2 files changed, 52 insertions, 2 deletions

diff --git a/src/libstore/path-with-outputs.cc b/src/libstore/path-with-outputs.cc
index 7d180a0f6..d6d67ea05 100644
--- a/src/libstore/path-with-outputs.cc
+++ b/src/libstore/path-with-outputs.cc
@@ -1,5 +1,6 @@
 #include "path-with-outputs.hh"
 #include "store-api.hh"
+#include "nlohmann/json.hpp"
 
 #include <regex>
 
@@ -84,4 +85,43 @@ std::pair<std::string, OutputsSpec> parseOutputsSpec(const std::string & s)
     return {match[1], tokenizeString<OutputNames>(match[4].str(), ",")};
 }
 
+std::string printOutputsSpec(const OutputsSpec & outputsSpec)
+{
+    if (std::get_if<DefaultOutputs>(&outputsSpec))
+        return "";
+
+    if (std::get_if<AllOutputs>(&outputsSpec))
+        return "^*";
+
+    if (auto outputNames = std::get_if<OutputNames>(&outputsSpec))
+        return "^" + concatStringsSep(",", *outputNames);
+
+    assert(false);
+}
+
+void to_json(nlohmann::json & json, const OutputsSpec & outputsSpec)
+{
+    if (std::get_if<DefaultOutputs>(&outputsSpec))
+        json = nullptr;
+
+    else if (std::get_if<AllOutputs>(&outputsSpec))
+        json = std::vector<std::string>({"*"});
+
+    else if (auto outputNames = std::get_if<OutputNames>(&outputsSpec))
+        json = *outputNames;
+}
+
+void from_json(const nlohmann::json & json, OutputsSpec & outputsSpec)
+{
+    if (json.is_null())
+        outputsSpec = DefaultOutputs();
+    else {
+        auto names = json.get<OutputNames>();
+        if (names == OutputNames({"*"}))
+            outputsSpec = AllOutputs();
+        else
+            outputsSpec = names;
+    }
+}
+
 }
diff --git a/src/libstore/path-with-outputs.hh b/src/libstore/path-with-outputs.hh
index e4235d197..0cb5eb223 100644
--- a/src/libstore/path-with-outputs.hh
+++ b/src/libstore/path-with-outputs.hh
@@ -4,6 +4,7 @@
 
 #include "path.hh"
 #include "derived-path.hh"
+#include "nlohmann/json_fwd.hpp"
 
 namespace nix {
 
@@ -34,9 +35,13 @@ StorePathWithOutputs followLinksToStorePathWithOutputs(const Store & store, std:
 
 typedef std::set<std::string> OutputNames;
 
-struct AllOutputs { };
+struct AllOutputs {
+    bool operator < (const AllOutputs & _) const { return false; }
+};
 
-struct DefaultOutputs { };
+struct DefaultOutputs {
+    bool operator < (const DefaultOutputs & _) const { return false; }
+};
 
 typedef std::variant<DefaultOutputs, AllOutputs, OutputNames> OutputsSpec;
 
@@ -44,4 +49,9 @@ typedef std::variant<DefaultOutputs, AllOutputs, OutputNames> OutputsSpec;
    'prefix^*', returning the prefix and the outputs spec. */
 std::pair<std::string, OutputsSpec> parseOutputsSpec(const std::string & s);
 
+std::string printOutputsSpec(const OutputsSpec & outputsSpec);
+
+void to_json(nlohmann::json &, const OutputsSpec &);
+void from_json(const nlohmann::json &, OutputsSpec &);
+
 }