From c7fb88801c20f00b5114f38231a5b76df0429e7c Mon Sep 17 00:00:00 2001
From: Yaroslav Bolyukin <iam@lach.pw>
Date: Sun, 17 Apr 2022 18:42:07 +0000
Subject: [PATCH] feat: FuncDesc helper for default context


---
--- a/crates/jrsonnet-evaluator/src/function.rs
+++ b/crates/jrsonnet-evaluator/src/function.rs
@@ -23,6 +23,18 @@
 	}
 }
 
+#[derive(Trace)]
+struct EvaluateNamedLazyVal {
+	future_context: FutureWrapper<Context>,
+	name: IStr,
+	value: LocExpr,
+}
+impl LazyValValue for EvaluateNamedLazyVal {
+	fn get(self: Box<Self>) -> Result<Val> {
+		evaluate_named(self.future_context.unwrap(), &self.value, self.name)
+	}
+}
+
 pub trait ArgLike {
 	fn evaluate_arg(&self, ctx: Context, tailstrict: bool) -> Result<LazyVal>;
 }
@@ -309,25 +321,14 @@
 	if filled_args < params.len() {
 		// Some args are unset, but maybe we have defaults for them
 		// Default values should be created in newly created context
-		let future_context = FutureWrapper::<Context>::new();
+		let future_context = Context::new_future();
 		let mut defaults = GcHashMap::with_capacity(params.len() - filled_args);
 
 		for param in params.iter().filter(|p| p.1.is_some()) {
 			if passed_args.contains_key(&param.0.clone()) {
 				continue;
 			}
-			#[derive(Trace)]
-			struct LazyNamedBinding {
-				future_context: FutureWrapper<Context>,
-				name: IStr,
-				value: LocExpr,
-			}
-			impl LazyValValue for LazyNamedBinding {
-				fn get(self: Box<Self>) -> Result<Val> {
-					evaluate_named(self.future_context.unwrap(), &self.value, self.name)
-				}
-			}
-			LazyVal::new(TraceBox(Box::new(LazyNamedBinding {
+			LazyVal::new(TraceBox(Box::new(EvaluateNamedLazyVal {
 				future_context: future_context.clone(),
 				name: param.0.clone(),
 				value: param.1.clone().unwrap(),
@@ -335,7 +336,7 @@
 
 			defaults.insert(
 				param.0.clone(),
-				LazyVal::new(TraceBox(Box::new(LazyNamedBinding {
+				LazyVal::new(TraceBox(Box::new(EvaluateNamedLazyVal {
 					future_context: future_context.clone(),
 					name: param.0.clone(),
 					value: param.1.clone().unwrap(),
@@ -464,3 +465,39 @@
 	}
 	Ok(passed_args)
 }
+
+/// Creates Context, which has all argument default values applied
+/// and with unbound values causing error to be returned
+pub fn parse_default_function_call(body_ctx: Context, params: &ParamsDesc) -> Context {
+	let ctx = Context::new_future();
+
+	let mut bindings = GcHashMap::new();
+
+	#[derive(Trace)]
+	struct DependsOnUnbound(IStr);
+	impl LazyValValue for DependsOnUnbound {
+		fn get(self: Box<Self>) -> Result<Val> {
+			Err(FunctionParameterNotBoundInCall(self.0.clone()).into())
+		}
+	}
+
+	for param in params.iter() {
+		if let Some(v) = &param.1 {
+			bindings.insert(
+				param.0.clone(),
+				LazyVal::new(TraceBox(Box::new(EvaluateNamedLazyVal {
+					future_context: ctx.clone(),
+					name: param.0.clone(),
+					value: v.clone(),
+				}))),
+			);
+		} else {
+			bindings.insert(
+				param.0.clone(),
+				LazyVal::new(TraceBox(Box::new(DependsOnUnbound(param.0.clone())))),
+			);
+		}
+	}
+
+	body_ctx.extend(bindings, None, None, None).into_future(ctx)
+}
--- a/crates/jrsonnet-evaluator/src/val.rs
+++ b/crates/jrsonnet-evaluator/src/val.rs
@@ -5,7 +5,9 @@
 	cc_ptr_eq,
 	error::{Error::*, LocError},
 	evaluate,
-	function::{parse_function_call, ArgsLike, Builtin, StaticBuiltin},
+	function::{
+		parse_default_function_call, parse_function_call, ArgsLike, Builtin, StaticBuiltin,
+	},
 	gc::TraceBox,
 	throw, Context, ObjValue, Result,
 };
@@ -84,6 +86,22 @@
 	pub params: ParamsDesc,
 	pub body: LocExpr,
 }
+impl FuncDesc {
+	/// Create body context, but fill arguments without defaults with lazy error
+	pub fn default_body_context(&self) -> Context {
+		parse_default_function_call(self.ctx.clone(), &self.params)
+	}
+
+	/// Create context, with which body code will run
+	pub fn call_body_context(
+		&self,
+		call_ctx: Context,
+		args: &dyn ArgsLike,
+		tailstrict: bool,
+	) -> Result<Context> {
+		parse_function_call(call_ctx, self.ctx.clone(), &self.params, args, tailstrict)
+	}
+}
 
 #[derive(Trace, Clone)]
 pub enum FuncVal {
@@ -140,16 +158,10 @@
 	) -> Result<Val> {
 		match self {
 			Self::Normal(func) => {
-				let ctx = parse_function_call(
-					call_ctx,
-					func.ctx.clone(),
-					&func.params,
-					args,
-					tailstrict,
-				)?;
-				evaluate(ctx, &func.body)
+				let body_ctx = func.call_body_context(call_ctx, args, tailstrict)?;
+				evaluate(body_ctx, &func.body)
 			}
-			Self::StaticBuiltin(name) => name.call(call_ctx, loc, args),
+			Self::StaticBuiltin(b) => b.call(call_ctx, loc, args),
 			Self::Builtin(b) => b.call(call_ctx, loc, args),
 		}
 	}

-- 
gitstuff