feat userver: implement data_provider

commit_hash:41d39f49c4499c0d36016cb51adf560a7505b7ff

Author: svetoch

.mapping.json

@@ -801,6 +801,7 @@
   "core/include/userver/cache/cache_statistics.hpp":"taxi/uservices/userver/core/include/userver/cache/cache_statistics.hpp",
   "core/include/userver/cache/cache_update_trait.hpp":"taxi/uservices/userver/core/include/userver/cache/cache_update_trait.hpp",
   "core/include/userver/cache/caching_component_base.hpp":"taxi/uservices/userver/core/include/userver/cache/caching_component_base.hpp",
+  "core/include/userver/cache/data_provider.hpp":"taxi/uservices/userver/core/include/userver/cache/data_provider.hpp",
   "core/include/userver/cache/exceptions.hpp":"taxi/uservices/userver/core/include/userver/cache/exceptions.hpp",
   "core/include/userver/cache/expirable_lru_cache.hpp":"taxi/uservices/userver/core/include/userver/cache/expirable_lru_cache.hpp",
   "core/include/userver/cache/lru_cache_component_base.hpp":"taxi/uservices/userver/core/include/userver/cache/lru_cache_component_base.hpp",
@@ -2055,6 +2056,7 @@
   "core/sys_coro/include/coroutines/coroutine.hpp":"taxi/uservices/userver/core/sys_coro/include/coroutines/coroutine.hpp",
   "core/uboost_coro/include/coroutines/coroutine.hpp":"taxi/uservices/userver/core/uboost_coro/include/coroutines/coroutine.hpp",
   "core/utest/CMakeLists.txt":"taxi/uservices/userver/core/utest/CMakeLists.txt",
+  "core/utest/include/userver/cache/data_provider_mock.hpp":"taxi/uservices/userver/core/utest/include/userver/cache/data_provider_mock.hpp",
   "core/utest/include/userver/cache/statistics_mock.hpp":"taxi/uservices/userver/core/utest/include/userver/cache/statistics_mock.hpp",
   "core/utest/include/userver/dump/operations_mock.hpp":"taxi/uservices/userver/core/utest/include/userver/dump/operations_mock.hpp",
   "core/utest/include/userver/dump/test_helpers.hpp":"taxi/uservices/userver/core/utest/include/userver/dump/test_helpers.hpp",

core/include/userver/cache/caching_component_base.hpp

@@ -10,6 +10,7 @@
 #include <fmt/format.h>
 
 #include <userver/cache/cache_update_trait.hpp>
+#include <userver/cache/data_provider.hpp>
 #include <userver/cache/exceptions.hpp>
 #include <userver/compiler/demangle.hpp>
 #include <userver/components/component_base.hpp>
@@ -150,7 +151,7 @@ namespace components {
 
 template <typename T>
 // NOLINTNEXTLINE(fuchsia-multiple-inheritance)
-class CachingComponentBase : public ComponentBase, protected cache::CacheUpdateTrait {
+class CachingComponentBase : public ComponentBase, public cache::DataProvider<T>, protected cache::CacheUpdateTrait {
 public:
     CachingComponentBase(const ComponentConfig& config, const ComponentContext&);
     ~CachingComponentBase() override;
@@ -165,7 +166,7 @@ class CachingComponentBase : public ComponentBase, protected cache::CacheUpdateT
     /// returns `true`.
     /// @throws cache::EmptyCacheError if the contents are `nullptr`, and
     /// `MayReturnNull` returns `false` (which is the default behavior).
-    utils::SharedReadablePtr<T> Get() const;
+    utils::SharedReadablePtr<T> Get() const final;
 
     /// @return cache contents. May be nullptr regardless of `MayReturnNull`.
     utils::SharedReadablePtr<T> GetUnsafe() const;
@@ -181,16 +182,24 @@ class CachingComponentBase : public ComponentBase, protected cache::CacheUpdateT
     static yaml_config::Schema GetStaticConfigSchema();
 
 protected:
-    /// Sets the new value of cache. As a result the Get() member function starts
-    /// returning the value passed into this function after the Update() finishes.
+    /// Sets the new value of cache. As a result the `Get()` member function starts
+    /// returning the value passed into this function after the `Update()` finishes.
     ///
-    /// @warning Do not forget to update cache::UpdateStatisticsScope, otherwise
+    /// @warning Do not forget to update @ref cache::UpdateStatisticsScope, otherwise
     /// the behavior is undefined.
     void Set(std::unique_ptr<const T> value_ptr);
 
     /// @overload
     void Set(T&& value);
 
+    /// Attach the value of cache. As a result the `Get()` member function starts returning the value passed into
+    /// this function after the `Update()` finishes. Does not take over into sole ownership. Do not use unless
+    /// absolutely necessary. The object must be strictly thread-safe.
+    ///
+    /// @warning Do not forget to update @ref cache::UpdateStatisticsScope, otherwise
+    /// the behavior is undefined.
+    void Attach(const std::shared_ptr<const T>& value_ptr);
+
     /// @overload Set()
     template <typename... Args>
     void Emplace(Args&&... args);
@@ -284,8 +293,16 @@ utils::SharedReadablePtr<T> CachingComponentBase<T>::GetUnsafe() const {
 
 template <typename T>
 void CachingComponentBase<T>::Set(std::unique_ptr<const T> value_ptr) {
-    const std::shared_ptr<const T> new_value = TransformNewValue(std::move(value_ptr));
+    Attach(TransformNewValue(std::move(value_ptr)));
+}
 
+template <typename T>
+void CachingComponentBase<T>::Set(T&& value) {
+    Emplace(std::move(value));
+}
+
+template <typename T>
+void CachingComponentBase<T>::Attach(const std::shared_ptr<const T>& new_value) {
     if (HasPreAssignCheck()) {
         auto old_value = cache_.Read();
         PreAssignCheck(old_value->get(), new_value.get());
@@ -296,11 +313,6 @@ void CachingComponentBase<T>::Set(std::unique_ptr<const T> value_ptr) {
     OnCacheModified();
 }
 
-template <typename T>
-void CachingComponentBase<T>::Set(T&& value) {
-    Emplace(std::move(value));
-}
-
 template <typename T>
 template <typename... Args>
 void CachingComponentBase<T>::Emplace(Args&&... args) {

core/include/userver/cache/data_provider.hpp

@@ -0,0 +1,31 @@
+#pragma once
+
+/// @file userver/cache/data_provider.hpp
+/// @brief A simple interface for hiding implementation and making mocks easy to implement
+
+#include <userver/utils/shared_readable_ptr.hpp>
+
+USERVER_NAMESPACE_BEGIN
+
+namespace cache {
+
+/// @brief Interface for providing cached data of type T
+/// @tparam T The type of data being provided
+///
+/// DataProvider is a simple interface that allows hiding implementation
+/// details and making mocks easy to implement. It provides a way to
+/// retrieve shared readable pointers to cached data.
+
+template <typename T>
+class DataProvider {
+public:
+    using DataType = T;
+
+    virtual ~DataProvider() = default;
+
+    virtual utils::SharedReadablePtr<DataType> Get() const = 0;
+};
+
+}  // namespace cache
+
+USERVER_NAMESPACE_END

core/utest/include/userver/cache/data_provider_mock.hpp

@@ -0,0 +1,37 @@
+#pragma once
+
+/// @file userver/cache/data_provider_mock.hpp
+/// @brief Mock implementation of DataProvider
+
+#include <userver/cache/data_provider.hpp>
+
+USERVER_NAMESPACE_BEGIN
+
+namespace cache {
+
+/// @brief Mock implementation of DataProvider for testing purposes
+/// @tparam T The type of data being provided
+///
+/// DataProviderMock is a mock implementation of the DataProvider interface
+/// that stores static data and returns shared readable pointers to it.
+/// It's designed for use in unit tests where you want to provide
+/// controlled data to components that depend on DataProvider.
+template <typename T>
+class DataProviderMock : public DataProvider<T> {
+public:
+    using DataProvider<T>::DataType;
+
+    explicit DataProviderMock(DataType data) : data_{std::make_shared<DataType>(std::move(data))} {}
+    explicit DataProviderMock(std::shared_ptr<DataType> data) : data_{std::move(data)} {}
+
+    utils::SharedReadablePtr<DataType> Get() const final {
+        return utils::SharedReadablePtr<DataType>(data_.ReadCopy());
+    };
+
+private:
+    rcu::Variable<std::shared_ptr<const DataType>> data_;
+};
+
+}  // namespace cache
+
+USERVER_NAMESPACE_END