feat: piping syntax

google/jsonnet#612
Signed-off-by: Yaroslav Bolyukin <iam@lach.pw>

crates/jrsonnet-evaluator/src/evaluate/mod.rs

@@ -643,6 +643,22 @@ pub fn evaluate(ctx: Context, expr: &LocExpr) -> Result<Val> {
 
 			IndexableVal::into_untyped(indexable.into_indexable()?.slice(start, end, step)?)?
 		}
+		Pipe(value, mappers) => {
+			let mut value = evaluate(ctx.clone(), value)?;
+			for mapper in mappers {
+				let mapper_ctx = ctx.clone().with_var("_".into(), value.clone());
+				let mapper = evaluate(mapper_ctx, mapper)?;
+				value = match mapper {
+					Val::Null => value,
+					Val::Func(f) => {
+						let native = f.into_native::<((Val,), Val)>();
+						native(value)?
+					}
+					_ => mapper,
+				};
+			}
+			value
+		}
 		i @ (Import(path) | ImportStr(path) | ImportBin(path)) => {
 			let Expr::Str(path) = &*path.0 else {
 				throw!("computed imports are not supported")

crates/jrsonnet-parser/src/expr.rs

@@ -410,6 +410,8 @@ pub enum Expr {
 		cond_else: Option<LocExpr>,
 	},
 	Slice(LocExpr, SliceDesc),
+	/// |> expr1 |> expr2
+	Pipe(LocExpr, Vec<LocExpr>),
 }
 
 /// file, begin offset, end offset

crates/jrsonnet-parser/src/lib.rs

@@ -288,13 +288,14 @@ parser! {
 		rule unaryop(x: rule<()>) -> ()
 			= quiet!{ x() } / expected!("<unary op>")
 
-
 		use BinaryOpType::*;
 		use UnaryOpType::*;
 		rule expr(s: &ParserSettings) -> LocExpr
 			= precedence! {
 				start:position!() v:@ end:position!() { LocExpr(Rc::new(v), ExprLocation(s.source.clone(), start as u32, end as u32)) }
 				--
+				a:@ e:(_ "|>" _ e:expr(s) {e})+ {Expr::Pipe(a, e)}
+				--
 				a:(@) _ binop(<"||">) _ b:@ {expr_bin!(a Or b)}
 				--
 				a:(@) _ binop(<"&&">) _ b:@ {expr_bin!(a And b)}