feat(tvix/eval): Add docstrings as documentation for builtins r/5269

Add a new `documentation: Option<&'static str>` field to Builtin, and
populate it in the `#[builtins]` macro with the docstring of the builtin
function, if any.

Change-Id: Ic68fdf9b314d15a780731974234e2ae43f6a44b0
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7205
Tested-by: BuildkiteCI
Reviewed-by: tazjin <tazjin@tvl.su>

1 files changed, 4 insertions, 0 deletions

diff --git a/tvix/eval/builtin-macros/tests/tests.rs b/tvix/eval/builtin-macros/tests/tests.rs
index d07020f69bb7..b270594b0f33 100644
--- a/tvix/eval/builtin-macros/tests/tests.rs
+++ b/tvix/eval/builtin-macros/tests/tests.rs
@@ -7,6 +7,7 @@ mod builtins {
     use tvix_eval::internal::VM;
     use tvix_eval::{ErrorKind, Value};
 
+    /// Test docstring
     #[builtin("identity")]
     pub fn builtin_identity(_vm: &mut VM, x: Value) -> Result<Value, ErrorKind> {
         Ok(x)
@@ -22,4 +23,7 @@ mod builtins {
 fn builtins() {
     let builtins = builtins::builtins();
     assert_eq!(builtins.len(), 2);
+
+    let identity = builtins.iter().find(|b| b.name() == "identity").unwrap();
+    assert_eq!(identity.documentation(), Some(" Test docstring"));
 }