Move FunctionView to library/cpp/yt/memory and add unit tests

0f22987a2824410add2233f4434e26c9e1903da1

4 files changed, 195 insertions, 0 deletions

diff --git a/library/cpp/yt/misc/function_view-inl.h b/library/cpp/yt/memory/function_view-inl.h
index ececfdf335..ececfdf335 100644
--- a/library/cpp/yt/misc/function_view-inl.h
+++ b/library/cpp/yt/memory/function_view-inl.h
diff --git a/library/cpp/yt/misc/function_view.h b/library/cpp/yt/memory/function_view.h
index 259238521f..259238521f 100644
--- a/library/cpp/yt/misc/function_view.h
+++ b/library/cpp/yt/memory/function_view.h
diff --git a/library/cpp/yt/memory/unittests/function_view_ut.cpp b/library/cpp/yt/memory/unittests/function_view_ut.cpp
new file mode 100644
index 0000000000..99af41793c
--- /dev/null
+++ b/library/cpp/yt/memory/unittests/function_view_ut.cpp
@@ -0,0 +1,194 @@
+#include <library/cpp/testing/gtest/gtest.h>
+
+#include <library/cpp/yt/memory/function_view.h>
+
+#include <util/generic/string.h>
+#include <util/string/cast.h>
+
+namespace NYT {
+namespace {
+
+////////////////////////////////////////////////////////////////////////////////
+
+struct TNoCopy
+{
+    int Value = 42;
+
+    TNoCopy() = default;
+
+    TNoCopy(const TNoCopy&) = delete;
+
+    TNoCopy(TNoCopy&&)
+    { }
+};
+
+int Foo()
+{
+    return 42;
+}
+
+int& Bar()
+{
+    static int bar = 0;
+    return bar;
+}
+
+const TNoCopy& ImmutBar()
+{
+    static TNoCopy bar = {};
+    return bar;
+}
+
+TString Baz(const int& x)
+{
+    return ToString(x);
+}
+
+void NoExFoo() noexcept
+{ }
+
+struct TCallable
+{
+    int InvocationCount = 0;
+    mutable int ConstInvocationCount = 0;
+
+    void operator()() &
+    {
+        ++InvocationCount;
+    }
+
+    void operator()() const &
+    {
+        ++ConstInvocationCount;
+    }
+};
+
+////////////////////////////////////////////////////////////////////////////////
+
+TEST(TFunctionViewTest, JustWorks)
+{
+    auto stackLambda = [] (int val) {
+        return val + 1;
+    };
+
+    {
+        TFunctionView<int(int)> view(stackLambda);
+
+        EXPECT_EQ(view(42), 43);
+    }
+}
+
+TEST(TFunctionViewTest, FreeFunction)
+{
+    TFunctionView<int()> view(Foo);
+    EXPECT_EQ(view(), 42);
+}
+
+TEST(TFunctionViewTest, RefReturn)
+{
+    TFunctionView<int&()> view(Bar);
+    ++view();
+    EXPECT_EQ(view(), 1);
+
+    TFunctionView<const TNoCopy&()> immut_view(ImmutBar);
+    EXPECT_EQ(immut_view().Value, 42);
+}
+
+TEST(TFunctionViewTest, RefArgument)
+{
+    TFunctionView<TString(const int&)> view(Baz);
+    EXPECT_EQ(view(77), TString("77"));
+}
+
+TEST(TFunctionViewTest, NoExcept)
+{
+    TFunctionView<void() noexcept> view(NoExFoo);
+    static_assert(std::is_nothrow_invocable_r_v<void, decltype(view)>);
+
+    view();
+}
+
+TEST(TFunctionViewTest, CVOverloads)
+{
+    TCallable callable;
+
+    TFunctionView<void()> view(callable);
+    // NB: & overload overshadows every other overload.
+    // const auto& viewRef = view;
+    // viewRef();
+
+    view();
+    EXPECT_EQ(callable.InvocationCount, 1);
+    EXPECT_EQ(callable.ConstInvocationCount, 0);
+}
+
+TEST(TFunctionViewTest, CopyView)
+{
+    int counter = 0;
+    auto lambda = [&counter] {
+        ++counter;
+    };
+
+    TFunctionView<void()> view1(lambda);
+    TFunctionView<void()> view2 = view1;
+
+    view1();
+    EXPECT_EQ(counter, 1);
+    view2();
+    EXPECT_EQ(counter, 2);
+    view1();
+    EXPECT_EQ(counter, 3);
+}
+
+TEST(TFunctionViewTest, AssignView)
+{
+    int counter = 0;
+    auto lambda = [&counter] {
+        ++counter;
+    };
+
+    TFunctionView<void()> view(lambda);
+    view();
+    EXPECT_EQ(counter, 1);
+
+    {
+        auto innerCounter = 0;
+        auto lambda = [&innerCounter] {
+            ++innerCounter;
+        };
+
+        view = lambda;
+        view();
+        EXPECT_EQ(counter, 1);
+        EXPECT_EQ(innerCounter, 1);
+    }
+
+    // NB: Even though object is dead view will remain "valid".
+    // Be careful with lifetimes!
+    EXPECT_TRUE(view.IsValid());
+}
+
+TEST(TFunctionViewTest, ReleaseSemantics)
+{
+    int counter = 0;
+    auto lambda = [&counter] {
+        ++counter;
+    };
+
+    TFunctionView<void()> view1(lambda);
+    view1();
+    EXPECT_EQ(counter, 1);
+
+    TFunctionView view2 = view1.Release();
+    EXPECT_FALSE(view1.IsValid());
+
+    EXPECT_TRUE(view2.IsValid());
+
+    view2();
+    EXPECT_EQ(counter, 2);
+}
+
+////////////////////////////////////////////////////////////////////////////////
+
+} // namespace
+} // namespace NYT
diff --git a/library/cpp/yt/memory/unittests/ya.make b/library/cpp/yt/memory/unittests/ya.make
index 3658eefce1..4c3e4d5303 100644
--- a/library/cpp/yt/memory/unittests/ya.make
+++ b/library/cpp/yt/memory/unittests/ya.make
@@ -12,6 +12,7 @@ SRCS(
     chunked_memory_pool_allocator_ut.cpp
     chunked_memory_pool_output_ut.cpp
     free_list_ut.cpp
+    function_view_ut.cpp
     intrusive_ptr_ut.cpp
     shared_range_ut.cpp
     weak_ptr_ut.cpp