From 818fc68db687ce3bc769760629967eb340ed931d Mon Sep 17 00:00:00 2001
From: Robert Hensing <robert@roberthensing.nl>
Date: Tue, 15 Apr 2025 09:28:23 +0200
Subject: [PATCH] fix: Evaluate flake parent source without evaluating its
 outputs

This requires that we refer to the `sourceInfo` instead of the
`result`. However, `sourceInfo` does not create a chain of basedir
resolution, so we add that back with `flakeDir`.

(cherry picked from commit 2109a5a2066d0d49a1bcc5b44b2a4d84b5d313bd)
---
 src/libflake/call-flake.nix               | 11 ++++++++++-
 tests/functional/flakes/relative-paths.sh | 21 +++++++++++++++++++++
 2 files changed, 31 insertions(+), 1 deletion(-)

diff --git a/src/libflake/call-flake.nix b/src/libflake/call-flake.nix
index 430dfabdd..fe326291f 100644
--- a/src/libflake/call-flake.nix
+++ b/src/libflake/call-flake.nix
@@ -42,13 +42,20 @@ let
 
       parentNode = allNodes.${getInputByPath lockFile.root node.parent};
 
+      flakeDir =
+        let
+          dir = overrides.${key}.dir or node.locked.path or "";
+          parentDir = parentNode.flakeDir;
+        in
+        if node ? parent then parentDir + ("/" + dir) else dir;
+
       sourceInfo =
         if overrides ? ${key} then
           overrides.${key}.sourceInfo
         else if node.locked.type == "path" && builtins.substring 0 1 node.locked.path != "/" then
           parentNode.sourceInfo
           // {
-            outPath = parentNode.result.outPath + ("/" + node.locked.path);
+            outPath = parentNode.sourceInfo.outPath + ("/" + flakeDir);
           }
         else
           # FIXME: remove obsolete node.info.
@@ -93,6 +100,8 @@ let
           result
         else
           sourceInfo;
+
+      inherit flakeDir sourceInfo;
     }
   ) lockFile.nodes;
 
diff --git a/tests/functional/flakes/relative-paths.sh b/tests/functional/flakes/relative-paths.sh
index 3f7ca3f46..4648ba98c 100644
--- a/tests/functional/flakes/relative-paths.sh
+++ b/tests/functional/flakes/relative-paths.sh
@@ -108,3 +108,24 @@ EOF
 [[ $(nix eval "$rootFlake#z") = 90 ]]
 
 fi
+
+# https://github.com/NixOS/nix/pull/10089#discussion_r2041984987
+# https://github.com/NixOS/nix/issues/13018
+mkdir -p "$TEST_ROOT/issue-13018/example"
+(
+  cd "$TEST_ROOT/issue-13018"
+  git init
+  echo '{ outputs = _: { }; }' >flake.nix
+  cat >example/flake.nix <<EOF
+{
+  inputs.parent.url = ../.;
+  outputs = { parent, ... }: builtins.seq parent { ok = null; };
+}
+EOF
+  git add -N .
+  cd example
+  # Important: the error does not trigger for an in-memory lock!
+  nix flake lock
+  # would fail:
+  nix eval .#ok
+)