Use (un)expected for network fetch

3 files changed, 11 insertions, 13 deletions

diff --git a/src/other_tools/ops_maps/content_cas_map.cpp b/src/other_tools/ops_maps/content_cas_map.cpp
index 651e83fb..013f49c6 100644
--- a/src/other_tools/ops_maps/content_cas_map.cpp
+++ b/src/other_tools/ops_maps/content_cas_map.cpp
@@ -41,15 +41,13 @@ void FetchFromNetwork(ArchiveContent const& key,
         return;
     }
     // now do the actual fetch
-    auto res = NetworkFetchWithMirrors(
+    auto data = NetworkFetchWithMirrors(
         key.fetch_url, key.mirrors, ca_info, additional_mirrors);
-    auto* data =
-        std::get_if<1>(&res);  // get pointer to fetched data, or nullptr
-    if (data == nullptr) {
+    if (not data) {
         (*logger)(fmt::format("Failed to fetch a file with id {} from provided "
                               "remotes:{}",
                               key.content,
-                              std::get<0>(res)),
+                              data.error()),
                   /*fatal=*/true);
         return;
     }
diff --git a/src/other_tools/utils/TARGETS b/src/other_tools/utils/TARGETS
index e210f901..27cbb93d 100644
--- a/src/other_tools/utils/TARGETS
+++ b/src/other_tools/utils/TARGETS
@@ -48,6 +48,7 @@
     , ["src/buildtool/crypto", "hasher"]
     , ["src/buildtool/logging", "log_level"]
     , ["src/other_tools/just_mr", "mirrors"]
+    , ["src/utils/cpp", "expected"]
     ]
   , "stage": ["src", "other_tools", "utils"]
   }
diff --git a/src/other_tools/utils/content.hpp b/src/other_tools/utils/content.hpp
index 15c582c4..31dd7fc1 100644
--- a/src/other_tools/utils/content.hpp
+++ b/src/other_tools/utils/content.hpp
@@ -18,7 +18,6 @@
 #include <optional>
 #include <string>
 #include <utility>  // std::move
-#include <variant>
 
 #include "src/buildtool/common/user_structs.hpp"
 #include "src/buildtool/crypto/hasher.hpp"
@@ -26,6 +25,7 @@
 #include "src/other_tools/just_mr/mirrors.hpp"
 #include "src/other_tools/utils/curl_easy_handle.hpp"
 #include "src/other_tools/utils/curl_url_handle.hpp"
+#include "src/utils/cpp/expected.hpp"
 
 // Utilities related to the content of an archive
 
@@ -44,14 +44,13 @@
 
 /// \brief Fetches a file from the internet and stores its content in memory.
 /// Tries not only a given remote, but also all associated remote locations.
-/// \returns An error + data union, with the error message at index 0 and the
-/// fetched data at index 1.
+/// \returns The fetched data on success or an unexpected error as string.
 [[nodiscard]] static auto NetworkFetchWithMirrors(
     std::string const& fetch_url,
     std::vector<std::string> const& mirrors,
     CAInfoPtr const& ca_info,
     MirrorsPtr const& additional_mirrors) noexcept
-    -> std::variant<std::string, std::string> {
+    -> expected<std::string, std::string> {
     // keep all remotes tried, to report in case fetch fails
     std::string remotes_buffer{};
     std::optional<std::string> data{std::nullopt};
@@ -81,10 +80,10 @@
         // add local mirror to buffer
         remotes_buffer.append(fmt::format("\n> {}", mirror));
     }
-    return data ? std::variant<std::string, std::string>(std::in_place_index<1>,
-                                                         *data)
-                : std::variant<std::string, std::string>(std::in_place_index<0>,
-                                                         remotes_buffer);
+    if (not data) {
+        return unexpected{remotes_buffer};
+    }
+    return *data;
 }
 
 template <Hasher::HashType type>