Keep implied target-cache values alive

... by uplinking them appropriately.

2 files changed, 23 insertions, 1 deletions

diff --git a/src/buildtool/storage/target_cache.hpp b/src/buildtool/storage/target_cache.hpp
index f263fdf9..385d1cd0 100644
--- a/src/buildtool/storage/target_cache.hpp
+++ b/src/buildtool/storage/target_cache.hpp
@@ -123,6 +123,11 @@ class TargetCache {
                 /*kSetEpochTime=*/false>
         file_store_;
 
+    template <bool kIsLocalGeneration = not kDoGlobalUplink>
+    requires(kIsLocalGeneration) [[nodiscard]] auto LocalUplinkEntry(
+        LocalGenerationTC const& latest,
+        std::string const& key_digest) const noexcept -> bool;
+
     [[nodiscard]] static auto ComputeShard() noexcept -> std::string {
         return ArtifactDigest::Create<ObjectType::File>(
                    StorageConfig::ExecutionBackendDescription())
diff --git a/src/buildtool/storage/target_cache.tpp b/src/buildtool/storage/target_cache.tpp
index d1c9d01c..cd56ef59 100644
--- a/src/buildtool/storage/target_cache.tpp
+++ b/src/buildtool/storage/target_cache.tpp
@@ -87,8 +87,15 @@ requires(kIsLocalGeneration) auto TargetCache<
     kDoGlobalUplink>::LocalUplinkEntry(LocalGenerationTC const& latest,
                                        TargetCacheKey const& key) const noexcept
     -> bool {
+    return LocalUplinkEntry(latest, key.Id().digest.hash());
+}
+
+template <bool kDoGlobalUplink>
+template <bool kIsLocalGeneration>
+requires(kIsLocalGeneration) auto TargetCache<kDoGlobalUplink>::
+    LocalUplinkEntry(LocalGenerationTC const& latest,
+                     std::string const& key_digest) const noexcept -> bool {
     // Determine target cache key path of given generation.
-    auto key_digest = key.Id().digest.hash();
     if (FileSystemManager::IsFile(latest.file_store_.GetPath(key_digest))) {
         return true;
     }
@@ -125,6 +132,16 @@ requires(kIsLocalGeneration) auto TargetCache<
         return false;
     }
     auto entry = TargetCacheEntry::FromJson(json_desc);
+
+    // Uplink the implied export targets first
+    for (auto const& implied_digest : entry.ToImplied()) {
+        if (implied_digest != key_digest) {
+            if (not LocalUplinkEntry(latest, implied_digest)) {
+                return false;
+            }
+        }
+    }
+
     std::vector<Artifact::ObjectInfo> artifacts_info;
     if (not entry.ToArtifacts(&artifacts_info)) {
         return false;