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-rw-r--r--src/libstore/remote-store.cc14
-rw-r--r--src/libstore/worker-protocol.hh7
2 files changed, 21 insertions, 0 deletions
diff --git a/src/libstore/remote-store.cc b/src/libstore/remote-store.cc
index 96e0aabba..005415666 100644
--- a/src/libstore/remote-store.cc
+++ b/src/libstore/remote-store.cc
@@ -70,6 +70,20 @@ void write(const Store & store, Sink & out, const StorePath & storePath)
out << store.printStorePath(storePath);
}
+
+template<>
+std::optional<StorePath> read(const Store & store, Source & from, Phantom<std::optional<StorePath>> _)
+{
+ auto s = readString(from);
+ return s == "" ? std::optional<StorePath> {} : store.parseStorePath(s);
+}
+
+template<>
+void write(const Store & store, Sink & out, const std::optional<StorePath> & storePathOpt)
+{
+ out << (storePathOpt ? store.printStorePath(*storePathOpt) : "");
+}
+
}
diff --git a/src/libstore/worker-protocol.hh b/src/libstore/worker-protocol.hh
index c50995d7c..b3576fbeb 100644
--- a/src/libstore/worker-protocol.hh
+++ b/src/libstore/worker-protocol.hh
@@ -90,6 +90,13 @@ std::optional<T> read(const Store & store, Source & from, Phantom<std::optional<
template<typename T>
void write(const Store & store, Sink & out, const std::optional<T> & optVal);
+/* Specialization which uses and empty string for the empty case, taking
+ advantage of the fact StorePaths always serialize to a non-empty string.
+ This is done primarily for backwards compatability, so that StorePath <=
+ std::optional<StorePath>, where <= is the compatability partial order.
+ */
+template<>
+void write(const Store & store, Sink & out, const std::optional<StorePath> & optVal);
template<typename T>
std::map<std::string, T> read(const Store & store, Source & from, Phantom<std::map<std::string, T>> _)