Back out "[folly] Avoid executor re-queue in collect[All]SemiFuture"

Summary: Original commit changeset: e533bfa6b9d2

Reviewed By: heslami

Differential Revision: D14818275

fbshipit-source-id: 06ecb8058538ca150b941df56a050cf572f7eeea

folly/futures/Future-inl.h

@@ -1548,8 +1548,7 @@ collectAllSemiFuture(Fs&&... fs) {
   auto ctx = std::make_shared<Context>();
   futures::detail::foreach(
       [&](auto i, auto&& f) {
-        auto g = std::move(f).via(&InlineExecutor::instance());
-        g.setCallback_([i, ctx](auto&& t) {
+        f.setCallback_([i, ctx](auto&& t) {
           std::get<i.value>(ctx->results) = std::move(t);
         });
       },
@@ -1598,8 +1597,8 @@ collectAllSemiFuture(InputIterator first, InputIterator last) {
   auto ctx = std::make_shared<Context>(size_t(std::distance(first, last)));
 
   for (size_t i = 0; first != last; ++first, ++i) {
-    auto f = std::move(*first).via(&InlineExecutor::instance());
-    f.setCallback_([i, ctx](Try<T>&& t) { ctx->results[i] = std::move(t); });
+    first->setCallback_(
+        [i, ctx](Try<T>&& t) { ctx->results[i] = std::move(t); });
   }
 
   auto future = ctx->p.getSemiFuture();
@@ -1658,8 +1657,7 @@ collectSemiFuture(InputIterator first, InputIterator last) {
 
   auto ctx = std::make_shared<Context>(std::distance(first, last));
   for (size_t i = 0; first != last; ++first, ++i) {
-    auto f = std::move(*first).via(&InlineExecutor::instance());
-    f.setCallback_([i, ctx](Try<T>&& t) {
+    first->setCallback_([i, ctx](Try<T>&& t) {
       if (t.hasException()) {
         if (!ctx->threw.exchange(true, std::memory_order_relaxed)) {
           ctx->p.setException(std::move(t.exception()));
@@ -1714,8 +1712,7 @@ collectSemiFuture(Fs&&... fs) {
   auto ctx = std::make_shared<Context>();
   futures::detail::foreach(
       [&](auto i, auto&& f) {
-        auto g = std::move(f).via(&InlineExecutor::instance());
-        g.setCallback_([i, ctx](auto&& t) {
+        f.setCallback_([i, ctx](auto&& t) {
           if (t.hasException()) {
             if (!ctx->threw.exchange(true, std::memory_order_relaxed)) {
               ctx->p.setException(std::move(t.exception()));

folly/futures/test/CollectTest.cpp

@@ -30,13 +30,6 @@ static eggs_t eggs("eggs");
 
 auto rng = std::mt19937(folly::randomNumberSeed());
 
-class NoAddExecutor : public folly::Executor {
- public:
-  void add(Func) override {
-    throw eggs;
-  }
-};
-
 TEST(Collect, collectAll) {
   // returns a vector variant
   {
@@ -786,43 +779,6 @@ TEST(Collect, collectAllNone) {
   EXPECT_TRUE(f.isReady());
 }
 
-TEST(Collect, collectNoRequeue) {
-  NoAddExecutor executor;
-  std::vector<Future<int>> futures;
-  for (int i = 0; i < 10; ++i) {
-    futures.emplace_back(makeFuture(i).via(&executor));
-  }
-  EXPECT_NO_THROW(collect(futures).get());
-}
-
-TEST(Collect, collectVariadicNoRequeue) {
-  NoAddExecutor executor;
-  auto f1 = makeFuture(0).via(&executor);
-  auto f2 = makeFuture(1).via(&executor);
-  EXPECT_NO_THROW(collect(f1, f2).get());
-}
-
-TEST(Collect, collectAllNoRequeue) {
-  NoAddExecutor executor;
-  std::vector<Future<int>> futures;
-  for (int i = 0; i < 10; ++i) {
-    futures.emplace_back(makeFuture(i).via(&executor));
-  }
-  auto results = collectAll(futures).get();
-  for (auto& t : results) {
-    EXPECT_FALSE(t.hasException());
-  }
-}
-
-TEST(Collect, collectAllVariadicNoRequeue) {
-  NoAddExecutor executor;
-  auto f1 = makeFuture(0).via(&executor);
-  auto f2 = makeFuture(1).via(&executor);
-  auto results = collectAll(f1, f2).get();
-  EXPECT_FALSE(std::get<0>(results).hasException());
-  EXPECT_FALSE(std::get<1>(results).hasException());
-}
-
 TEST(Collect, noDefaultConstructor) {
   struct A {
     explicit A(size_t /* x */) {}