Support ReadableArgs types across in the TLV struct serialization

This adds `required` support for trait-wrapped reading (e.g. for
objects read via `ReadableArgs`) as well as support for the
trait-wrapped reading syntax across the TLV struct/enum
serialization macros.

Author: TheBlueMatt

lightning/src/util/ser.rs

@@ -289,17 +289,23 @@ impl<T: Readable> MaybeReadable for T {
 }
 
 /// Wrapper to read a required (non-optional) TLV record.
-pub struct RequiredWrapper<T: Readable>(pub Option<T>);
+pub struct RequiredWrapper<T>(pub Option<T>);
 impl<T: Readable> Readable for RequiredWrapper<T> {
 	#[inline]
 	fn read<R: Read>(reader: &mut R) -> Result<Self, DecodeError> {
 		Ok(Self(Some(Readable::read(reader)?)))
 	}
 }
+impl<A, T: ReadableArgs<A>> ReadableArgs<A> for RequiredWrapper<T> {
+	#[inline]
+	fn read<R: Read>(reader: &mut R, args: A) -> Result<Self, DecodeError> {
+		Ok(Self(Some(ReadableArgs::read(reader, args)?)))
+	}
+}
 /// When handling `default_values`, we want to map the default-value T directly
 /// to a `RequiredWrapper<T>` in a way that works for `field: T = t;` as
 /// well. Thus, we assume `Into<T> for T` does nothing and use that.
-impl<T: Readable> From<T> for RequiredWrapper<T> {
+impl<T> From<T> for RequiredWrapper<T> {
 	fn from(t: T) -> RequiredWrapper<T> { RequiredWrapper(Some(t)) }
 }
 

lightning/src/util/ser_macros.rs

@@ -51,6 +51,10 @@ macro_rules! _encode_tlv {
 	($stream: expr, $type: expr, $field: expr, (option, encoding: $fieldty: ty)) => {
 		$crate::_encode_tlv!($stream, $type, $field, option);
 	};
+	($stream: expr, $type: expr, $field: expr, (option: $trait: ident $(, $read_arg: expr)?)) => {
+		// Just a read-mapped type
+		$crate::_encode_tlv!($stream, $type, $field, option);
+	};
 }
 
 /// Panics if the last seen TLV type is not numerically less than the TLV type currently being checked.
@@ -161,6 +165,9 @@ macro_rules! _get_varint_length_prefixed_tlv_length {
 			$len.0 += field_len;
 		}
 	};
+	($len: expr, $type: expr, $field: expr, (option: $trait: ident $(, $read_arg: expr)?)) => {
+		$crate::_get_varint_length_prefixed_tlv_length!($len, $type, $field, option);
+	};
 	($len: expr, $type: expr, $field: expr, upgradable_required) => {
 		$crate::_get_varint_length_prefixed_tlv_length!($len, $type, $field, required);
 	};
@@ -210,6 +217,9 @@ macro_rules! _check_decoded_tlv_order {
 			return Err(DecodeError::InvalidValue);
 		}
 	}};
+	($last_seen_type: expr, $typ: expr, $type: expr, $field: ident, (required: $trait: ident $(, $read_arg: expr)?)) => {{
+		$crate::_check_decoded_tlv_order!($last_seen_type, $typ, $type, $field, required);
+	}};
 	($last_seen_type: expr, $typ: expr, $type: expr, $field: ident, option) => {{
 		// no-op
 	}};
@@ -252,6 +262,9 @@ macro_rules! _check_missing_tlv {
 			return Err(DecodeError::InvalidValue);
 		}
 	}};
+	($last_seen_type: expr, $type: expr, $field: ident, (required: $trait: ident $(, $read_arg: expr)?)) => {{
+		$crate::_check_missing_tlv!($last_seen_type, $type, $field, required);
+	}};
 	($last_seen_type: expr, $type: expr, $field: ident, vec_type) => {{
 		// no-op
 	}};
@@ -285,6 +298,9 @@ macro_rules! _decode_tlv {
 	($reader: expr, $field: ident, required) => {{
 		$field = $crate::util::ser::Readable::read(&mut $reader)?;
 	}};
+	($reader: expr, $field: ident, (required: $trait: ident $(, $read_arg: expr)?)) => {{
+		$field = $trait::read(&mut $reader $(, $read_arg)*)?;
+	}};
 	($reader: expr, $field: ident, vec_type) => {{
 		let f: $crate::util::ser::WithoutLength<Vec<_>> = $crate::util::ser::Readable::read(&mut $reader)?;
 		$field = Some(f.0);
@@ -644,6 +660,9 @@ macro_rules! _init_tlv_based_struct_field {
 	($field: ident, option) => {
 		$field
 	};
+	($field: ident, (option: $trait: ident $(, $read_arg: expr)?)) => {
+		$crate::_init_tlv_based_struct_field!($field, option)
+	};
 	($field: ident, upgradable_required) => {
 		$field.0.unwrap()
 	};
@@ -673,12 +692,18 @@ macro_rules! _init_tlv_field_var {
 	($field: ident, required) => {
 		let mut $field = $crate::util::ser::RequiredWrapper(None);
 	};
+	($field: ident, (required: $trait: ident $(, $read_arg: expr)?)) => {
+		$crate::_init_tlv_field_var!($field, required);
+	};
 	($field: ident, vec_type) => {
 		let mut $field = Some(Vec::new());
 	};
 	($field: ident, option) => {
 		let mut $field = None;
 	};
+	($field: ident, (option: $trait: ident $(, $read_arg: expr)?)) => {
+		$crate::_init_tlv_field_var!($field, option);
+	};
 	($field: ident, upgradable_required) => {
 		let mut $field = $crate::util::ser::UpgradableRequired(None);
 	};