3 files changed, 16 insertions, 0 deletions
diff --git a/tvix/eval/src/builtins/mod.rs b/tvix/eval/src/builtins/mod.rs
index a5ca2114e1f7..f6af16f96f9d 100644
--- a/tvix/eval/src/builtins/mod.rs
+++ b/tvix/eval/src/builtins/mod.rs
@@ -134,6 +134,12 @@ fn pure_builtins() -> Vec<Builtin> {
         Builtin::new("length", &[true], |args, _| {
             Ok(Value::Integer(args[0].to_list()?.len() as i64))
         }),
+        Builtin::new("hasAttr", &[true, true], |args, _| {
+            let k = args[0].to_str()?;
+            let xs = args[1].to_attrs()?;
+
+            Ok(Value::Bool(xs.contains(k.as_str())))
+        }),
         Builtin::new("head", &[true], |args, _| match args[0].to_list()?.get(0) {
             Some(x) => Ok(x.clone()),
             None => Err(ErrorKind::IndexOutOfBounds { index: 0 }),
diff --git a/tvix/eval/src/tests/tvix_tests/eval-okay-builtins-hasattr.exp b/tvix/eval/src/tests/tvix_tests/eval-okay-builtins-hasattr.exp
new file mode 100644
index 000000000000..541fe347cbcd
--- /dev/null
+++ b/tvix/eval/src/tests/tvix_tests/eval-okay-builtins-hasattr.exp
@@ -0,0 +1 @@
+[ true true true false false true false ]
diff --git a/tvix/eval/src/tests/tvix_tests/eval-okay-builtins-hasattr.nix b/tvix/eval/src/tests/tvix_tests/eval-okay-builtins-hasattr.nix
new file mode 100644
index 000000000000..e87e186b641d
--- /dev/null
+++ b/tvix/eval/src/tests/tvix_tests/eval-okay-builtins-hasattr.nix
@@ -0,0 +1,9 @@
+[
+  (builtins.hasAttr "foo" { foo = 1; bar = 2; baz = 3; })
+  (builtins.hasAttr "bar" { foo = 1; bar = 2; baz = 3; })
+  (builtins.hasAttr "baz" { foo = 1; bar = 2; baz = 3; })
+  (builtins.hasAttr "FOO" { foo = 1; bar = 2; baz = 3; })
+  (builtins.hasAttr "foo" {})
+  (builtins.hasAttr ("f" + "o" + "o") { foo = 1; })
+  (builtins.hasAttr ("b" + "a" + "r") { foo = 1; })
+]