5 files changed, 52 insertions, 22 deletions

diff --git a/src/libstore/build/local-derivation-goal.cc b/src/libstore/build/local-derivation-goal.cc
index b7a27490c..8b7fbdcda 100644
--- a/src/libstore/build/local-derivation-goal.cc
+++ b/src/libstore/build/local-derivation-goal.cc
@@ -2307,7 +2307,6 @@ SingleDrvOutputs LocalDerivationGoal::registerOutputs()
         bool discardReferences = false;
         if (auto structuredAttrs = parsedDrv->getStructuredAttrs()) {
             if (auto udr = get(*structuredAttrs, "unsafeDiscardReferences")) {
-                experimentalFeatureSettings.require(Xp::DiscardReferences);
                 if (auto output = get(*udr, outputName)) {
                     if (!output->is_boolean())
                         throw Error("attribute 'unsafeDiscardReferences.\"%s\"' of derivation '%s' must be a Boolean", outputName, drvPath.to_string());
diff --git a/src/libstore/derivations.cc b/src/libstore/derivations.cc
index b831b2fe5..f4e4980c2 100644
--- a/src/libstore/derivations.cc
+++ b/src/libstore/derivations.cc
@@ -879,9 +879,11 @@ std::optional<BasicDerivation> Derivation::tryResolve(
     for (auto & [inputDrv, inputOutputs] : inputDrvs) {
         for (auto & outputName : inputOutputs) {
             if (auto actualPath = get(inputDrvOutputs, { inputDrv, outputName })) {
-                inputRewrites.emplace(
-                    DownstreamPlaceholder::unknownCaOutput(inputDrv, outputName).render(),
-                    store.printStorePath(*actualPath));
+                if (experimentalFeatureSettings.isEnabled(Xp::CaDerivations)) {
+                    inputRewrites.emplace(
+                        DownstreamPlaceholder::unknownCaOutput(inputDrv, outputName).render(),
+                        store.printStorePath(*actualPath));
+                }
                 resolved.inputSrcs.insert(*actualPath);
             } else {
                 warn("output '%s' of input '%s' missing, aborting the resolving",
@@ -993,6 +995,7 @@ DerivationOutput DerivationOutput::fromJSON(
     const ExperimentalFeatureSettings & xpSettings)
 {
     std::set<std::string_view> keys;
+    ensureType(_json, nlohmann::detail::value_t::object);
     auto json = (std::map<std::string, nlohmann::json>) _json;
 
     for (const auto & [key, _] : json)
@@ -1097,36 +1100,51 @@ Derivation Derivation::fromJSON(
     const Store & store,
     const nlohmann::json & json)
 {
+    using nlohmann::detail::value_t;
+
     Derivation res;
 
-    res.name = json["name"];
+    ensureType(json, value_t::object);
 
-    {
-        auto & outputsObj = json["outputs"];
+    res.name = ensureType(valueAt(json, "name"), value_t::string);
+
+    try {
+        auto & outputsObj = ensureType(valueAt(json, "outputs"), value_t::object);
         for (auto & [outputName, output] : outputsObj.items()) {
             res.outputs.insert_or_assign(
                 outputName,
                 DerivationOutput::fromJSON(store, res.name, outputName, output));
         }
+    } catch (Error & e) {
+        e.addTrace({}, "while reading key 'outputs'");
+        throw;
     }
 
-    {
-        auto & inputsList = json["inputSrcs"];
+    try {
+        auto & inputsList = ensureType(valueAt(json, "inputSrcs"), value_t::array);
         for (auto & input : inputsList)
             res.inputSrcs.insert(store.parseStorePath(static_cast<const std::string &>(input)));
+    } catch (Error & e) {
+        e.addTrace({}, "while reading key 'inputSrcs'");
+        throw;
     }
 
-    {
-        auto & inputDrvsObj = json["inputDrvs"];
-        for (auto & [inputDrvPath, inputOutputs] : inputDrvsObj.items())
+    try {
+        auto & inputDrvsObj = ensureType(valueAt(json, "inputDrvs"), value_t::object);
+        for (auto & [inputDrvPath, inputOutputs] : inputDrvsObj.items()) {
+            ensureType(inputOutputs, value_t::array);
             res.inputDrvs[store.parseStorePath(inputDrvPath)] =
                 static_cast<const StringSet &>(inputOutputs);
+        }
+    } catch (Error & e) {
+        e.addTrace({}, "while reading key 'inputDrvs'");
+        throw;
     }
 
-    res.platform = json["system"];
-    res.builder = json["builder"];
-    res.args = json["args"];
-    res.env = json["env"];
+    res.platform = ensureType(valueAt(json, "system"), value_t::string);
+    res.builder = ensureType(valueAt(json, "builder"), value_t::string);
+    res.args = ensureType(valueAt(json, "args"), value_t::array);
+    res.env = ensureType(valueAt(json, "env"), value_t::object);
 
     return res;
 }
diff --git a/src/libstore/downstream-placeholder.cc b/src/libstore/downstream-placeholder.cc
index 1752738f2..d623c05e2 100644
--- a/src/libstore/downstream-placeholder.cc
+++ b/src/libstore/downstream-placeholder.cc
@@ -11,8 +11,10 @@ std::string DownstreamPlaceholder::render() const
 
 DownstreamPlaceholder DownstreamPlaceholder::unknownCaOutput(
     const StorePath & drvPath,
-    std::string_view outputName)
+    std::string_view outputName,
+    const ExperimentalFeatureSettings & xpSettings)
 {
+    xpSettings.require(Xp::CaDerivations);
     auto drvNameWithExtension = drvPath.name();
     auto drvName = drvNameWithExtension.substr(0, drvNameWithExtension.size() - 4);
     auto clearText = "nix-upstream-output:" + std::string { drvPath.hashPart() } + ":" + outputPathName(drvName, outputName);
diff --git a/src/libstore/downstream-placeholder.hh b/src/libstore/downstream-placeholder.hh
index f0c0dee77..97f77e6b8 100644
--- a/src/libstore/downstream-placeholder.hh
+++ b/src/libstore/downstream-placeholder.hh
@@ -52,10 +52,13 @@ public:
      *
      * The derivation itself is known (we have a store path for it), but
      * the output doesn't yet have a known store path.
+     *
+     * @param xpSettings Stop-gap to avoid globals during unit tests.
      */
     static DownstreamPlaceholder unknownCaOutput(
         const StorePath & drvPath,
-        std::string_view outputName);
+        std::string_view outputName,
+        const ExperimentalFeatureSettings & xpSettings = experimentalFeatureSettings);
 
     /**
      * Create a placehold for the output of an unknown derivation.
diff --git a/src/libstore/tests/downstream-placeholder.cc b/src/libstore/tests/downstream-placeholder.cc
index ec3e1000f..fd29530ac 100644
--- a/src/libstore/tests/downstream-placeholder.cc
+++ b/src/libstore/tests/downstream-placeholder.cc
@@ -5,17 +5,24 @@
 namespace nix {
 
 TEST(DownstreamPlaceholder, unknownCaOutput) {
+    /**
+     * We set these in tests rather than the regular globals so we don't have
+     * to worry about race conditions if the tests run concurrently.
+     */
+    ExperimentalFeatureSettings mockXpSettings;
+    mockXpSettings.set("experimental-features", "ca-derivations");
+
     ASSERT_EQ(
         DownstreamPlaceholder::unknownCaOutput(
             StorePath { "g1w7hy3qg1w7hy3qg1w7hy3qg1w7hy3q-foo.drv" },
-            "out").render(),
+            "out",
+            mockXpSettings).render(),
         "/0c6rn30q4frawknapgwq386zq358m8r6msvywcvc89n6m5p2dgbz");
 }
 
 TEST(DownstreamPlaceholder, unknownDerivation) {
     /**
-     * We set these in tests rather than the regular globals so we don't have
-     * to worry about race conditions if the tests run concurrently.
+     * Same reason as above
      */
     ExperimentalFeatureSettings mockXpSettings;
     mockXpSettings.set("experimental-features", "dynamic-derivations ca-derivations");
@@ -24,7 +31,8 @@ TEST(DownstreamPlaceholder, unknownDerivation) {
         DownstreamPlaceholder::unknownDerivation(
             DownstreamPlaceholder::unknownCaOutput(
                 StorePath { "g1w7hy3qg1w7hy3qg1w7hy3qg1w7hy3q-foo.drv.drv" },
-                "out"),
+                "out",
+                mockXpSettings),
             "out",
             mockXpSettings).render(),
         "/0gn6agqxjyyalf0dpihgyf49xq5hqxgw100f0wydnj6yqrhqsb3w");