fix(tvix/eval): don't thunk home relative paths r/6297

C++ Nix resolves home relative paths at [parse] time. This is not an
option for us, since it prevents being able to separate the compilation
and execution phase later (e.g. precompiled nix expressions). However, a
practical consequence of this is that paths expressions are always
literals (strict) and never thunks.

[parse]: https://github.com/NixOS/nix/blob/7066d21a0ddb421967980094222c4bc1f5a0f45a/src/libexpr/parser.y#L518-L527

Change-Id: Ie4b9dc68f62c86d6c7fd5f1c9460c850d97ed1ca
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7041
Tested-by: BuildkiteCI
Reviewed-by: tazjin <tazjin@tvl.su>

2 files changed, 13 insertions, 11 deletions

diff --git a/tvix/eval/src/compiler/mod.rs b/tvix/eval/src/compiler/mod.rs
index 43dab506c5ed..436e504af2a6 100644
--- a/tvix/eval/src/compiler/mod.rs
+++ b/tvix/eval/src/compiler/mod.rs
@@ -341,18 +341,17 @@ impl Compiler<'_> {
         let path = if raw_path.starts_with('/') {
             Path::new(&raw_path).to_owned()
         } else if raw_path.starts_with('~') {
-            return self.thunk(slot, node, move |c, _| {
-                // We assume that home paths start with ~/ or fail to parse
-                // TODO: this should be checked using a parse-fail test.
-                debug_assert!(raw_path.len() > 2 && raw_path.starts_with("~/"));
+            // We assume that home paths start with ~/ or fail to parse
+            // TODO: this should be checked using a parse-fail test.
+            debug_assert!(raw_path.len() > 2 && raw_path.starts_with("~/"));
 
-                let home_relative_path = &raw_path[2..(raw_path.len())];
-                c.emit_constant(
-                    Value::UnresolvedPath(Box::new(home_relative_path.into())),
-                    node,
-                );
-                c.push_op(OpCode::OpResolveHomePath, node);
-            });
+            let home_relative_path = &raw_path[2..(raw_path.len())];
+            self.emit_constant(
+                Value::UnresolvedPath(Box::new(home_relative_path.into())),
+                node,
+            );
+            self.push_op(OpCode::OpResolveHomePath, node);
+            return;
         } else if raw_path.starts_with('<') {
             // TODO: decide what to do with findFile
             if raw_path.len() == 2 {
diff --git a/tvix/eval/tests/nix_oracle.rs b/tvix/eval/tests/nix_oracle.rs
index 386d49c51ccd..b9531c81ddc0 100644
--- a/tvix/eval/tests/nix_oracle.rs
+++ b/tvix/eval/tests/nix_oracle.rs
@@ -154,6 +154,9 @@ compare_lazy_eval_tests! {
     thunked_lambda_in_list("[ (x: x) ]");
     thunked_function_application_in_list("[ (builtins.add 1 2) ]");
     thunked_legacy_let_in_list("[ (let { foo = 12; body = foo; }) ]");
+    unthunked_relative_path("[ ./foo ]");
+    unthunked_home_relative_path("[ ~/foo ]");
+    unthunked_absolute_path("[ /foo ]");
 
     unthunked_formals_fallback_literal("({ foo ? 12 }: [ foo ]) { }");
     unthunked_formals_fallback_string_literal("({ foo ? \"wiggly\" }: [ foo ]) { }");