From 6cc2ef7c6d571a668f2e02fa7a485ab8119c8d4b Mon Sep 17 00:00:00 2001
From: eldritch horrors <pennae@lix.systems>
Date: Wed, 14 Jan 2026 17:20:25 +0100
Subject: [PATCH] libexpr: remove RegisterPrimOp static initializer helper

Change-Id: I0cc6d54fca26c66b13f930303086b08b2afb4d54
---
 doc/manual/rl-next/static-initializers.md | 11 +++++++++++
 lix/libexpr/primops.cc                    | 11 ++++++-----
 lix/libexpr/primops.hh                    |  9 +++++++--
 lix/libstore/settings/plugin-files.md     |  2 +-
 tests/functional/plugins/plugintest.cc    | 11 +++++------
 5 files changed, 30 insertions(+), 14 deletions(-)
 create mode 100644 doc/manual/rl-next/static-initializers.md

diff --git a/doc/manual/rl-next/static-initializers.md b/doc/manual/rl-next/static-initializers.md
new file mode 100644
index 000000000..79591d563
--- /dev/null
+++ b/doc/manual/rl-next/static-initializers.md
@@ -0,0 +1,11 @@
+---
+synopsis: "Plugin interfaces have changed (again)"
+cls: [4933]
+issues: [359]
+category: "Miscellany"
+credits: [horrors]
+---
+
+The `RegisterPrimOp` class used to register builtins has been removed. Plugins
+must now call `PluginPrimOps::add` from their `nix_plugin_entry` with the same
+parameters previously passed to `RegisterRrimOp` to register any new builtins.
diff --git a/lix/libexpr/primops.cc b/lix/libexpr/primops.cc
index 51d8106a7..aeafd683e 100644
--- a/lix/libexpr/primops.cc
+++ b/lix/libexpr/primops.cc
@@ -3038,10 +3038,9 @@ static void prim_splitVersion(EvalState & state, Value * * args, Value & v)
  * Primop registration
  *************************************************************/
 
+PluginPrimOps::PrimOps * PluginPrimOps::primOps;
 
-RegisterPrimOp::PrimOps * RegisterPrimOp::primOps;
-
-RegisterPrimOp::RegisterPrimOp(PrimOpDetails && primOp)
+void PluginPrimOps::add(PrimOpDetails && primOp)
 {
     if (!primOps) primOps = new PrimOps;
     primOps->emplace_back(std::move(primOp));
@@ -3083,14 +3082,16 @@ void EvalBuiltins::createBaseEnv(const SearchPath & searchPath, const Path & sto
         });
     }
 
-    if (RegisterPrimOp::primOps)
-        for (auto & primOp : *RegisterPrimOp::primOps)
+    if (PluginPrimOps::primOps) {
+        for (auto & primOp : *PluginPrimOps::primOps) {
             if (experimentalFeatureSettings.isEnabled(primOp.experimentalFeature))
             {
                 auto primOpAdjusted = primOp;
                 primOpAdjusted.arity = std::max(primOp.args.size(), primOp.arity);
                 addPrimOp(std::move(primOpAdjusted));
             }
+        }
+    }
 
     static PrimOp prim_initializeDerivation{{
         .arity = 1,
diff --git a/lix/libexpr/primops.hh b/lix/libexpr/primops.hh
index 556ded156..dcc611f38 100644
--- a/lix/libexpr/primops.hh
+++ b/lix/libexpr/primops.hh
@@ -23,17 +23,22 @@ constexpr size_t nonRecursiveStackReservation = 128;
  */
 constexpr size_t conservativeStackReservation = 16;
 
-struct RegisterPrimOp
+class PluginPrimOps
 {
+    friend EvalBuiltins;
+
     typedef std::vector<PrimOp> PrimOps;
     static PrimOps * primOps;
 
+public:
+    PluginPrimOps() = delete;
+
     /**
      * You can register a constant by passing an arity of 0. fun
      * will get called during EvalState initialization, so there
      * may be primops not yet added and builtins is not yet sorted.
      */
-    RegisterPrimOp(PrimOpDetails && primOp);
+    static void add(PrimOpDetails && primOp);
 };
 
 /* These primops are disabled without enableNativeCode, but plugins
diff --git a/lix/libstore/settings/plugin-files.md b/lix/libstore/settings/plugin-files.md
index 1bc00a0b9..ca8806498 100644
--- a/lix/libstore/settings/plugin-files.md
+++ b/lix/libstore/settings/plugin-files.md
@@ -14,7 +14,7 @@ If an entry in the list is a directory, all files in the directory are loaded as
 FIXME(jade): We should provide a `nix_plugin_finalize()` that gets called at some point in teardown for use cases like nix-otel which need to be able to cleanup, flush things to network, etc, on exit without having to do that from life-after-main().
 
 In particular, these plugins may:
-- Construct static instances of `RegisterPrimOp` to add new primops or constants to the expression language (FIXME: will be replaced with an explicit function).
+- Add new primops or constants to the expression language by calling `PluginPrimOps::add`.
 - Add new store implementations with `StoreImplementations::add`.
 - Construct static instances of `GlobalConfig::Register` to add new config options.
 
diff --git a/tests/functional/plugins/plugintest.cc b/tests/functional/plugins/plugintest.cc
index e91dda774..bcaa8915a 100644
--- a/tests/functional/plugins/plugintest.cc
+++ b/tests/functional/plugins/plugintest.cc
@@ -36,13 +36,12 @@ static void prim_anotherNull (EvalState & state, Value ** args, Value & v)
         v.mkBool(false);
 }
 
-static RegisterPrimOp rp({
-    .name = "anotherNull",
-    .arity = 0,
-    .fun = prim_anotherNull,
-});
-
 extern "C" void nix_plugin_entry()
 {
+    PluginPrimOps::add({
+        .name = "anotherNull",
+        .arity = 0,
+        .fun = prim_anotherNull,
+    });
     entryCalled = true;
 }