Fix deadlock in IFD through the daemon

Fixes #4235.

src/libstore/derivations.cc

@@ -463,13 +463,15 @@ static const DrvHashModulo & pathDerivationModulo(Store & store, const StorePath
 {
     auto h = drvHashes.find(drvPath);
     if (h == drvHashes.end()) {
-        assert(store.isValidPath(drvPath));
         // Cache it
         h = drvHashes.insert_or_assign(
             drvPath,
             hashDerivationModulo(
                 store,
-                store.readDerivation(drvPath),
+                parseDerivation(
+                    store,
+                    readFile(store.toRealPath(drvPath)),
+                    Derivation::nameFromPath(drvPath)),
                 false)).first;
     }
     return h->second;

tests/remote-store.sh

@@ -7,6 +7,20 @@ nix --store ssh-ng://localhost?remote-store=$TEST_ROOT/other-store doctor
 
 startDaemon
 
+# Test import-from-derivation through the daemon.
+[[ $(nix eval --impure --raw --expr '
+  with import ./config.nix;
+  import (
+    mkDerivation {
+      name = "foo";
+      bla = import ./dependencies.nix;
+      buildCommand = "
+        echo \\\"hi\\\" > $out
+      ";
+    }
+  )
+') = hi ]]
+
 storeCleared=1 NIX_REMOTE_=$NIX_REMOTE $SHELL ./user-envs.sh
 
 nix-store --dump-db > $TEST_ROOT/d1