refactor(tvix/eval): Builderize Evaluation r/8351

Make constructing of a new Evaluation use the builder pattern rather
than setting public mutable fields. This is currently a pure
refactor (no functionality has changed) but has a few advantages:

- We've encapsulated the internals of the fields in Evaluation, meaning
  we can change them without too much breakage of clients
- We have type safety that prevents us from ever changing the fields of
  an Evaluation after it's built (which matters more in a world where we
  reuse Evaluations).

More importantly, this paves the road for doing different things with
the construction of an Evaluation - notably, sharing certain things like
the GlobalsMap across subsequent evaluations in eg the REPL.

Fixes: b/262
Change-Id: I4a27116faac14cdd144fc7c992d14ae095a1aca4
Reviewed-on: https://cl.tvl.fyi/c/depot/+/11956
Tested-by: BuildkiteCI
Autosubmit: aspen <root@gws.fyi>
Reviewed-by: flokli <flokli@flokli.de>

1 files changed, 23 insertions, 18 deletions

diff --git a/tvix/glue/src/builtins/mod.rs b/tvix/glue/src/builtins/mod.rs
index 3d6263286dc4..e1c20e461ffc 100644
--- a/tvix/glue/src/builtins/mod.rs
+++ b/tvix/glue/src/builtins/mod.rs
@@ -18,13 +18,14 @@ pub use errors::{DerivationError, FetcherError, ImportError};
 ///
 /// As they need to interact with `known_paths`, we also need to pass in
 /// `known_paths`.
-pub fn add_derivation_builtins<IO>(eval: &mut tvix_eval::Evaluation<IO>, io: Rc<TvixStoreIO>) {
-    eval.builtins
-        .extend(derivation::derivation_builtins::builtins(Rc::clone(&io)));
-
-    // Add the actual `builtins.derivation` from compiled Nix code
-    eval.src_builtins
-        .push(("derivation", include_str!("derivation.nix")));
+pub fn add_derivation_builtins<'co, 'ro, 'env, IO>(
+    eval_builder: tvix_eval::EvaluationBuilder<'co, 'ro, 'env, IO>,
+    io: Rc<TvixStoreIO>,
+) -> tvix_eval::EvaluationBuilder<'co, 'ro, 'env, IO> {
+    eval_builder
+        .add_builtins(derivation::derivation_builtins::builtins(Rc::clone(&io)))
+        // Add the actual `builtins.derivation` from compiled Nix code
+        .add_src_builtin("derivation", include_str!("derivation.nix"))
 }
 
 /// Adds fetcher builtins to the passed [tvix_eval::Evaluation]:
@@ -32,9 +33,11 @@ pub fn add_derivation_builtins<IO>(eval: &mut tvix_eval::Evaluation<IO>, io: Rc<
 /// * `fetchurl`
 /// * `fetchTarball`
 /// * `fetchGit`
-pub fn add_fetcher_builtins<IO>(eval: &mut tvix_eval::Evaluation<IO>, io: Rc<TvixStoreIO>) {
-    eval.builtins
-        .extend(fetchers::fetcher_builtins::builtins(Rc::clone(&io)));
+pub fn add_fetcher_builtins<'co, 'ro, 'env, IO>(
+    eval_builder: tvix_eval::EvaluationBuilder<'co, 'ro, 'env, IO>,
+    io: Rc<TvixStoreIO>,
+) -> tvix_eval::EvaluationBuilder<'co, 'ro, 'env, IO> {
+    eval_builder.add_builtins(fetchers::fetcher_builtins::builtins(Rc::clone(&io)))
 }
 
 /// Adds import-related builtins to the passed [tvix_eval::Evaluation].
@@ -42,10 +45,12 @@ pub fn add_fetcher_builtins<IO>(eval: &mut tvix_eval::Evaluation<IO>, io: Rc<Tvi
 /// These are `filterSource` and `path`
 ///
 /// As they need to interact with the store implementation, we pass [`TvixStoreIO`].
-pub fn add_import_builtins<IO>(eval: &mut tvix_eval::Evaluation<IO>, io: Rc<TvixStoreIO>) {
-    eval.builtins.extend(import::import_builtins(io));
-
+pub fn add_import_builtins<'co, 'ro, 'env, IO>(
+    eval_builder: tvix_eval::EvaluationBuilder<'co, 'ro, 'env, IO>,
+    io: Rc<TvixStoreIO>,
+) -> tvix_eval::EvaluationBuilder<'co, 'ro, 'env, IO> {
     // TODO(raitobezarius): evaluate expressing filterSource as Nix code using path (b/372)
+    eval_builder.add_builtins(import::import_builtins(io))
 }
 
 #[cfg(test)]
@@ -81,11 +86,11 @@ mod tests {
             runtime.handle().clone(),
         ));
 
-        let mut eval = tvix_eval::Evaluation::new(io.clone() as Rc<dyn EvalIO>, false);
-
-        add_derivation_builtins(&mut eval, Rc::clone(&io));
-        add_fetcher_builtins(&mut eval, Rc::clone(&io));
-        add_import_builtins(&mut eval, io);
+        let mut eval_builder = tvix_eval::Evaluation::builder(io.clone() as Rc<dyn EvalIO>);
+        eval_builder = add_derivation_builtins(eval_builder, Rc::clone(&io));
+        eval_builder = add_fetcher_builtins(eval_builder, Rc::clone(&io));
+        eval_builder = add_import_builtins(eval_builder, io);
+        let eval = eval_builder.build();
 
         // run the evaluation itself.
         eval.evaluate(str, None)