Skip empty attributes

3 files changed, 51 insertions, 14 deletions

diff --git a/src/document_tree/attribute_types.rs b/src/document_tree/attribute_types.rs
index 400c59e..1648c18 100644
--- a/src/document_tree/attribute_types.rs
+++ b/src/document_tree/attribute_types.rs
@@ -4,6 +4,8 @@ use failure::{Error,bail,format_err};
 use serde_derive::Serialize;
 use regex::Regex;
 
+use crate::target;
+
 #[derive(Debug,PartialEq,Serialize)]
 pub enum EnumeratedListType {
 	Arabic,
@@ -96,3 +98,42 @@ mod test {
 		let _d: Measure = "1.pc".parse().unwrap();
 	}
 }
+
+pub(crate) trait CanBeEmpty {
+	fn is_empty(&self) -> bool;
+}
+
+/* Specialization necessary
+impl<T> CanBeEmpty for T {
+	fn is_empty(&self) -> bool { false }
+}
+*/
+macro_rules! impl_cannot_be_empty {
+	($t:ty) => {
+		impl CanBeEmpty for $t {
+			fn is_empty(&self) -> bool { false }
+		}
+	};
+	($t:ty, $($ts:ty),*) => {
+		impl_cannot_be_empty!($t);
+		impl_cannot_be_empty!($($ts),*);
+	};
+}
+impl_cannot_be_empty!(target::Target);
+
+impl<T> CanBeEmpty for Option<T> {
+	fn is_empty(&self) -> bool { self.is_none() }
+}
+
+impl<T> CanBeEmpty for Vec<T> {
+	fn is_empty(&self) -> bool { self.is_empty() }
+}
+
+impl CanBeEmpty for bool {
+	fn is_empty(&self) -> bool { !self }
+}
+
+impl CanBeEmpty for FixedSpace {
+	fn is_empty(&self) -> bool { self == &FixedSpace::default() }
+}
+
diff --git a/src/document_tree/elements.rs b/src/document_tree/elements.rs
index 52b1f5b..fe5a498 100644
--- a/src/document_tree/elements.rs
+++ b/src/document_tree/elements.rs
@@ -1,7 +1,7 @@
 use serde_derive::Serialize;
 
 use crate::target;
-use super::attribute_types::{ID,NameToken};
+use super::attribute_types::{CanBeEmpty,ID,NameToken};
 use super::extra_attributes::{self,ExtraAttributes};
 use super::element_categories::*;
 
@@ -28,9 +28,13 @@ pub trait Element {
 
 #[derive(Debug,Default,PartialEq,Serialize)]
 pub struct CommonAttributes {
-	ids:     Vec<ID>,
-	names:   Vec<NameToken>,
-	source:  Option<target::Target>,
+	#[serde(skip_serializing_if = "CanBeEmpty::is_empty")]
+	ids: Vec<ID>,
+	#[serde(skip_serializing_if = "CanBeEmpty::is_empty")]
+	names: Vec<NameToken>,
+	#[serde(skip_serializing_if = "CanBeEmpty::is_empty")]
+	source: Option<target::Target>,
+	#[serde(skip_serializing_if = "CanBeEmpty::is_empty")]
 	classes: Vec<String>,
 	//TODO: dupnames
 }
diff --git a/src/document_tree/extra_attributes.rs b/src/document_tree/extra_attributes.rs
index 0708080..d73cdec 100644
--- a/src/document_tree/extra_attributes.rs
+++ b/src/document_tree/extra_attributes.rs
@@ -1,7 +1,7 @@
 use serde_derive::Serialize;
 
 use crate::target;
-use super::attribute_types::{FixedSpace,ID,NameToken,AlignHV,AlignH,Measure,EnumeratedListType};
+use super::attribute_types::{CanBeEmpty,FixedSpace,ID,NameToken,AlignHV,AlignH,Measure,EnumeratedListType};
 
 pub trait ExtraAttributes<A> {
 	fn with_extra(extra: A) -> Self;
@@ -9,14 +9,6 @@ pub trait ExtraAttributes<A> {
 	fn extra_mut(&mut self) -> &mut A;
 }
 
-/*
-macro_rules! skip {
-	(Option<$type:ty>) => { #[serde(skip_serializing_if = "Option::is_none")] };
-	(Vec   <$type:ty>) => { #[serde(skip_serializing_if = "Vec::is_empty"  )] };
-	(bool            ) => { #[serde(skip_serializing_if = "Not::not"       )] };
-}
-*/
-
 macro_rules! impl_extra {
 	( $name:ident { $( $(#[$pattr:meta])* $param:ident : $type:ty ),* $(,)* } ) => (
 		impl_extra!(
@@ -28,7 +20,7 @@ macro_rules! impl_extra {
 		$(#[$attr])+
 		pub struct $name { $(
 			$(#[$pattr])*
-			// skip!($type)
+			#[serde(skip_serializing_if = "CanBeEmpty::is_empty")]
 			pub $param : $type,
 		)* }
 	);