1 files changed, 36 insertions, 0 deletions
diff --git a/tvix/glue/src/builtins/utils.rs b/tvix/glue/src/builtins/utils.rs
new file mode 100644
index 0000000000..586169beeb
--- /dev/null
+++ b/tvix/glue/src/builtins/utils.rs
@@ -0,0 +1,36 @@
+use bstr::ByteSlice;
+use tvix_eval::{
+    generators::{self, GenCo},
+    CatchableErrorKind, CoercionKind, ErrorKind, NixAttrs, NixString, Value,
+};
+
+pub(super) async fn strong_importing_coerce_to_string(
+    co: &GenCo,
+    val: Value,
+) -> Result<NixString, CatchableErrorKind> {
+    let val = generators::request_force(co, val).await;
+    generators::request_string_coerce(
+        co,
+        val,
+        CoercionKind {
+            strong: true,
+            import_paths: true,
+        },
+    )
+    .await
+}
+
+pub(super) async fn select_string(
+    co: &GenCo,
+    attrs: &NixAttrs,
+    key: &str,
+) -> Result<Result<Option<String>, CatchableErrorKind>, ErrorKind> {
+    if let Some(attr) = attrs.select(key) {
+        match strong_importing_coerce_to_string(co, attr.clone()).await {
+            Err(cek) => return Ok(Err(cek)),
+            Ok(str) => return Ok(Ok(Some(str.to_str()?.to_owned()))),
+        }
+    }
+
+    Ok(Ok(None))
+}