Make the JSON format for derivation use basename store paths

See #13570 for details --- the idea is that included the store dir in
store paths makes systematic JSON parting with e.g. Serde, Aeson,
nlohmann, or similiar harder.

After talking to Eelco, we are changing the `Derivation` format right
away because not only is `nix derivation` technically experimental, we think it is
also less widely used in practice than, say, `nix path-info`.

Progress on #13570

src/libstore/derivations.cc

@@ -1257,15 +1257,14 @@ void Derivation::checkInvariants(Store & store, const StorePath & drvPath) const
 
 const Hash impureOutputHash = hashString(HashAlgorithm::SHA256, "impure");
 
-nlohmann::json
-DerivationOutput::toJSON(const StoreDirConfig & store, std::string_view drvName, OutputNameView outputName) const
+nlohmann::json DerivationOutput::toJSON(std::string_view drvName, OutputNameView outputName) const
 {
     nlohmann::json res = nlohmann::json::object();
     std::visit(
         overloaded{
-            [&](const DerivationOutput::InputAddressed & doi) { res["path"] = store.printStorePath(doi.path); },
+            [&](const DerivationOutput::InputAddressed & doi) { res["path"] = doi.path; },
             [&](const DerivationOutput::CAFixed & dof) {
-                res["path"] = store.printStorePath(dof.path(store, drvName, outputName));
+                // res["path"] = dof.path(store, drvName, outputName);
                 res["method"] = std::string{dof.ca.method.render()};
                 res["hashAlgo"] = printHashAlgo(dof.ca.hash.algo);
                 res["hash"] = dof.ca.hash.to_string(HashFormat::Base16, false);
@@ -1287,7 +1286,6 @@ DerivationOutput::toJSON(const StoreDirConfig & store, std::string_view drvName,
 }
 
 DerivationOutput DerivationOutput::fromJSON(
-    const StoreDirConfig & store,
     std::string_view drvName,
     OutputNameView outputName,
     const nlohmann::json & _json,
@@ -1310,11 +1308,11 @@ DerivationOutput DerivationOutput::fromJSON(
 
     if (keys == (std::set<std::string_view>{"path"})) {
         return DerivationOutput::InputAddressed{
-            .path = store.parseStorePath(getString(valueAt(json, "path"))),
+            .path = valueAt(json, "path"),
         };
     }
 
-    else if (keys == (std::set<std::string_view>{"path", "method", "hashAlgo", "hash"})) {
+    else if (keys == (std::set<std::string_view>{"method", "hashAlgo", "hash"})) {
         auto [method, hashAlgo] = methodAlgo();
         auto dof = DerivationOutput::CAFixed{
             .ca =
@@ -1323,8 +1321,10 @@ DerivationOutput DerivationOutput::fromJSON(
                     .hash = Hash::parseNonSRIUnprefixed(getString(valueAt(json, "hash")), hashAlgo),
                 },
         };
-        if (dof.path(store, drvName, outputName) != store.parseStorePath(getString(valueAt(json, "path"))))
+#if 0
+        if (dof.path(store, drvName, outputName) != static_cast<StorePath>(valueAt(json, "path")))
             throw Error("Path doesn't match derivation output");
+#endif
         return dof;
     }
 
@@ -1355,17 +1355,19 @@ DerivationOutput DerivationOutput::fromJSON(
     }
 }
 
-nlohmann::json Derivation::toJSON(const StoreDirConfig & store) const
+nlohmann::json Derivation::toJSON() const
 {
     nlohmann::json res = nlohmann::json::object();
 
     res["name"] = name;
 
+    res["version"] = 3;
+
     {
         nlohmann::json & outputsObj = res["outputs"];
         outputsObj = nlohmann::json::object();
         for (auto & [outputName, output] : outputs) {
-            outputsObj[outputName] = output.toJSON(store, name, outputName);
+            outputsObj[outputName] = output.toJSON(name, outputName);
         }
     }
 
@@ -1373,7 +1375,7 @@ nlohmann::json Derivation::toJSON(const StoreDirConfig & store) const
         auto & inputsList = res["inputSrcs"];
         inputsList = nlohmann::json ::array();
         for (auto & input : inputSrcs)
-            inputsList.emplace_back(store.printStorePath(input));
+            inputsList.emplace_back(input);
     }
 
     {
@@ -1393,7 +1395,7 @@ nlohmann::json Derivation::toJSON(const StoreDirConfig & store) const
             auto & inputDrvsObj = res["inputDrvs"];
             inputDrvsObj = nlohmann::json::object();
             for (auto & [inputDrv, inputNode] : inputDrvs.map) {
-                inputDrvsObj[store.printStorePath(inputDrv)] = doInput(inputNode);
+                inputDrvsObj[inputDrv.to_string()] = doInput(inputNode);
             }
         }
     }
@@ -1409,8 +1411,7 @@ nlohmann::json Derivation::toJSON(const StoreDirConfig & store) const
     return res;
 }
 
-Derivation Derivation::fromJSON(
-    const StoreDirConfig & store, const nlohmann::json & _json, const ExperimentalFeatureSettings & xpSettings)
+Derivation Derivation::fromJSON(const nlohmann::json & _json, const ExperimentalFeatureSettings & xpSettings)
 {
     using nlohmann::detail::value_t;
 
@@ -1420,11 +1421,14 @@ Derivation Derivation::fromJSON(
 
     res.name = getString(valueAt(json, "name"));
 
+    if (valueAt(json, "version") != 3)
+        throw Error("Only derivation format version 3 is currently supported.");
+
     try {
         auto outputs = getObject(valueAt(json, "outputs"));
         for (auto & [outputName, output] : outputs) {
             res.outputs.insert_or_assign(
-                outputName, DerivationOutput::fromJSON(store, res.name, outputName, output, xpSettings));
+                outputName, DerivationOutput::fromJSON(res.name, outputName, output, xpSettings));
         }
     } catch (Error & e) {
         e.addTrace({}, "while reading key 'outputs'");
@@ -1434,7 +1438,7 @@ Derivation Derivation::fromJSON(
     try {
         auto inputSrcs = getArray(valueAt(json, "inputSrcs"));
         for (auto & input : inputSrcs)
-            res.inputSrcs.insert(store.parseStorePath(static_cast<const std::string &>(input)));
+            res.inputSrcs.insert(input);
     } catch (Error & e) {
         e.addTrace({}, "while reading key 'inputSrcs'");
         throw;
@@ -1455,7 +1459,7 @@ Derivation Derivation::fromJSON(
         };
         auto drvs = getObject(valueAt(json, "inputDrvs"));
         for (auto & [inputDrvPath, inputOutputs] : drvs)
-            res.inputDrvs.map[store.parseStorePath(inputDrvPath)] = doInput(inputOutputs);
+            res.inputDrvs.map[StorePath{inputDrvPath}] = doInput(inputOutputs);
     } catch (Error & e) {
         e.addTrace({}, "while reading key 'inputDrvs'");
         throw;
@@ -1480,3 +1484,19 @@ Derivation Derivation::fromJSON(
 }
 
 } // namespace nix
+
+namespace nlohmann {
+
+using namespace nix;
+
+Derivation adl_serializer<Derivation>::from_json(const json & json)
+{
+    return Derivation::fromJSON(json);
+}
+
+void adl_serializer<Derivation>::to_json(json & json, Derivation c)
+{
+    json = c.toJSON();
+}
+
+} // namespace nlohmann

src/libstore/include/nix/store/derivations.hh

@@ -135,12 +135,11 @@ struct DerivationOutput
     std::optional<StorePath>
     path(const StoreDirConfig & store, std::string_view drvName, OutputNameView outputName) const;
 
-    nlohmann::json toJSON(const StoreDirConfig & store, std::string_view drvName, OutputNameView outputName) const;
+    nlohmann::json toJSON(std::string_view drvName, OutputNameView outputName) const;
     /**
      * @param xpSettings Stop-gap to avoid globals during unit tests.
      */
     static DerivationOutput fromJSON(
-        const StoreDirConfig & store,
         std::string_view drvName,
         OutputNameView outputName,
         const nlohmann::json & json,
@@ -394,11 +393,9 @@ struct Derivation : BasicDerivation
     {
     }
 
-    nlohmann::json toJSON(const StoreDirConfig & store) const;
-    static Derivation fromJSON(
-        const StoreDirConfig & store,
-        const nlohmann::json & json,
-        const ExperimentalFeatureSettings & xpSettings = experimentalFeatureSettings);
+    nlohmann::json toJSON() const;
+    static Derivation
+    fromJSON(const nlohmann::json & json, const ExperimentalFeatureSettings & xpSettings = experimentalFeatureSettings);
 
     bool operator==(const Derivation &) const = default;
     // TODO libc++ 16 (used by darwin) missing `std::map::operator <=>`, can't do yet.
@@ -542,3 +539,5 @@ void writeDerivation(Sink & out, const StoreDirConfig & store, const BasicDeriva
 std::string hashPlaceholder(const OutputNameView outputName);
 
 } // namespace nix
+
+JSON_IMPL(nix::Derivation)

src/libstore/include/nix/store/path.hh

@@ -4,6 +4,8 @@
 #include <string_view>
 
 #include "nix/util/types.hh"
+#include "nix/util/json-impls.hh"
+#include "nix/util/json-non-null.hh"
 
 namespace nix {
 
@@ -87,6 +89,10 @@ typedef std::vector<StorePath> StorePaths;
  */
 constexpr std::string_view drvExtension = ".drv";
 
+template<>
+struct json_avoids_null<StorePath> : std::true_type
+{};
+
 } // namespace nix
 
 namespace std {
@@ -101,3 +107,5 @@ struct hash<nix::StorePath>
 };
 
 } // namespace std
+
+JSON_IMPL(nix::StorePath)

src/libstore/path.cc

@@ -1,4 +1,7 @@
+#include <nlohmann/json.hpp>
+
 #include "nix/store/store-dir-config.hh"
+#include "nix/util/json-utils.hh"
 
 namespace nix {
 
@@ -75,3 +78,19 @@ StorePath StorePath::random(std::string_view name)
 }
 
 } // namespace nix
+
+namespace nlohmann {
+
+using namespace nix;
+
+StorePath adl_serializer<StorePath>::from_json(const json & json)
+{
+    return StorePath{getString(json)};
+}
+
+void adl_serializer<StorePath>::to_json(json & json, StorePath storePath)
+{
+    json = storePath.to_string();
+}
+
+} // namespace nlohmann