From 78232889c0340f23836ac44dc62cab63eeb4e42e Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <edolstra@gmail.com>
Date: Thu, 7 Jul 2022 14:29:58 +0200
Subject: [PATCH] Use corepkgsFS for derivation.nix

---
 src/libexpr/eval.cc               | 20 +++++++++++++-------
 src/libexpr/eval.hh               |  9 ++++-----
 src/libexpr/primops.cc            |  9 +--------
 src/libfetchers/input-accessor.cc |  6 ++++--
 src/libfetchers/input-accessor.hh |  4 +++-
 5 files changed, 25 insertions(+), 23 deletions(-)

diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 497a1e8f5..cf90d1da6 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -475,6 +475,10 @@ EvalState::EvalState(
                 throw RestrictedPathError("access to absolute path '%1%' is forbidden %2%", path, modeInformation);
             }))
     , corepkgsFS(makeMemoryInputAccessor())
+    , derivationInternal{corepkgsFS->addFile(
+        CanonPath("derivation-internal.nix"),
+        #include "primops/derivation.nix.gen.hh"
+    )}
     , store(store)
     , buildStore(buildStore ? buildStore : store)
     , debugRepl(0)
@@ -508,12 +512,12 @@ EvalState::EvalState(
         for (auto & i : searchPath)
             resolveSearchPathElem(i, true);
 
-    createBaseEnv();
-
     corepkgsFS->addFile(
         CanonPath("fetchurl.nix"),
         #include "fetchurl.nix.gen.hh"
     );
+
+    createBaseEnv();
 }
 
 
@@ -1449,11 +1453,13 @@ void ExprSelect::eval(EvalState & state, Env & env, Value & v)
         state.forceValue(*vAttrs, (pos2 ? pos2 : this->pos ) );
 
     } catch (Error & e) {
-        auto pos2r = state.positions[pos2];
-        // FIXME: use MemoryAccessor
-        if (pos2 /* && pos2r.origin != Pos(state.derivationNixPath) */)
-            state.addErrorTrace(e, pos2, "while evaluating the attribute '%1%'",
-                showAttrPath(state, env, attrPath));
+        if (pos2) {
+            auto pos2r = state.positions[pos2];
+            auto origin = std::get_if<SourcePath>(&pos2r.origin);
+            if (!origin || *origin != state.derivationInternal)
+                state.addErrorTrace(e, pos2, "while evaluating the attribute '%1%'",
+                    showAttrPath(state, env, attrPath));
+        }
         throw;
     }
 
diff --git a/src/libexpr/eval.hh b/src/libexpr/eval.hh
index f9814b501..de8fb4e8b 100644
--- a/src/libexpr/eval.hh
+++ b/src/libexpr/eval.hh
@@ -91,8 +91,6 @@ public:
     SymbolTable symbols;
     PosTable positions;
 
-    static inline std::string derivationNixPath = "//builtin/derivation.nix";
-
     const Symbol sWith, sOutPath, sDrvPath, sType, sMeta, sName, sValue,
         sSystem, sOverrides, sOutputs, sOutputName, sIgnoreNulls,
         sFile, sLine, sColumn, sFunctor, sToString,
@@ -103,7 +101,6 @@ public:
         sDescription, sSelf, sEpsilon, sStartSet, sOperator, sKey, sPath,
         sPrefix,
         sOutputSpecified;
-    Symbol sDerivationNix;
 
     /* If set, force copying files to the Nix store even if they
        already exist there. */
@@ -111,8 +108,10 @@ public:
 
     Bindings emptyBindings;
 
-    ref<FSInputAccessor> rootFS;
-    ref<MemoryInputAccessor> corepkgsFS;
+    const ref<FSInputAccessor> rootFS;
+    const ref<MemoryInputAccessor> corepkgsFS;
+
+    const SourcePath derivationInternal;
 
     std::unordered_map<InputAccessor *, ref<InputAccessor>> inputAccessors;
 
diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index 8f8711e8c..5d63c1776 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -3979,8 +3979,6 @@ void EvalState::createBaseEnv()
 
     /* Add a wrapper around the derivation primop that computes the
        `drvPath' and `outPath' attributes lazily. */
-    // FIXME: use corepkgsFS.
-    sDerivationNix = symbols.create(derivationNixPath);
     auto vDerivation = allocValue();
     addConstant("derivation", vDerivation);
 
@@ -3992,12 +3990,7 @@ void EvalState::createBaseEnv()
 
     /* Note: we have to initialize the 'derivation' constant *after*
        building baseEnv/staticBaseEnv because it uses 'builtins'. */
-    char code[] =
-        #include "primops/derivation.nix.gen.hh"
-        // the parser needs two NUL bytes as terminators; one of them
-        // is implied by being a C string.
-        "\0";
-    eval(parse(code, sizeof(code), Pos::string_tag(), rootPath("/"), staticBaseEnv), *vDerivation);
+    evalFile(derivationInternal, *vDerivation);
 }
 
 
diff --git a/src/libfetchers/input-accessor.cc b/src/libfetchers/input-accessor.cc
index a335f1e10..ce1327fda 100644
--- a/src/libfetchers/input-accessor.cc
+++ b/src/libfetchers/input-accessor.cc
@@ -258,9 +258,11 @@ struct MemoryInputAccessorImpl : MemoryInputAccessor
         throw UnimplementedError("MemoryInputAccessor::readLink");
     }
 
-    void addFile(CanonPath path, std::string && contents) override
+    SourcePath addFile(CanonPath path, std::string && contents) override
     {
-        files.emplace(std::move(path), std::move(contents));
+        files.emplace(path, std::move(contents));
+
+        return {ref(shared_from_this()), std::move(path)};
     }
 };
 
diff --git a/src/libfetchers/input-accessor.hh b/src/libfetchers/input-accessor.hh
index 46ae48b2a..3160eaf28 100644
--- a/src/libfetchers/input-accessor.hh
+++ b/src/libfetchers/input-accessor.hh
@@ -77,9 +77,11 @@ ref<FSInputAccessor> makeFSInputAccessor(
     std::optional<std::set<CanonPath>> && allowedPaths = {},
     MakeNotAllowedError && makeNotAllowedError = {});
 
+struct SourcePath;
+
 struct MemoryInputAccessor : InputAccessor
 {
-    virtual void addFile(CanonPath path, std::string && contents) = 0;
+    virtual SourcePath addFile(CanonPath path, std::string && contents) = 0;
 };
 
 ref<MemoryInputAccessor> makeMemoryInputAccessor();