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LibCore: Check if a promise is already resolved in Promise::map()

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This commit is contained in:
Karol Kosek 2023-08-29 14:32:41 +02:00 committed by Andrew Kaster
parent 50d8ef94ba
commit 51fefb57fc
Notes: sideshowbarker 2024-07-16 23:59:28 +09:00 
Author: https://github.com/krkk
Commit: https://github.com/SerenityOS/serenity/commit/51fefb57fc
Pull-request: https://github.com/SerenityOS/serenity/pull/20833
Reviewed-by: https://github.com/ADKaster ✅
2 changed files with 42 additions and 2 deletions
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34
Tests/LibCore/TestLibCorePromise.cpp
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@ -61,6 +61,40 @@ TEST_CASE(promise_chain_handlers)
EXPECT(!rejected);
}
TEST_CASE(promise_map)
{
Core::EventLoop loop;
auto promise = MUST(Core::Promise<int>::try_create());
auto mapped_promise = promise->map<int>([](int result) {
return result * 2;
});
loop.deferred_invoke([=] {
promise->resolve(21);
});
auto result = mapped_promise->await();
EXPECT(!result.is_error());
EXPECT_EQ(result.value(), 42);
}
TEST_CASE(promise_map_already_resolved)
{
Core::EventLoop loop;
auto promise = MUST(Core::Promise<int>::try_create());
promise->resolve(21);
auto mapped_promise = promise->map<int>([](int result) {
return result * 2;
});
auto result = mapped_promise->await();
EXPECT(!result.is_error());
EXPECT_EQ(result.value(), 42);
}
TEST_CASE(threaded_promise_instantly_resolved)
{
Core::EventLoop loop;

10
Userland/Libraries/LibCore/Promise.h
View file

@ -60,9 +60,15 @@ public:
// Converts a Promise<A> to a Promise<B> using a function func: A -> B
template<typename T>
RefPtr<Promise<T>> map(Function<T(Result&)> func)
NonnullRefPtr<Promise<T>> map(Function<T(Result&)> func)
{
RefPtr<Promise<T>> new_promise = Promise<T>::construct();
NonnullRefPtr<Promise<T>> new_promise = Promise<T>::construct();
if (is_resolved())
new_promise->resolve(func(m_result_or_rejection->value()));
if (is_rejected())
new_promise->reject(m_result_or_rejection->release_error());
on_resolution = [new_promise, func = move(func)](Result& result) -> ErrorOr<void> {
new_promise->resolve(func(result));
return {};