4 files changed, 43 insertions, 23 deletions
diff --git a/src/libstore/binary-cache-store.cc b/src/libstore/binary-cache-store.cc
index 12d0c32fb..14584f0a2 100644
--- a/src/libstore/binary-cache-store.cc
+++ b/src/libstore/binary-cache-store.cc
@@ -504,18 +504,10 @@ void BinaryCacheStore::addSignatures(const StorePath & storePath, const StringSe
 
 std::optional<std::string> BinaryCacheStore::getBuildLog(const StorePath & path)
 {
-    auto drvPath = path;
-
-    if (!path.isDerivation()) {
-        try {
-            auto info = queryPathInfo(path);
-            // FIXME: add a "Log" field to .narinfo
-            if (!info->deriver) return std::nullopt;
-            drvPath = *info->deriver;
-        } catch (InvalidPath &) {
-            return std::nullopt;
-        }
-    }
+    auto maybePath = getBuildDerivationPath(path);
+    if (!maybePath)
+        return std::nullopt;
+    auto drvPath = maybePath.value();
 
     auto logPath = "log/" + std::string(baseNameOf(printStorePath(drvPath)));
 
diff --git a/src/libstore/local-fs-store.cc b/src/libstore/local-fs-store.cc
index c5ae7536f..3a0585b15 100644
--- a/src/libstore/local-fs-store.cc
+++ b/src/libstore/local-fs-store.cc
@@ -89,17 +89,10 @@ const std::string LocalFSStore::drvsLogDir = "drvs";
 
 std::optional<std::string> LocalFSStore::getBuildLog(const StorePath & path_)
 {
-    auto path = path_;
-
-    if (!path.isDerivation()) {
-        try {
-            auto info = queryPathInfo(path);
-            if (!info->deriver) return std::nullopt;
-            path = *info->deriver;
-        } catch (InvalidPath &) {
-            return std::nullopt;
-        }
-    }
+    auto maybePath = getBuildDerivationPath(path_);
+    if (!maybePath)
+        return std::nullopt;
+    auto path = maybePath.value();
 
     auto baseName = path.to_string();
 
diff --git a/src/libstore/store-api.cc b/src/libstore/store-api.cc
index 8811ab578..ebd641aa4 100644
--- a/src/libstore/store-api.cc
+++ b/src/libstore/store-api.cc
@@ -1300,6 +1300,34 @@ Derivation readDerivationCommon(Store& store, const StorePath& drvPath, bool req
     }
 }
 
+std::optional<StorePath> Store::getBuildDerivationPath(const StorePath & path)
+{
+
+    if (!path.isDerivation()) {
+        try {
+            auto info = queryPathInfo(path);
+            if (!info->deriver) return std::nullopt;
+            return *info->deriver;
+        } catch (InvalidPath &) {
+            return std::nullopt;
+        }
+    }
+
+    if (!settings.isExperimentalFeatureEnabled(Xp::CaDerivations) || !isValidPath(path))
+        return path;
+
+    auto drv = readDerivation(path);
+    if (!derivationHasKnownOutputPaths(drv.type())) {
+        // The build log is actually attached to the corresponding
+        // resolved derivation, so we need to get it first
+        auto resolvedDrv = drv.tryResolve(*this);
+        if (resolvedDrv)
+            return writeDerivation(*this, *resolvedDrv, NoRepair, true);
+    }
+
+    return path;
+}
+
 Derivation Store::readDerivation(const StorePath & drvPath)
 { return readDerivationCommon(*this, drvPath, true); }
 
diff --git a/src/libstore/store-api.hh b/src/libstore/store-api.hh
index 151ec10d6..88a11d953 100644
--- a/src/libstore/store-api.hh
+++ b/src/libstore/store-api.hh
@@ -618,6 +618,13 @@ public:
      */
     StorePathSet exportReferences(const StorePathSet & storePaths, const StorePathSet & inputPaths);
 
+    /**
+     * Given a store path, return the realisation actually used in the realisation of this path:
+     * - If the path is a content-addressed derivation, try to resolve it
+     * - Otherwise, find one of its derivers
+     */
+    std::optional<StorePath> getBuildDerivationPath(const StorePath &);
+
     /* Hack to allow long-running processes like hydra-queue-runner to
        occasionally flush their path info cache. */
     void clearPathInfoCache()