From c1f75860d6ed402a17ca9c57b770ed952a42e3bb Mon Sep 17 00:00:00 2001
From: piegames <git@piegames.de>
Date: Wed, 15 Apr 2026 17:46:45 +0200
Subject: [PATCH] builtins.flakeRefToString: Force the arguments

Without this, the primop chokes on any thunks on attributes passed in
the attrset. It even is the reason why the test contained `builtins.seq`
to work around this. Supposedly, this might have been an intentional
restriction and changing this might break things in ways I cannot forsee
due to not knowing much about Flakes, however the status quo is equally
broken:

- The error message looks like an internal error and not like some
explicitly forbidden invariant violation.
- Seemingly simple syntax literals like "-1" compile to "__sub 0 1" and
thus create a thunk which then fails, which is utterly confusing ("why
does 1 work but not -1?")
- This is a stark violation of the principle of least surprise.
- Thunking relies on maybeThunk and thunk inlining optimizations, thus
not forcing thunks turns operational details of the evaluator into
language-observable behavior. That's bad.

I am changing this now regardless of the risk of breakage, because the
bytecode evaluator will have different thunk inlining optimizations and
thus inevitably cause mismatches in behavior anyways.

Change-Id: Ifc45c4d2900e40822383670b28e4e50ab8af317a
---
 lix/libexpr/flake/flake.cc                        |  1 +
 .../eval-fail-negative-integer.err.exp            | 15 +++++----------
 .../in-negative-integer.nix                       |  7 +++++--
 3 files changed, 11 insertions(+), 12 deletions(-)

diff --git a/lix/libexpr/flake/flake.cc b/lix/libexpr/flake/flake.cc
index 94ba34433..9e3711a48 100644
--- a/lix/libexpr/flake/flake.cc
+++ b/lix/libexpr/flake/flake.cc
@@ -1015,6 +1015,7 @@ Value prim_flakeRefToString(EvalState & state, Value ** args)
         "while evaluating the argument passed to builtins.flakeRefToString");
     fetchers::Attrs attrs;
     for (const auto & attr : *args[0]->attrs()) {
+        state.forceValue(attr.value, noPos);
         auto t = attr.value.type();
         if (t == nInt) {
             auto intValue = attr.value.integer().value;
diff --git a/tests/functional2/lang/builtins.flakeRefToString/eval-fail-negative-integer.err.exp b/tests/functional2/lang/builtins.flakeRefToString/eval-fail-negative-integer.err.exp
index fdb4a591a..5e8db03ae 100644
--- a/tests/functional2/lang/builtins.flakeRefToString/eval-fail-negative-integer.err.exp
+++ b/tests/functional2/lang/builtins.flakeRefToString/eval-fail-negative-integer.err.exp
@@ -1,14 +1,9 @@
 error:
-       … while calling the 'seq' builtin
-         at /pwd/in.nix:1:16:
-            1| let n = -1; in builtins.seq n (builtins.flakeRefToString {
-             |                ^
-            2|   type  = "github";
-
        … while calling the 'flakeRefToString' builtin
-         at /pwd/in.nix:1:32:
-            1| let n = -1; in builtins.seq n (builtins.flakeRefToString {
-             |                                ^
-            2|   type  = "github";
+         at /pwd/in.nix:4:1:
+            3| in
+            4| builtins.flakeRefToString {
+             | ^
+            5|   type  = "github";
 
        error: negative value given for flake ref attr repo: -1
diff --git a/tests/functional2/lang/builtins.flakeRefToString/in-negative-integer.nix b/tests/functional2/lang/builtins.flakeRefToString/in-negative-integer.nix
index e0208eb25..790f138ca 100644
--- a/tests/functional2/lang/builtins.flakeRefToString/in-negative-integer.nix
+++ b/tests/functional2/lang/builtins.flakeRefToString/in-negative-integer.nix
@@ -1,7 +1,10 @@
-let n = -1; in builtins.seq n (builtins.flakeRefToString {
+let
+  n = -1;
+in
+builtins.flakeRefToString {
   type  = "github";
   owner = "NixOS";
   repo  = n;
   ref   = "23.05";
   dir   = "lib";
-})
+}