refactor(tvix/eval): move mocked builtins.derivation to tests r/5619

This placeholder should not live in the main crate anymore as we will
be injecting the real one from outside of eval, but there are still
language tests that depend on a (simple, mockable) version of it.

Change-Id: I68ea169db15cbdbeed320930d3069e21e376c90d
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7783
Reviewed-by: flokli <flokli@flokli.de>
Autosubmit: tazjin <tazjin@tvl.su>
Tested-by: BuildkiteCI

2 files changed, 38 insertions, 36 deletions

diff --git a/tvix/eval/src/builtins/mod.rs b/tvix/eval/src/builtins/mod.rs
index dcc158d10189..7fd66d5afc75 100644
--- a/tvix/eval/src/builtins/mod.rs
+++ b/tvix/eval/src/builtins/mod.rs
@@ -945,7 +945,7 @@ mod pure_builtins {
     }
 }
 
-fn builtin_tuple(builtin: Builtin) -> (&'static str, Value) {
+pub(crate) fn builtin_tuple(builtin: Builtin) -> (&'static str, Value) {
     (builtin.name(), Value::Builtin(builtin))
 }
 
@@ -1036,39 +1036,6 @@ pub fn placeholders() -> Vec<(&'static str, Value)> {
                 Ok(Value::attrs(NixAttrs::from_iter(res.into_iter())))
             },
         ),
-        Builtin::new(
-            "derivation",
-            &[BuiltinArgument {
-                strict: true,
-                name: "attrs",
-            }],
-            None,
-            |args: Vec<Value>, vm: &mut VM| {
-                vm.emit_warning(WarningKind::NotImplemented("builtins.derivation"));
-
-                // We do not implement derivations yet, so this function sets mock
-                // values on the fields that a real derivation would contain.
-                //
-                // Crucially this means we do not yet *validate* the values either.
-                let input = args[0].to_attrs()?;
-                let attrs = input.update(NixAttrs::from_iter(
-                    [
-                        (
-                            "outPath",
-                            "/nix/store/00000000000000000000000000000000-mock",
-                        ),
-                        (
-                            "drvPath",
-                            "/nix/store/00000000000000000000000000000000-mock.drv",
-                        ),
-                        ("type", "derivation"),
-                    ]
-                    .into_iter(),
-                ));
-
-                Ok(Value::Attrs(Box::new(attrs)))
-            },
-        ),
     ];
 
     ph.into_iter().map(builtin_tuple).collect()
diff --git a/tvix/eval/src/tests/mod.rs b/tvix/eval/src/tests/mod.rs
index 9692d50bf11b..9bf9ef353c49 100644
--- a/tvix/eval/src/tests/mod.rs
+++ b/tvix/eval/src/tests/mod.rs
@@ -1,7 +1,37 @@
+use builtin_macros::builtins;
 use pretty_assertions::assert_eq;
-
 use test_generator::test_resources;
 
+#[builtins]
+mod mock_builtins {
+    //! Builtins which are required by language tests, but should not
+    //! actually exist in //tvix/eval.
+    use crate::*;
+
+    #[builtin("derivation")]
+    fn builtin_type_of(vm: &mut VM, input: Value) -> Result<Value, ErrorKind> {
+        vm.emit_warning(WarningKind::NotImplemented("builtins.derivation"));
+
+        let input = input.to_attrs()?;
+        let attrs = input.update(NixAttrs::from_iter(
+            [
+                (
+                    "outPath",
+                    "/nix/store/00000000000000000000000000000000-mock",
+                ),
+                (
+                    "drvPath",
+                    "/nix/store/00000000000000000000000000000000-mock.drv",
+                ),
+                ("type", "derivation"),
+            ]
+            .into_iter(),
+        ));
+
+        Ok(Value::Attrs(Box::new(attrs)))
+    }
+}
+
 fn eval_test(code_path: &str, expect_success: bool) {
     let base = code_path
         .strip_suffix("nix")
@@ -17,7 +47,12 @@ fn eval_test(code_path: &str, expect_success: bool) {
         return;
     }
 
-    let eval = crate::Evaluation::new_impure(&code, Some(code_path.into()));
+    let mut eval = crate::Evaluation::new_impure(&code, Some(code_path.into()));
+    eval.builtins.extend(
+        mock_builtins::builtins()
+            .into_iter()
+            .map(crate::builtins::builtin_tuple),
+    );
 
     let result = eval.evaluate();