[M5+] use devbox attr_paths for pinned-dep nixpkgs attr

src/codegen/flake.cpp

@@ -42,14 +42,19 @@ auto sanitize_input_attr(std::string_view name, std::string_view version)
     return std::format("nixpkgs_{}_{}", sanitize(name), sanitize(version));
 }
 
-auto find_lockfile_rev(const lockfile::Lockfile& lock, const std::string& name,
-                       const std::string& version) -> std::optional<std::string> {
+struct LockfileRef {
+    std::optional<std::string> rev;
+    std::optional<std::string> attr;
+};
+
+auto find_lockfile_ref(const lockfile::Lockfile& lock, const std::string& name,
+                       const std::string& version) -> LockfileRef {
     for (const auto& p : lock.packages) {
         if (p.name == name && p.version == version) {
-            return p.nixpkgs_rev;
+            return LockfileRef{.rev = p.nixpkgs_rev, .attr = p.nixpkgs_attr};
         }
     }
-    return std::nullopt;
+    return LockfileRef{};
 }
 
 auto build_bindings(const GenerateInputs& in) -> std::vector<DepBinding> {
@@ -58,12 +63,19 @@ auto build_bindings(const GenerateInputs& in) -> std::vector<DepBinding> {
     for (std::size_t i = 0; i < in.manifest.dependencies.size(); ++i) {
         const auto& dep = in.manifest.dependencies[i];
         const auto& rec = in.recipes[i];
+        auto ref = find_lockfile_ref(in.lock, dep.name, dep.version_spec);
+        // For pinned deps the lockfile's nixpkgs_attr is authoritative
+        // (it came from devbox's attr_paths for this specific rev). The
+        // curated recipe's attr only applies to nixos-unstable, so it's
+        // wrong when the dep pulls from a different rev.
+        std::string attr = (ref.attr && !ref.attr->empty()) ? *ref.attr
+                                                            : rec.nixpkgs_attr;
         DepBinding b{
             .name = dep.name,
             .version = dep.version_spec,
-            .nixpkgs_attr = rec.nixpkgs_attr,
+            .nixpkgs_attr = std::move(attr),
             .sanitized = sanitize_input_attr(dep.name, dep.version_spec),
-            .rev = find_lockfile_rev(in.lock, dep.name, dep.version_spec),
+            .rev = std::move(ref.rev),
         };
         out.push_back(std::move(b));
     }