3 files changed, 50 insertions, 24 deletions

diff --git a/src/libexpr/get-drvs.cc b/src/libexpr/get-drvs.cc
index 5d6e39aa0..d41cac132 100644
--- a/src/libexpr/get-drvs.cc
+++ b/src/libexpr/get-drvs.cc
@@ -39,7 +39,9 @@ DrvInfo::DrvInfo(EvalState & state, ref<Store> store, const std::string & drvPat
     if (i == drv.outputs.end())
         throw Error("derivation '%s' does not have output '%s'", store->printStorePath(drvPath), outputName);
 
-    outPath = store->printStorePath(i->second.path(*store, drv.name));
+    auto optStorePath = i->second.pathOpt(*store, drv.name);
+    if (optStorePath)
+        outPath = store->printStorePath(*optStorePath);
 }
 
 
@@ -77,12 +79,15 @@ string DrvInfo::queryDrvPath() const
 
 string DrvInfo::queryOutPath() const
 {
-    if (outPath == "" && attrs) {
+    if (!outPath && attrs) {
         Bindings::iterator i = attrs->find(state->sOutPath);
         PathSet context;
-        outPath = i != attrs->end() ? state->coerceToPath(*i->pos, *i->value, context) : "";
+        if (i != attrs->end())
+            outPath = state->coerceToPath(*i->pos, *i->value, context);
     }
-    return outPath;
+    if (!outPath)
+        throw UnimplementedError("CA derivations are not yet supported");
+    return *outPath;
 }
 
 
diff --git a/src/libexpr/get-drvs.hh b/src/libexpr/get-drvs.hh
index d7860fc6a..29bb6a660 100644
--- a/src/libexpr/get-drvs.hh
+++ b/src/libexpr/get-drvs.hh
@@ -20,7 +20,7 @@ private:
     mutable string name;
     mutable string system;
     mutable string drvPath;
-    mutable string outPath;
+    mutable std::optional<string> outPath;
     mutable string outputName;
     Outputs outputs;
 
diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index 65d36ca0e..11f44fb97 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -44,16 +44,6 @@ void EvalState::realiseContext(const PathSet & context)
             throw InvalidPathError(store->printStorePath(ctx));
         if (!outputName.empty() && ctx.isDerivation()) {
             drvs.push_back(StorePathWithOutputs{ctx, {outputName}});
-
-            /* Add the output of this derivation to the allowed
-               paths. */
-            if (allowedPaths) {
-                auto drv = store->derivationFromPath(ctx);
-                DerivationOutputs::iterator i = drv.outputs.find(outputName);
-                if (i == drv.outputs.end())
-                    throw Error("derivation '%s' does not have an output named '%s'", ctxS, outputName);
-                allowedPaths->insert(store->printStorePath(i->second.path(*store, drv.name)));
-            }
         }
     }
 
@@ -69,8 +59,38 @@ void EvalState::realiseContext(const PathSet & context)
     store->queryMissing(drvs, willBuild, willSubstitute, unknown, downloadSize, narSize);
 
     store->buildPaths(drvs);
+
+    /* Add the output of this derivations to the allowed
+       paths. */
+    if (allowedPaths) {
+        for (auto & [drvPath, outputs] : drvs) {
+            auto outputPaths = store->queryDerivationOutputMapAssumeTotal(drvPath);
+            for (auto & outputName : outputs) {
+                if (outputPaths.count(outputName) == 0)
+                    throw Error("derivation '%s' does not have an output named '%s'",
+                            store->printStorePath(drvPath), outputName);
+                allowedPaths->insert(store->printStorePath(outputPaths.at(outputName)));
+            }
+        }
+    }
 }
 
+static void mkOutputString(EvalState & state, Value & v,
+    const StorePath & drvPath, const BasicDerivation & drv,
+    std::pair<string, DerivationOutput> o)
+{
+    auto optOutputPath = o.second.pathOpt(*state.store, drv.name);
+    mkString(
+        *state.allocAttr(v, state.symbols.create(o.first)),
+        state.store->printStorePath(optOutputPath
+            ? *optOutputPath
+            /* Downstream we would substitute this for an actual path once
+               we build the floating CA derivation */
+            /* FIXME: we need to depend on the basic derivation, not
+               derivation */
+            : downstreamPlaceholder(*state.store, drvPath, o.first)),
+        {"!" + o.first + "!" + state.store->printStorePath(drvPath)});
+}
 
 /* Load and evaluate an expression from path specified by the
    argument. */
@@ -114,8 +134,7 @@ static void prim_scopedImport(EvalState & state, const Pos & pos, Value * * args
         unsigned int outputs_index = 0;
 
         for (const auto & o : drv.outputs) {
-            v2 = state.allocAttr(w, state.symbols.create(o.first));
-            mkString(*v2, state.store->printStorePath(o.second.path(*state.store, drv.name)), {"!" + o.first + "!" + path});
+            mkOutputString(state, w, storePath, drv, o);
             outputsVal->listElems()[outputs_index] = state.allocValue();
             mkString(*(outputsVal->listElems()[outputs_index++]), o.first);
         }
@@ -846,16 +865,18 @@ static void prim_derivationStrict(EvalState & state, const Pos & pos, Value * *
 
     /* Optimisation, but required in read-only mode! because in that
        case we don't actually write store derivations, so we can't
-       read them later. */
-    drvHashes.insert_or_assign(drvPath,
-        hashDerivationModulo(*state.store, Derivation(drv), false));
+       read them later.
+
+       However, we don't bother doing this for floating CA derivations because
+       their "hash modulo" is indeterminate until built. */
+    if (drv.type() != DerivationType::CAFloating)
+        drvHashes.insert_or_assign(drvPath,
+            hashDerivationModulo(*state.store, Derivation(drv), false));
 
     state.mkAttrs(v, 1 + drv.outputs.size());
     mkString(*state.allocAttr(v, state.sDrvPath), drvPathS, {"=" + drvPathS});
-    for (auto & i : drv.outputs) {
-        mkString(*state.allocAttr(v, state.symbols.create(i.first)),
-            state.store->printStorePath(i.second.path(*state.store, drv.name)), {"!" + i.first + "!" + drvPathS});
-    }
+    for (auto & i : drv.outputs)
+        mkOutputString(state, v, drvPath, drv, i);
     v.attrs->sort();
 }