From a291e37b20efa54c6a5f3394a01dfc42881b0478 Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <edolstra@gmail.com>
Date: Wed, 28 Sep 2022 15:09:24 +0200
Subject: [PATCH] Improve error messages from call-flake.nix

---
 src/libexpr/eval.cc        |  6 ++++++
 src/libexpr/eval.hh        |  4 +++-
 src/libexpr/flake/flake.cc | 10 +++-------
 3 files changed, 12 insertions(+), 8 deletions(-)

diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 9ec6b04c6..bfe6c01dd 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -477,10 +477,15 @@ EvalState::EvalState(
                 throw RestrictedPathError("access to absolute path '%1%' is forbidden %2%", path, modeInformation);
             }))
     , corepkgsFS(makeMemoryInputAccessor())
+    , internalFS(makeMemoryInputAccessor())
     , derivationInternal{corepkgsFS->addFile(
         CanonPath("derivation-internal.nix"),
         #include "primops/derivation.nix.gen.hh"
     )}
+    , callFlakeInternal{internalFS->addFile(
+        CanonPath("call-flake.nix"),
+        #include "flake/call-flake.nix.gen.hh"
+    )}
     , store(store)
     , buildStore(buildStore ? buildStore : store)
     , debugRepl(nullptr)
@@ -499,6 +504,7 @@ EvalState::EvalState(
     , staticBaseEnv{std::make_shared<StaticEnv>(false, nullptr)}
 {
     corepkgsFS->setPathDisplay("<nix", ">");
+    internalFS->setPathDisplay("«nix-internal»", "");
 
     countCalls = getEnv("NIX_COUNT_CALLS").value_or("0") != "0";
 
diff --git a/src/libexpr/eval.hh b/src/libexpr/eval.hh
index 390b79617..2fb6a74c9 100644
--- a/src/libexpr/eval.hh
+++ b/src/libexpr/eval.hh
@@ -111,9 +111,12 @@ public:
 
     const ref<FSInputAccessor> rootFS;
     const ref<MemoryInputAccessor> corepkgsFS;
+    const ref<MemoryInputAccessor> internalFS;
 
     const SourcePath derivationInternal;
 
+    const SourcePath callFlakeInternal;
+
     /* A map keyed by InputAccessor::number that keeps input accessors
        alive. */
     std::unordered_map<size_t, ref<InputAccessor>> inputAccessors;
@@ -124,7 +127,6 @@ public:
     /* Store used to build stuff. */
     const ref<Store> buildStore;
 
-    RootValue vCallFlake = nullptr;
     RootValue vImportedDrvToDerivation = nullptr;
 
     /* Debugger */
diff --git a/src/libexpr/flake/flake.cc b/src/libexpr/flake/flake.cc
index 07fb75fd5..82adda4a7 100644
--- a/src/libexpr/flake/flake.cc
+++ b/src/libexpr/flake/flake.cc
@@ -704,14 +704,10 @@ void callFlake(EvalState & state,
 
     vRootSubdir->mkString(lockedFlake.flake.lockedRef.subdir);
 
-    if (!state.vCallFlake) {
-        state.vCallFlake = allocRootValue(state.allocValue());
-        state.eval(state.parseExprFromString(
-            #include "call-flake.nix.gen.hh"
-            , state.rootPath("/")), **state.vCallFlake);
-    }
+    Value vCallFlake;
+    state.evalFile(state.callFlakeInternal, vCallFlake);
 
-    state.callFunction(**state.vCallFlake, *vLocks, *vTmp1, noPos);
+    state.callFunction(vCallFlake, *vLocks, *vTmp1, noPos);
     state.callFunction(*vTmp1, *vRootSrc, *vTmp2, noPos);
     state.callFunction(*vTmp2, *vRootSubdir, vRes, noPos);
 }