refactor(tvix/glue): move nix_path handling to helper in tvix-glue r/6938

Change-Id: I2327560c4cf0d3f90e253e3c2f47cb29c762461e
Reviewed-on: https://cl.tvl.fyi/c/depot/+/9910
Reviewed-by: raitobezarius <tvl@lahfa.xyz>
Autosubmit: flokli <flokli@flokli.de>
Tested-by: BuildkiteCI

3 files changed, 14 insertions, 11 deletions

diff --git a/tvix/cli/src/main.rs b/tvix/cli/src/main.rs
index 1ffa2be256..66705e1307 100644
--- a/tvix/cli/src/main.rs
+++ b/tvix/cli/src/main.rs
@@ -2,8 +2,8 @@ use std::cell::RefCell;
 use std::rc::Rc;
 use std::sync::Arc;
 use std::{fs, path::PathBuf};
-use tvix_glue::add_derivation_builtins;
 use tvix_glue::known_paths::KnownPaths;
+use tvix_glue::{add_derivation_builtins, configure_nix_path};
 
 use clap::Parser;
 use rustyline::{error::ReadlineError, Editor};
@@ -75,6 +75,7 @@ fn interpret(code: &str, path: Option<PathBuf>, args: &Args, explain: bool) -> b
 
     let known_paths: Rc<RefCell<KnownPaths>> = Default::default();
     add_derivation_builtins(&mut eval, known_paths.clone());
+    configure_nix_path(&mut eval, &args.nix_search_path);
 
     let tokio_runtime = tokio::runtime::Runtime::new().unwrap();
     eval.io_handle = Box::new(tvix_glue::tvix_io::TvixIO::new(
@@ -87,14 +88,6 @@ fn interpret(code: &str, path: Option<PathBuf>, args: &Args, explain: bool) -> b
         ),
     ));
 
-    // bundle fetchurl.nix (used in nixpkgs) by resolving <nix> to
-    // `/__corepkgs__`, which has special handling in [`nix_compat`].
-    eval.nix_path = args
-        .nix_search_path
-        .as_ref()
-        .map(|p| format!("nix=/__corepkgs__:{}", p))
-        .or_else(|| Some("nix=/__corepkgs__".to_string()));
-
     let source_map = eval.source_map();
     let result = {
         let mut compiler_observer =
diff --git a/tvix/glue/src/lib.rs b/tvix/glue/src/lib.rs
index acb81d3144..760e730217 100644
--- a/tvix/glue/src/lib.rs
+++ b/tvix/glue/src/lib.rs
@@ -26,3 +26,13 @@ pub fn add_derivation_builtins(
     eval.src_builtins
         .push(("derivation", include_str!("derivation.nix")));
 }
+
+/// Tell the Evaluator to resolve <nix> to the path `/__corepkgs__`,
+/// which has special handling in [tvix_io::TvixIO].
+/// This is used in nixpkgs to import `fetchurl.nix` from `<nix>`.
+pub fn configure_nix_path(eval: &mut tvix_eval::Evaluation, nix_search_path: &Option<String>) {
+    eval.nix_path = nix_search_path
+        .as_ref()
+        .map(|p| format!("nix=/__corepkgs__:{}", p))
+        .or_else(|| Some("nix=/__corepkgs__".to_string()));
+}
diff --git a/tvix/glue/src/tvix_io.rs b/tvix/glue/src/tvix_io.rs
index caadbeb5e6..09e1417a21 100644
--- a/tvix/glue/src/tvix_io.rs
+++ b/tvix/glue/src/tvix_io.rs
@@ -59,8 +59,8 @@ impl<T: EvalIO> EvalIO for TvixIO<T> {
 
     fn read_to_string(&self, path: &Path) -> Result<String, io::Error> {
         // Bundled version of corepkgs/fetchurl.nix. The counterpart
-        // of this happens in `main`, where the `nix_path` of the
-        // evaluation has `nix=/__corepkgs__` added to it.
+        // of this happens in [crate::configure_nix_path], where the `nix_path`
+        // of the evaluation has `nix=/__corepkgs__` added to it.
         //
         // This workaround is similar to what cppnix does for passing
         // the path through.