From 7308fde0bc0ee9a902891385453ef6313cb91194 Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <edolstra@gmail.com>
Date: Thu, 23 Oct 2025 19:18:57 +0200
Subject: [PATCH] Allow access to the result of fetchClosure

---
 src/libexpr/primops/fetchClosure.cc       | 6 ++++++
 tests/functional/dependencies.builder0.sh | 2 ++
 tests/functional/fetchClosure.sh          | 8 ++++++++
 3 files changed, 16 insertions(+)

diff --git a/src/libexpr/primops/fetchClosure.cc b/src/libexpr/primops/fetchClosure.cc
index 63da53aa9..6e1389814 100644
--- a/src/libexpr/primops/fetchClosure.cc
+++ b/src/libexpr/primops/fetchClosure.cc
@@ -64,6 +64,8 @@ static void runFetchClosureWithRewrite(
              .pos = state.positions[pos]});
     }
 
+    state.allowClosure(toPath);
+
     state.mkStorePathString(toPath, v);
 }
 
@@ -91,6 +93,8 @@ static void runFetchClosureWithContentAddressedPath(
              .pos = state.positions[pos]});
     }
 
+    state.allowClosure(fromPath);
+
     state.mkStorePathString(fromPath, v);
 }
 
@@ -115,6 +119,8 @@ static void runFetchClosureWithInputAddressedPath(
              .pos = state.positions[pos]});
     }
 
+    state.allowClosure(fromPath);
+
     state.mkStorePathString(fromPath, v);
 }
 
diff --git a/tests/functional/dependencies.builder0.sh b/tests/functional/dependencies.builder0.sh
index 6fbe4a07a..f680cf7f2 100644
--- a/tests/functional/dependencies.builder0.sh
+++ b/tests/functional/dependencies.builder0.sh
@@ -17,4 +17,6 @@ ln -s "$out" "$out"/self
 echo program > "$out"/program
 chmod +x "$out"/program
 
+echo '1 + 2' > "$out"/foo.nix
+
 echo FOO
diff --git a/tests/functional/fetchClosure.sh b/tests/functional/fetchClosure.sh
index 9b79ab396..85a83d192 100755
--- a/tests/functional/fetchClosure.sh
+++ b/tests/functional/fetchClosure.sh
@@ -99,6 +99,14 @@ clearStore
 
 [ -e "$caPath" ]
 
+# Test import-from-derivation on the result of fetchClosure.
+[[ $(nix eval -v --expr "
+  import \"\${builtins.fetchClosure {
+    fromStore = \"file://$cacheDir\";
+    fromPath = $caPath;
+  }}/foo.nix\"
+") = 3 ]]
+
 # Check that URL query parameters aren't allowed.
 clearStore
 narCache=$TEST_ROOT/nar-cache