test(tvix): Fix tvix tests on macOS

Prior to this, some tests would not build
or would fail in an obscure way.

Change-Id: I68587cc7592492ebfd71ca02fc7ccc9ff7c0196f
Reviewed-on: https://cl.tvl.fyi/c/depot/+/11544
Tested-by: BuildkiteCI
Reviewed-by: flokli <flokli@flokli.de>

tvix/castore/src/fs/inodes.rs

@@ -57,16 +57,18 @@ impl InodeData {
                     children.len() as u64
                 }
             },
-            mode: match self {
-                InodeData::Regular(_, _, false) => libc::S_IFREG | 0o444, // no-executable files
-                InodeData::Regular(_, _, true) => libc::S_IFREG | 0o555,  // executable files
-                InodeData::Symlink(_) => libc::S_IFLNK | 0o444,
-                InodeData::Directory(_) => libc::S_IFDIR | 0o555,
-            },
+            mode: self.as_fuse_type() | self.mode(),
             ..Default::default()
         }
     }
 
+    fn mode(&self) -> u32 {
+        match self {
+            InodeData::Regular(_, _, false) | InodeData::Symlink(_) => 0o444,
+            InodeData::Regular(_, _, true) | InodeData::Directory(_) => 0o555,
+        }
+    }
+
     pub fn as_fuse_entry(&self, inode: u64) -> fuse_backend_rs::api::filesystem::Entry {
         fuse_backend_rs::api::filesystem::Entry {
             inode,

tvix/eval/tests/nix_oracle.rs

@@ -30,7 +30,14 @@ fn nix_eval(expr: &str, strictness: Strictness) -> String {
         .arg(format!("({expr})"))
         .env(
             "NIX_REMOTE",
-            format!("local?root={}", store_dir.path().display()),
+            format!(
+                "local?root={}",
+                store_dir
+                    .path()
+                    .canonicalize()
+                    .expect("valid path")
+                    .display()
+            ),
         )
         .output()
         .unwrap();

tvix/glue/src/builtins/mod.rs

@@ -739,6 +739,7 @@ mod tests {
         false
     )]
     fn builtins_filter_source_unsupported_files(#[case] code: &str, #[case] exp_success: bool) {
+        use nix::errno::Errno;
         use nix::sys::stat;
         use nix::unistd;
         use std::os::unix::net::UnixListener;
@@ -765,6 +766,15 @@ mod tests {
             stat::Mode::S_IRWXU,
             0,
         )
+        .inspect_err(|e| {
+            if *e == Errno::EPERM {
+                eprintln!(
+                    "\
+Missing permissions to create a character device node with mknod(2).
+Please run this test as root or set CAP_MKNOD."
+                );
+            }
+        })
         .expect("Failed to create a character device node");
 
         let code_replaced = code.replace("@fixtures", &temp.path().to_string_lossy());