feat(tvix/tests): Import default.nix inside directory r/5068

This requires actually passing the source directory into `interpret` in
the eval tests, but otherwise this is fairly straightforward - if we're
trying to import a directory, just push `default.nix` onto it and import
that instead.

Change-Id: I0b7d4234f81977e78d14dfa651bf0cf9721017e5
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6893
Autosubmit: grfn <grfn@gws.fyi>
Reviewed-by: sterni <sternenseemann@systemli.org>
Tested-by: BuildkiteCI

1 files changed, 4 insertions, 1 deletions

diff --git a/tvix/eval/src/builtins/impure.rs b/tvix/eval/src/builtins/impure.rs
index a1bcc602dc89..8e23003edb47 100644
--- a/tvix/eval/src/builtins/impure.rs
+++ b/tvix/eval/src/builtins/impure.rs
@@ -52,7 +52,10 @@ pub fn builtins_import(
         "import",
         &[true],
         move |mut args: Vec<Value>, vm: &mut VM| {
-            let path = super::coerce_value_to_path(&args.pop().unwrap(), vm)?;
+            let mut path = super::coerce_value_to_path(&args.pop().unwrap(), vm)?;
+            if path.is_dir() {
+                path.push("default.nix");
+            }
 
             let contents =
                 std::fs::read_to_string(&path).map_err(|err| ErrorKind::ReadFileError {