Add --eval-store option

src/libcmd/command.cc

@@ -54,6 +54,38 @@ void StoreCommand::run()
     run(getStore());
 }
 
+EvalCommand::EvalCommand()
+{
+    // FIXME: move to MixEvalArgs?
+    addFlag({
+        .longName = "eval-store",
+        .description = "The Nix store to use for evaluations.",
+        .labels = {"store-url"},
+        //.category = ...,
+        .handler = {&evalStoreUrl},
+    });
+}
+
+EvalCommand::~EvalCommand()
+{
+    if (evalState)
+        evalState->printStats();
+}
+
+ref<Store> EvalCommand::getEvalStore()
+{
+    if (!evalStore)
+        evalStore = evalStoreUrl ? openStore(*evalStoreUrl) : getStore();
+    return ref<Store>(evalStore);
+}
+
+ref<EvalState> EvalCommand::getEvalState()
+{
+    if (!evalState)
+        evalState = std::make_shared<EvalState>(searchPath, getEvalStore(), getStore());
+    return ref<EvalState>(evalState);
+}
+
 BuiltPathsCommand::BuiltPathsCommand(bool recursive)
     : recursive(recursive)
 {

src/libcmd/command.hh

@@ -45,11 +45,20 @@ private:
 
 struct EvalCommand : virtual StoreCommand, MixEvalArgs
 {
-    ref<EvalState> getEvalState();
-
-    std::shared_ptr<EvalState> evalState;
+    EvalCommand();
 
     ~EvalCommand();
+
+    ref<Store> getEvalStore();
+
+    ref<EvalState> getEvalState();
+
+private:
+    std::optional<std::string> evalStoreUrl;
+
+    std::shared_ptr<Store> evalStore;
+
+    std::shared_ptr<EvalState> evalState;
 };
 
 struct MixFlakeOptions : virtual Args, EvalCommand

src/libcmd/installables.cc

@@ -289,19 +289,6 @@ void completeFlakeRefWithFragment(
     completeFlakeRef(evalState->store, prefix);
 }
 
-ref<EvalState> EvalCommand::getEvalState()
-{
-    if (!evalState)
-        evalState = std::make_shared<EvalState>(searchPath, getStore());
-    return ref<EvalState>(evalState);
-}
-
-EvalCommand::~EvalCommand()
-{
-    if (evalState)
-        evalState->printStats();
-}
-
 void completeFlakeRef(ref<Store> store, std::string_view prefix)
 {
     if (prefix == "")