serve target: Improve logic for local build failure triggers

If the serve endpoint reports an internal error, local builds
should not continue and the error message should be provided.
Similarly, if the serve endpoint promises the target cache value to
be in remote CAS, but the client cannot find or process it as
needed, then a local build again should not continue and the reason
be provided as an error message.

1 files changed, 9 insertions, 6 deletions

diff --git a/src/buildtool/serve_api/remote/target_client.cpp b/src/buildtool/serve_api/remote/target_client.cpp
index d64f24c8..67b50a84 100644
--- a/src/buildtool/serve_api/remote/target_client.cpp
+++ b/src/buildtool/serve_api/remote/target_client.cpp
@@ -100,10 +100,6 @@ auto TargetClient::ServeTarget(const TargetCacheKey& key,
     grpc::ClientContext context;
     justbuild::just_serve::ServeTargetResponse response;
     auto const& status = stub_->ServeTarget(&context, request, &response);
-    if (!status.ok()) {
-        return serve_target_result_t{std::in_place_index<1>,
-                                     StatusString(status)};
-    }
 
     // differentiate status codes
     switch (status.error_code()) {
@@ -145,7 +141,7 @@ auto TargetClient::ServeTarget(const TargetCacheKey& key,
                 auto const& result = TargetCacheEntry::FromJson(
                     nlohmann::json::parse(*target_value_str));
                 // return the target cache value information
-                return serve_target_result_t{std::in_place_index<2>,
+                return serve_target_result_t{std::in_place_index<3>,
                                              std::make_pair(result, obj_info)};
             } catch (std::exception const& ex) {
                 return serve_target_result_t{
@@ -154,13 +150,20 @@ auto TargetClient::ServeTarget(const TargetCacheKey& key,
                                 ex.what())};
             }
         }
+        case grpc::StatusCode::INTERNAL: {
+            return serve_target_result_t{
+                std::in_place_index<1>,
+                fmt::format(
+                    "Serve endpoint reported the fatal internal error:\n{}",
+                    status.error_message())};
+        }
         case grpc::StatusCode::NOT_FOUND: {
             return std::nullopt;  // this might allow a local build to continue
         }
         default:;  // fallthrough
     }
     return serve_target_result_t{
-        std::in_place_index<1>,
+        std::in_place_index<2>,
         fmt::format("Serve endpoint failed with:\n{}", status.error_message())};
 }