1 files changed, 80 insertions, 0 deletions
diff --git a/widget/windows/filedialog/WinFileDialogParent.cpp b/widget/windows/filedialog/WinFileDialogParent.cpp
index 2c256a1506..329c72cc94 100644
--- a/widget/windows/filedialog/WinFileDialogParent.cpp
+++ b/widget/windows/filedialog/WinFileDialogParent.cpp
@@ -54,6 +54,86 @@ PWinFileDialogParent::nsresult WinFileDialogParent::BindToUtilityProcess(
   return NS_OK;
 }
 
+// Convert the raw IPC promise-type to a filedialog::Promise.
+template <typename T, typename Ex, size_t N>
+static auto ConvertToFDPromise(
+    const char (&aMethod)[N],  // __func__
+    Ex&& extractor,
+    RefPtr<MozPromise<T, mozilla::ipc::ResponseRejectReason, true>>
+        aSrcPromise) {
+  // The extractor must produce a `mozilla::Result<..., Error>` from `T`.
+  using SrcResultInfo = detail::DestructureResult<std::invoke_result_t<Ex, T>>;
+  using ResolveT = typename SrcResultInfo::OkT;
+  static_assert(std::is_same_v<typename SrcResultInfo::ErrorT, Error>,
+                "expected T to be a Result<..., Error>");
+
+  using SrcPromiseT = MozPromise<T, mozilla::ipc::ResponseRejectReason, true>;
+  using DstPromiseT = MozPromise<ResolveT, Error, true>;
+
+  RefPtr<DstPromiseT> ret = aSrcPromise->Then(
+      mozilla::GetCurrentSerialEventTarget(), aMethod,
+
+      [extractor, aMethod](T&& val) {
+        mozilla::Result<ResolveT, Error> result = extractor(std::move(val));
+        if (result.isOk()) {
+          return DstPromiseT::CreateAndResolve(result.unwrap(), aMethod);
+        }
+        return DstPromiseT::CreateAndReject(result.unwrapErr(), aMethod);
+      },
+      [aMethod](typename mozilla::ipc::ResponseRejectReason&& val) {
+        return DstPromiseT::CreateAndReject(
+            MOZ_FD_ERROR(IPCError, "IPC", (uint32_t)val), aMethod);
+      });
+
+  return ret;
+}
+
+template <typename Input, typename Output>
+struct Extractor {
+  template <typename Input::Type tag_, Output const& (Input::*getter_)() const>
+  static auto get() {
+    return [](Input&& res) -> Result<Output, Error> {
+      if (res.type() == tag_) {
+        return (res.*getter_)();
+      }
+      if (res.type() == Input::TRemoteError) {
+        RemoteError err = res.get_RemoteError();
+        return Err(Error{.kind = Error::RemoteError,
+                         .where = Error::Location::Deserialize(err.where()),
+                         .why = err.why()});
+      }
+      MOZ_ASSERT_UNREACHABLE("internal IPC failure?");
+      return Err(MOZ_FD_ERROR(IPCError, "internal IPC failure?", E_FAIL));
+    };
+  }
+};
+
+[[nodiscard]] RefPtr<WinFileDialogParent::ShowFileDialogPromise>
+WinFileDialogParent::ShowFileDialogImpl(HWND parent, const FileDialogType& type,
+                                        mozilla::Span<Command const> commands) {
+  auto inner_promise = PWinFileDialogParent::SendShowFileDialog(
+      reinterpret_cast<WindowsHandle>(parent), type, std::move(commands));
+
+  return ConvertToFDPromise(
+      __func__,
+      Extractor<FileResult, Maybe<Results>>::get<
+          FileResult::TMaybeResults, &FileResult::get_MaybeResults>(),
+      std::move(inner_promise));
+}
+
+[[nodiscard]] RefPtr<WinFileDialogParent::ShowFolderDialogPromise>
+WinFileDialogParent::ShowFolderDialogImpl(
+    HWND parent, mozilla::Span<Command const> commands) {
+  auto inner_promise = PWinFileDialogParent::SendShowFolderDialog(
+      reinterpret_cast<WindowsHandle>(parent), std::move(commands));
+
+  return ConvertToFDPromise(
+      __func__,
+      Extractor<FolderResult, Maybe<nsString>>::get<
+          FolderResult::TMaybensString, &FolderResult::get_MaybensString>(),
+      std::move(inner_promise));
+}
+
 void WinFileDialogParent::ProcessingError(Result aCode, const char* aReason) {
   detail::LogProcessingError(sLogFileDialog, this, aCode, aReason);
 }