1 files changed, 14 insertions, 5 deletions

diff --git a/src/libstore/download.cc b/src/libstore/download.cc
index 149c84765..8e0d7d42a 100644
--- a/src/libstore/download.cc
+++ b/src/libstore/download.cc
@@ -819,6 +819,7 @@ CachedDownloadResult Downloader::downloadCached(
             CachedDownloadResult result;
             result.storePath = store->printStorePath(*expectedStorePath);
             result.path = store->toRealPath(result.storePath);
+            assert(!request.getLastModified); // FIXME
             return result;
         }
     }
@@ -900,35 +901,43 @@ CachedDownloadResult Downloader::downloadCached(
         std::optional<StorePath> unpackedStorePath;
         if (pathExists(unpackedLink)) {
             unpackedStorePath = store->parseStorePath(readLink(unpackedLink));
-            // FIXME
             store->addTempRoot(*unpackedStorePath);
             if (!store->isValidPath(*unpackedStorePath))
                 unpackedStorePath.reset();
+            else
+                result.lastModified = lstat(unpackedLink).st_mtime;
         }
         if (!unpackedStorePath) {
             printInfo("unpacking '%s'...", url);
             Path tmpDir = createTempDir();
             AutoDelete autoDelete(tmpDir, true);
-            unpackTarfile(store->toRealPath(store->printStorePath(*storePath)), tmpDir);
+            unpackTarfile(store->toRealPath(*storePath), tmpDir);
             auto members = readDirectory(tmpDir);
             if (members.size() != 1)
                 throw nix::Error("tarball '%s' contains an unexpected number of top-level files", url);
             auto topDir = tmpDir + "/" + members.begin()->name;
+            result.lastModified = lstat(topDir).st_mtime;
             unpackedStorePath = store->addToStore(name, topDir, true, htSHA256, defaultPathFilter, NoRepair);
         }
-        replaceSymlink(store->printStorePath(*unpackedStorePath), unpackedLink);
+        // Store the last-modified date of the tarball in the symlink
+        // mtime. This saves us from having to store it somewhere
+        // else.
+        replaceSymlink(store->printStorePath(*unpackedStorePath), unpackedLink, result.lastModified);
         storePath = std::move(*unpackedStorePath);
     }
 
     if (expectedStorePath && *storePath != *expectedStorePath) {
         unsigned int statusCode = 102;
         Hash gotHash = request.unpack
-            ? hashPath(request.expectedHash.type, store->toRealPath(store->printStorePath(*storePath))).first
-            : hashFile(request.expectedHash.type, store->toRealPath(store->printStorePath(*storePath)));
+            ? hashPath(request.expectedHash.type, store->toRealPath(*storePath)).first
+            : hashFile(request.expectedHash.type, store->toRealPath(*storePath));
         throw nix::Error(statusCode, "hash mismatch in file downloaded from '%s':\n  wanted: %s\n  got:    %s",
             url, request.expectedHash.to_string(), gotHash.to_string());
     }
 
+    if (request.gcRoot)
+        store->addIndirectRoot(fileLink);
+
     result.storePath = store->printStorePath(*storePath);
     result.path = store->toRealPath(result.storePath);
     return result;