1 files changed, 13 insertions, 11 deletions

diff --git a/src/libstore/derived-path.cc b/src/libstore/derived-path.cc
index 88b59f615..3fa5ae4f7 100644
--- a/src/libstore/derived-path.cc
+++ b/src/libstore/derived-path.cc
@@ -20,11 +20,12 @@ nlohmann::json DerivedPath::Built::toJSON(ref<Store> store) const {
     // Fallback for the input-addressed derivation case: We expect to always be
     // able to print the output paths, so let’s do it
     const auto knownOutputs = store->queryPartialDerivationOutputMap(drvPath);
-    for (const auto& output : outputs) {
+    for (const auto & output : outputs) {
         auto knownOutput = get(knownOutputs, output);
-        res["outputs"][output] = (knownOutput && *knownOutput)
-          ? store->printStorePath(**knownOutput)
-          : nullptr;
+        if (knownOutput && *knownOutput)
+            res["outputs"][output] = store->printStorePath(**knownOutput);
+        else
+            res["outputs"][output] = nullptr;
     }
     return res;
 }
@@ -78,15 +79,16 @@ DerivedPath::Opaque DerivedPath::Opaque::parse(const Store & store, std::string_
     return {store.parseStorePath(s)};
 }
 
-DerivedPath::Built DerivedPath::Built::parse(const Store & store, std::string_view s)
+DerivedPath::Built DerivedPath::Built::parse(const Store & store, std::string_view drvS, std::string_view outputsS)
 {
-    size_t n = s.find("!");
-    assert(n != s.npos);
-    auto drvPath = store.parseStorePath(s.substr(0, n));
-    auto outputsS = s.substr(n + 1);
+    auto drvPath = store.parseStorePath(drvS);
     std::set<std::string> outputs;
-    if (outputsS != "*")
+    if (outputsS != "*") {
         outputs = tokenizeString<std::set<std::string>>(outputsS, ",");
+        if (outputs.empty())
+            throw Error(
+                 "Explicit list of wanted outputs '%s' must not be empty. Consider using '*' as a wildcard meaning all outputs if no output in particular is wanted.", outputsS);
+	}
     return {drvPath, outputs};
 }
 
@@ -95,7 +97,7 @@ DerivedPath DerivedPath::parse(const Store & store, std::string_view s)
     size_t n = s.find("!");
     return n == s.npos
         ? (DerivedPath) DerivedPath::Opaque::parse(store, s)
-        : (DerivedPath) DerivedPath::Built::parse(store, s);
+        : (DerivedPath) DerivedPath::Built::parse(store, s.substr(0, n), s.substr(n + 1));
 }
 
 RealisedPath::Set BuiltPath::toRealisedPaths(Store & store) const