From fc3bfd9a0b3cf846bd9c3187bb1b0363611f0708 Mon Sep 17 00:00:00 2001
From: Matt Corallo <git@bluematt.me>
Date: Fri, 19 Nov 2021 20:04:36 +0000
Subject: [PATCH] Support mapping MaybeReadable

This fixes https://github.com/lightningdevkit/ldk-garbagecollected/issues/62
---
 c-bindings-gen/src/main.rs              | 21 +++++++++++++++------
 lightning-c-bindings/src/c_types/mod.rs |  3 +++
 2 files changed, 18 insertions(+), 6 deletions(-)

diff --git a/c-bindings-gen/src/main.rs b/c-bindings-gen/src/main.rs
index 1976160..4d5b070 100644
--- a/c-bindings-gen/src/main.rs
+++ b/c-bindings-gen/src/main.rs
@@ -84,9 +84,9 @@ fn maybe_convert_trait_impl<W: std::io::Write>(w: &mut W, trait_path: &syn::Path
 					writeln!(w, "}}").unwrap();
 				}
 			},
-			"lightning::util::ser::Readable"|"lightning::util::ser::ReadableArgs" => {
+			"lightning::util::ser::Readable"|"lightning::util::ser::ReadableArgs"|"lightning::util::ser::MaybeReadable" => {
 				// Create the Result<Object, DecodeError> syn::Type
-				let res_ty: syn::Type = parse_quote!(Result<#for_ty, ::ln::msgs::DecodeError>);
+				let mut res_ty: syn::Type = parse_quote!(Result<#for_ty, ::ln::msgs::DecodeError>);
 
 				writeln!(w, "#[no_mangle]").unwrap();
 				writeln!(w, "/// Read a {} from a byte array, created by {}_write", for_obj, for_obj).unwrap();
@@ -111,6 +111,8 @@ fn maybe_convert_trait_impl<W: std::io::Write>(w: &mut W, trait_path: &syn::Path
 							types.write_from_c_conversion_suffix(&mut arg_conv, &args_ty, Some(generics));
 						} else { unreachable!(); }
 					} else { unreachable!(); }
+				} else if t == "lightning::util::ser::MaybeReadable" {
+					res_ty = parse_quote!(Result<Option<#for_ty>, ::ln::msgs::DecodeError>);
 				}
 				write!(w, ") -> ").unwrap();
 				types.write_c_type(w, &res_ty, Some(generics), false);
@@ -118,12 +120,19 @@ fn maybe_convert_trait_impl<W: std::io::Write>(w: &mut W, trait_path: &syn::Path
 
 				if t == "lightning::util::ser::ReadableArgs" {
 					w.write(&arg_conv).unwrap();
-					write!(w, ";\n\tlet res: ").unwrap();
-					// At least in one case we need type annotations here, so provide them.
-					types.write_rust_type(w, Some(generics), &res_ty);
+					write!(w, ";\n").unwrap();
+				}
+
+				write!(w, "\tlet res: ").unwrap();
+				// At least in one case we need type annotations here, so provide them.
+				types.write_rust_type(w, Some(generics), &res_ty);
+
+				if t == "lightning::util::ser::ReadableArgs" {
 					writeln!(w, " = crate::c_types::deserialize_obj_arg(ser, arg_conv);").unwrap();
+				} else if t == "lightning::util::ser::MaybeReadable" {
+					writeln!(w, " = crate::c_types::maybe_deserialize_obj(ser);").unwrap();
 				} else {
-					writeln!(w, "\tlet res = crate::c_types::deserialize_obj(ser);").unwrap();
+					writeln!(w, " = crate::c_types::deserialize_obj(ser);").unwrap();
 				}
 				write!(w, "\t").unwrap();
 				if types.write_to_c_conversion_new_var(w, &format_ident!("res"), &res_ty, Some(generics), false) {
diff --git a/lightning-c-bindings/src/c_types/mod.rs b/lightning-c-bindings/src/c_types/mod.rs
index c0c44bc..3d6f08a 100644
--- a/lightning-c-bindings/src/c_types/mod.rs
+++ b/lightning-c-bindings/src/c_types/mod.rs
@@ -430,6 +430,9 @@ pub(crate) fn serialize_obj<I: lightning::util::ser::Writeable>(i: &I) -> derive
 pub(crate) fn deserialize_obj<I: lightning::util::ser::Readable>(s: u8slice) -> Result<I, lightning::ln::msgs::DecodeError> {
 	I::read(&mut s.to_slice())
 }
+pub(crate) fn maybe_deserialize_obj<I: lightning::util::ser::MaybeReadable>(s: u8slice) -> Result<Option<I>, lightning::ln::msgs::DecodeError> {
+	I::read(&mut s.to_slice())
+}
 pub(crate) fn deserialize_obj_arg<A, I: lightning::util::ser::ReadableArgs<A>>(s: u8slice, args: A) -> Result<I, lightning::ln::msgs::DecodeError> {
 	I::read(&mut s.to_slice(), args)
 }
-- 
2.30.2