score/mw/com/impl/test:dummy_instance_identifier_builder",
+        "@score_baselibs//score/mw/log:recorder_mock",
     ],
 )
 

score/mw/com/impl/plumbing/i_skeleton_field_binding_factory.h

@@ -13,6 +13,7 @@
 #ifndef SCORE_MW_COM_IMPL_PLUMBING_I_SKELETON_FIELD_BINDING_FACTORY_H
 #define SCORE_MW_COM_IMPL_PLUMBING_I_SKELETON_FIELD_BINDING_FACTORY_H
 
+#include "score/mw/com/impl/field_tags.h"
 #include "score/mw/com/impl/handle_type.h"
 #include "score/mw/com/impl/instance_identifier.h"
 #include "score/mw/com/impl/skeleton_base.h"
@@ -44,10 +45,12 @@ class ISkeletonFieldBindingFactory
     /// \param identifier The instance identifier containing the binding information.
     /// \param parent A reference to the Skeleton which owns this event.
     /// \param field_name The binding unspecific name of the field inside the skeleton denoted by instance identifier.
+    /// \param field_notifier An enum indicating whether the field was declared with WithNotifier or not.
     /// \return An instance of SkeletonEventBinding or nullptr in case of an error.
     virtual auto CreateEventBinding(const InstanceIdentifier& identifier,
                                     SkeletonBinding& parent_binding,
-                                    const std::string_view field_name) noexcept
+                                    const std::string_view field_name,
+                                    const FieldNotifier field_notifier) noexcept
         -> std::unique_ptr<SkeletonEventBinding<SampleType>> = 0;
 };
 

score/mw/com/impl/plumbing/skeleton_event_binding_factory_impl.h

@@ -54,9 +54,8 @@ auto SkeletonEventBindingFactoryImpl<SampleType>::Create(const InstanceIdentifie
                                                          const std::string_view event_name) noexcept
     -> std::unique_ptr<SkeletonEventBinding<SampleType>>
 {
-    return CreateSkeletonEventOrField<SkeletonEventBinding<SampleType>,
-                                      lola::SkeletonEvent<SampleType>,
-                                      ServiceElementType::EVENT>(identifier, parent_binding, event_name);
+    return CreateSkeletonEvent<SkeletonEventBinding<SampleType>, lola::SkeletonEvent<SampleType>>(
+        identifier, parent_binding, event_name);
 }
 
 }  // namespace score::mw::com::impl

score/mw/com/impl/plumbing/skeleton_field_binding_factory.h

@@ -16,6 +16,7 @@
 #include "score/mw/com/impl/bindings/lola/element_fq_id.h"
 #include "score/mw/com/impl/bindings/lola/skeleton_event.h"
 #include "score/mw/com/impl/configuration/service_type_deployment.h"
+#include "score/mw/com/impl/field_tags.h"
 #include "score/mw/com/impl/instance_identifier.h"
 #include "score/mw/com/impl/plumbing/i_skeleton_field_binding_factory.h"
 #include "score/mw/com/impl/plumbing/skeleton_field_binding_factory_impl.h"
@@ -39,9 +40,10 @@ class SkeletonFieldBindingFactory final
     /// \brief See documentation in ISkeletonFieldBindingFactory.
     static std::unique_ptr<SkeletonEventBinding<SampleType>> CreateEventBinding(const InstanceIdentifier& identifier,
                                                                                 SkeletonBinding& parent_binding,
-                                                                                const std::string_view field_name)
+                                                                                const std::string_view field_name,
+                                                                                const FieldNotifier field_notifier)
     {
-        return instance().CreateEventBinding(identifier, parent_binding, field_name);
+        return instance().CreateEventBinding(identifier, parent_binding, field_name, field_notifier);
     }
 
     /// \brief Inject a mock ISkeletonFieldBindingFactory. If a mock is injected, then all calls on

score/mw/com/impl/plumbing/skeleton_field_binding_factory_impl.h

@@ -15,13 +15,17 @@
 
 #include "score/mw/com/impl/bindings/lola/element_fq_id.h"
 #include "score/mw/com/impl/bindings/lola/skeleton_event.h"
+#include "score/mw/com/impl/bindings/lola/skeleton_event_properties.h"
+#include "score/mw/com/impl/field_tags.h"
 #include "score/mw/com/impl/instance_identifier.h"
 #include "score/mw/com/impl/plumbing/i_skeleton_field_binding_factory.h"
 #include "score/mw/com/impl/plumbing/skeleton_service_element_binding_factory_impl.h"
 #include "score/mw/com/impl/skeleton_base.h"
 #include "score/mw/com/impl/skeleton_event_binding.h"
 
+#include <cstdint>
 #include <memory>
+#include <optional>
 #include <string_view>
 
 namespace score::mw::com::impl
@@ -36,7 +40,8 @@ class SkeletonFieldBindingFactoryImpl : public ISkeletonFieldBindingFactory<Samp
     std::unique_ptr<SkeletonEventBinding<SampleType>> CreateEventBinding(
         const InstanceIdentifier& identifier,
         SkeletonBinding& parent_binding,
-        const std::string_view field_name) noexcept override;
+        const std::string_view field_name,
+        const FieldNotifier field_notifier) noexcept override;
 };
 
 template <typename SampleType>
@@ -50,12 +55,16 @@ template <typename SampleType>
 // coverity[autosar_cpp14_a15_5_3_violation : FALSE]
 auto SkeletonFieldBindingFactoryImpl<SampleType>::CreateEventBinding(const InstanceIdentifier& identifier,
                                                                      SkeletonBinding& parent_binding,
-                                                                     const std::string_view field_name) noexcept
+                                                                     const std::string_view field_name,
+                                                                     const FieldNotifier field_notifier) noexcept
     -> std::unique_ptr<SkeletonEventBinding<SampleType>>
 {
-    return CreateSkeletonEventOrField<SkeletonEventBinding<SampleType>,
-                                      lola::SkeletonEvent<SampleType>,
-                                      ServiceElementType::FIELD>(identifier, parent_binding, field_name);
+    const std::optional<LolaEventInstanceDeployment::SampleSlotCountType> slot_count_override =
+        field_notifier == FieldNotifier::kDisabled
+            ? std::optional<LolaEventInstanceDeployment::SampleSlotCountType>{lola::kSlotCountForFieldWithoutNotifier}
+            : std::nullopt;
+    return CreateSkeletonField<SkeletonEventBinding<SampleType>, lola::SkeletonEvent<SampleType>>(
+        identifier, parent_binding, field_name, slot_count_override);
 }
 
 }  // namespace score::mw::com::impl

score/mw/com/impl/plumbing/skeleton_field_binding_factory_mock.h

@@ -13,6 +13,7 @@
 #ifndef SCORE_MW_COM_IMPL_PLUMBING_SKELETON_FIELD_BINDING_FACTORY_MOCK_H
 #define SCORE_MW_COM_IMPL_PLUMBING_SKELETON_FIELD_BINDING_FACTORY_MOCK_H
 
+#include "score/mw/com/impl/field_tags.h"
 #include "score/mw/com/impl/plumbing/i_skeleton_field_binding_factory.h"
 
 #include <gmock/gmock.h>
@@ -26,7 +27,7 @@ class SkeletonFieldBindingFactoryMock : public ISkeletonFieldBindingFactory<Samp
   public:
     MOCK_METHOD(std::unique_ptr<SkeletonEventBinding<SampleType>>,
                 CreateEventBinding,
-                (const InstanceIdentifier&, SkeletonBinding&, const std::string_view),
+                (const InstanceIdentifier&, SkeletonBinding&, const std::string_view, const FieldNotifier),
                 (noexcept, override));
 };