callback_promise_adapter.h | Explore in Territory

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#ifndef THIRD_PARTY_BLINK_RENDERER_BINDINGS_CORE_V8_CALLBACK_PROMISE_ADAPTER_H_
#define THIRD_PARTY_BLINK_RENDERER_BINDINGS_CORE_V8_CALLBACK_PROMISE_ADAPTER_H_

#include <memory>
#include <utility>

#include "third_party/blink/public/platform/web_callbacks.h"
#include "third_party/blink/renderer/bindings/core/v8/idl_types.h"
#include "third_party/blink/renderer/bindings/core/v8/script_promise_resolver.h"
#include "third_party/blink/renderer/platform/wtf/type_traits.h"

namespace blink {

// CallbackPromiseAdapter is a WebCallbacks subclass and resolves / rejects the
// stored resolver when onSuccess / onError is called, respectively.
//
// Basically CallbackPromiseAdapter<S, T> is a subclass of
// WebCallbacks<S::WebType, T::WebType>. There are some exceptions:
//  - If S or T don't have WebType (e.g. S = bool), a default WebType holder
//    called trivial WebType holder is used. For example,
//    CallbackPromiseAdapter<bool, void> is a subclass of
//    WebCallbacks<bool, void>.
//  - If a WebType is std::unique_ptr<T>, its corresponding type parameter on
//    WebCallbacks is std::unique_ptr<T>, because WebCallbacks must be exposed
//    to Chromium.
//
// When onSuccess is called with a S::WebType value, the value is passed to
// S::take and the resolver is resolved with its return value. Ditto for
// onError.
//
// Example:
// class MyClass {
// public:
//     using WebType = std::unique_ptr<WebMyClass>;
//     static scoped_refptr<MyClass> take(ScriptPromiseResolverBase* resolver,
//         std::unique_ptr<WebMyClass> webInstance)
//     {
//         return MyClass::create(webInstance);
//     }
//     ...
// };
// class MyErrorClass {
// public:
//     using WebType = const WebMyErrorClass&;
//     static MyErrorClass take(ScriptPromiseResolverBase* resolver,
//         const WebErrorClass& webError)
//     {
//         return MyErrorClass(webError);
//     }
//     ...
// };
// std::unique_ptr<WebCallbacks<std::unique_ptr<WebMyClass>,
//                 const WebMyErrorClass&>>
//     callbacks =
//         std::make_unique<CallbackPromiseAdapter<MyClass, MyErrorClass>>(
//             resolver);
// ...
//
// std::unique_ptr<WebCallbacks<bool, const WebMyErrorClass&>> callbacks2 =
//     std::make_unique<CallbackPromiseAdapter<bool, MyErrorClass>>(resolver);
// ...
//
//
// In order to implement the above exceptions, we have template classes below.
// Base and OnErrorAdapter provide onSuccess and onError
// implementation, and there are utility templates that provide the trivial
// WebType holder.

namespace internal {

// This template is placed outside of CallbackPromiseAdapterInternal because
// explicit specialization is forbidden in a class scope.
template <typename T>
struct CallbackPromiseAdapterTrivialWebTypeHolder { … };
template <>
struct CallbackPromiseAdapterTrivialWebTypeHolder<void> { … };

class CallbackPromiseAdapterInternal { … };

}  // namespace internal

CallbackPromiseAdapter;

}  // namespace blink

#endif  // THIRD_PARTY_BLINK_RENDERER_BINDINGS_CORE_V8_CALLBACK_PROMISE_ADAPTER_H_
chromium/third_party/blink/renderer/bindings/core/v8/callback_promise_adapter.h
