From 098d931f0d92480fbe938f936cf3e6731516d3d5 Mon Sep 17 00:00:00 2001
From: Yaroslav Bolyukin <iam@lach.pw>
Date: Thu, 15 Aug 2024 17:45:07 +0200
Subject: [PATCH] fix: #[derive(Typed)] should lazily process Thunks

Fixes: https://github.com/CertainLach/jrsonnet/issues/172
---
 crates/jrsonnet-evaluator/src/obj.rs |  4 ++--
 crates/jrsonnet-macros/src/lib.rs    | 32 +++++++++++++++++++++-------
 2 files changed, 26 insertions(+), 10 deletions(-)

diff --git a/crates/jrsonnet-evaluator/src/obj.rs b/crates/jrsonnet-evaluator/src/obj.rs
index e00b8d2..106359e 100644
--- a/crates/jrsonnet-evaluator/src/obj.rs
+++ b/crates/jrsonnet-evaluator/src/obj.rs
@@ -957,9 +957,9 @@ impl ObjMemberBuilder<ValueBuilder<'_>> {
 
 	/// Tries to insert value, returns an error if it was already defined
 	pub fn try_value(self, value: impl Into<Val>) -> Result<()> {
-		self.thunk(Thunk::evaluated(value.into()))
+		self.try_thunk(Thunk::evaluated(value.into()))
 	}
-	pub fn thunk(self, value: impl Into<Thunk<Val>>) -> Result<()> {
+	pub fn try_thunk(self, value: impl Into<Thunk<Val>>) -> Result<()> {
 		self.binding(MaybeUnbound::Bound(value.into()))
 	}
 	pub fn bindable(self, bindable: impl Unbound<Bound = Val>) -> Result<()> {
diff --git a/crates/jrsonnet-macros/src/lib.rs b/crates/jrsonnet-macros/src/lib.rs
index c154e7f..20a22f1 100644
--- a/crates/jrsonnet-macros/src/lib.rs
+++ b/crates/jrsonnet-macros/src/lib.rs
@@ -477,6 +477,7 @@ struct TypedField {
 	ident: Ident,
 	ty: Type,
 	is_option: bool,
+	is_lazy: bool,
 }
 impl TypedField {
 	fn parse(field: &syn::Field) -> Result<Self> {
@@ -503,11 +504,14 @@ impl TypedField {
 			));
 		}
 
+		let is_lazy = type_is_path(&ty, "Thunk").is_some();
+
 		Ok(Self {
 			attr,
 			ident,
 			ty,
 			is_option,
+			is_lazy,
 		})
 	}
 	/// None if this field is flattened in jsonnet output
@@ -596,21 +600,33 @@ impl TypedField {
 				} else {
 					quote! {}
 				};
-				if self.is_option {
+				let value = if self.is_lazy {
 					quote! {
-						if let Some(value) = self.#ident {
-							out.field(#name)
-								#hide
-								#add
-								.try_value(<#ty as Typed>::into_untyped(value)?)?;
-						}
+						out.field(#name)
+							#hide
+							#add
+							.try_thunk(<#ty as Typed>::into_lazy_untyped(value))?;
 					}
 				} else {
 					quote! {
 						out.field(#name)
 							#hide
 							#add
-							.try_value(<#ty as Typed>::into_untyped(self.#ident)?)?;
+							.try_value(<#ty as Typed>::into_untyped(value)?)?;
+					}
+				};
+				if self.is_option {
+					quote! {
+						if let Some(value) = self.#ident {
+							#value
+						}
+					}
+				} else {
+					quote! {
+						{
+							let value = self.#ident;
+							#value
+						}
 					}
 				}
 			},