From 1ba7e85dfc32b372d55870d2e2de923420aa33d1 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Sosth=C3=A8ne=20Gu=C3=A9don?= <sosthene@nitrokey.com>
Date: Mon, 24 Jun 2024 16:40:03 +0200
Subject: [PATCH] Implement serialize_with

---
 Cargo.toml      |  2 +-
 src/lib.rs      | 30 ++++++++++++++++++++++++++++--
 src/parse.rs    |  2 ++
 tests/basics.rs | 22 ++++++++++++++++++++++
 4 files changed, 53 insertions(+), 3 deletions(-)

diff --git a/Cargo.toml b/Cargo.toml
index b2d4684..f8d0b1e 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -23,6 +23,6 @@ heapless = { version = "0.7.16", default-features = false, features = ["serde"]
 hex-literal = "0.4.1"
 serde = { version = "1" }
 serde-byte-array = "0.1.2"
-serde_bytes = { version = "0.11.12", default-features = false }
+serde_bytes = { version = "0.11.12" }
 serde_cbor = { version = "0.11.0" }
 serde_test = "1.0.176"
diff --git a/src/lib.rs b/src/lib.rs
index 360dc7c..dee75ad 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -44,16 +44,42 @@ fn serialize_fields(fields: &[parse::Field], offset: usize) -> Vec<proc_macro2::
         .filter_map(|field| {
             let index = field.index + offset;
             let member = &field.member;
+            let serialize_member = match &field.serialize_with {
+                None => quote!(&self.#member),
+                Some(f) => {
+                    let ty = &field.ty;
+                    quote!({
+                            struct __SerializeWith<'__lifetime> {
+                                value: &'__lifetime #ty,
+                            }
+
+                            impl<'__lifetime> serde::Serialize for __SerializeWith<'__lifetime> {
+                                fn serialize<__S>(
+                                    &self,
+                                    __s: __S,
+                                ) -> ::core::result::Result<__S::Ok, __S::Error>
+                                where
+                                    __S: serde::Serializer,
+                                {
+                                    #f(self.value, __s)
+                                }
+                            }
+
+                            &__SerializeWith { value: &self.#member }
+                    })
+                }
+            };
+
             // println!("field {:?} index {:?}", &field.label, field.index);
             match &field.skip_serializing_if {
                 Skip::If(path) => Some(quote! {
                     if !#path(&self.#member) {
-                        map.serialize_entry(&#index, &self.#member)?;
+                        map.serialize_entry(&#index, #serialize_member)?;
                     }
                 }),
                 Skip::Always => None,
                 Skip::Never => Some(quote! {
-                    map.serialize_entry(&#index, &self.#member)?;
+                    map.serialize_entry(&#index, #serialize_member)?;
                 }),
             }
         })
diff --git a/src/parse.rs b/src/parse.rs
index 96c0f55..f5e51fe 100644
--- a/src/parse.rs
+++ b/src/parse.rs
@@ -38,6 +38,7 @@ pub struct Field {
     pub skip_serializing_if: Skip,
     pub serialize_with: Option<syn::ExprPath>,
     pub deserialize_with: Option<syn::ExprPath>,
+    pub ty: syn::Type,
 }
 
 fn parse_meta(attrs: &mut StructAttrs, meta: ParseNestedMeta) -> Result<()> {
@@ -190,6 +191,7 @@ fn fields_from_ast(
                 },
                 index: current_index,
                 // TODO: make this... more concise? handle errors? the thing with the spans?
+                ty: field.ty.clone(),
                 skip_serializing_if,
                 serialize_with,
                 deserialize_with,
diff --git a/tests/basics.rs b/tests/basics.rs
index 26f3c04..97f0d7e 100644
--- a/tests/basics.rs
+++ b/tests/basics.rs
@@ -418,6 +418,7 @@ mod generics {
     use heapless::String;
     use serde_byte_array::ByteArray;
     use serde_bytes::Bytes;
+    use serde_test::assert_ser_tokens;
 
     #[derive(PartialEq, Debug, SerializeIndexed, DeserializeIndexed)]
     #[serde_indexed(offset = 1)]
@@ -522,4 +523,25 @@ mod generics {
 
         assert_eq!(deserialized, example);
     }
+
+    #[test]
+    fn serialize_with() {
+        #[derive(serde_indexed::SerializeIndexed)]
+        struct SerializeWith {
+            #[serde(serialize_with = "serde_bytes::serialize")]
+            data: Vec<u8>,
+        }
+
+        let value = SerializeWith { data: vec![0; 128] };
+
+        assert_ser_tokens(
+            &value,
+            &[
+                Token::Map { len: Some(1) },
+                Token::U64(0),
+                Token::Bytes(&[0; 128]),
+                Token::MapEnd,
+            ],
+        )
+    }
 }