Eastwooder · January 6, 2025 21:49 · Jan 6, 2025
diff --git a/Cargo.toml b/Cargo.toml
@@ -0,0 +1,9 @@
+[package]
+name = "starlark-playground"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+allocative = "0.3.4"
+indoc = "2.0.5"
+starlark = "0.13.0"
diff --git a/main.rs b/main.rs
@@ -0,0 +1,89 @@
+use allocative::Allocative;
+use indoc::indoc;
+use starlark::any::ProvidesStaticType;
+use starlark::environment::{GlobalsBuilder, Module};
+use starlark::eval::Evaluator;
+use starlark::syntax::{AstModule, Dialect};
+use starlark::values::none::NoneType;
+use starlark::values::{starlark_value, Heap, NoSerialize, StarlarkValue, Value};
+use starlark::{starlark_module, starlark_simple_value};
+use std::cell::RefCell;
+use std::fmt::{Display, Formatter};
+
+fn main() -> starlark::Result<()> {
+    let content = indoc! {"
+        def my_loop(members):
+            for item in members:
+                emit(item)
+
+        emit(fetch().name)
+        my_loop(fetch().members)
+    "};
+    let ast = AstModule::parse("complex.star", content.to_owned(), &Dialect::Standard)?;
+    let globals = GlobalsBuilder::new().with(starlark_fetch).build();
+    let module = Module::new();
+    let store = Store::default();
+    {
+        let mut eval = Evaluator::new(&module);
+        eval.extra = Some(&store);
+        let _ = eval.eval_module(ast, &globals)?;
+    }
+    for emitted in &*store.0.borrow() {
+        println!("emitted: {emitted}");
+    }
+    Ok(())
+}
+
+// Define a store in which to accumulate JSON strings
+#[derive(Debug, ProvidesStaticType, Default)]
+struct Store(RefCell<Vec<String>>);
+
+impl Store {
+    fn add(&self, x: String) {
+        self.0.borrow_mut().push(x)
+    }
+}
+
+#[starlark_module]
+fn starlark_fetch(builder: &mut GlobalsBuilder) {
+    fn fetch(eval: &mut Evaluator) -> starlark::Result<Extr> {
+        Ok(Extr {
+            name: "test".to_string(),
+            members: vec!["a".to_string(), "b".to_string()],
+        })
+    }
+    fn emit(x: Value, eval: &mut Evaluator) -> starlark::Result<NoneType> {
+        // We modify extra (which we know is a Store) and add the JSON of the
+        // value the user gave.
+        eval.extra
+            .unwrap()
+            .downcast_ref::<Store>()
+            .unwrap()
+            .add(x.to_json()?);
+        Ok(NoneType)
+    }
+}
+
+#[derive(Debug, Clone, ProvidesStaticType, NoSerialize, Allocative)]
+pub struct Extr {
+    pub name: String,
+    pub members: Vec<String>,
+}
+starlark_simple_value!(Extr);
+
+impl Display for Extr {
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+        write!(f, "Extr[name={name}]", name = self.name)
+    }
+}
+
+#[starlark_value(type = "Extr")]
+impl<'v> StarlarkValue<'v> for Extr {
+    fn get_attr(&self, attribute: &str, heap: &'v Heap) -> Option<Value<'v>> {
+        match attribute {
+            "name" => Some(heap.alloc(self.name.clone())),
+            "members" => Some(heap.alloc(self.members.clone())),
+            _ => None,
+        }
+    }
+}