feat: fix bytes support

Author: Guiguiprim

prost-build/src/code_generator.rs

@@ -450,7 +450,7 @@ impl<'b> CodeGenerator<'_, 'b> {
         let type_tag = self.field_type_tag(&field.descriptor, custom_module_path.as_deref());
         self.buf.push_str(&type_tag);
 
-        if type_ == Type::Bytes {
+        if type_ == Type::Bytes && custom_module_path.is_none() {
             let bytes_type = self
                 .context
                 .bytes_type(fq_message_name, field.descriptor.name());

tests/build.rs

@@ -196,6 +196,11 @@ fn main() {
                 ".custom_scalar.Msg.g.key",
             ],
         )
+        .custom_scalar(
+            prost_types::field_descriptor_proto::Type::Bytes,
+            "crate::custom_scalar::MyVecInterface",
+            [".custom_scalar.Msg.h"],
+        )
         .compile_protos(&[src.join("custom_scalar.proto")], includes)
         .unwrap();
 

tests/src/custom_scalar.proto

@@ -13,4 +13,5 @@ message Msg {
   map<string, string> e = 5;
   map<string, string> f = 6;
   map<string, string> g = 7;
+  bytes h = 8;
 }

tests/src/custom_scalar.rs

@@ -24,6 +24,7 @@ fn test_custom_scalar() {
             .iter()
             .cloned()
             .collect(),
+        h: MyVec(vec![1, 2]),
     };
 
     let data = msg.encode_to_vec();
@@ -69,3 +70,41 @@ impl prost::CustomScalarInterface for MyStringInterface {
         }
     }
 }
+
+#[derive(Clone, Default, PartialEq, Eq, Hash, Debug, PartialOrd, Ord)]
+pub struct MyVec(pub Vec<u8>);
+
+struct MyVecInterface;
+
+impl prost::CustomScalarInterface for MyVecInterface {
+    type Type = MyVec;
+    type RefType<'x> = &'x [u8];
+
+    fn encoded_len(tag: u32, value: &Self::Type) -> usize {
+        ::prost::encoding::bytes::encoded_len(tag, &value.0)
+    }
+
+    fn encode(tag: u32, value: &Self::Type, buf: &mut impl prost::bytes::BufMut) {
+        ::prost::encoding::bytes::encode(tag, &value.0, buf);
+    }
+
+    fn merge(
+        wire_type: prost::encoding::WireType,
+        value: &mut Self::Type,
+        buf: &mut impl prost::bytes::Buf,
+        ctx: prost::encoding::DecodeContext,
+    ) -> Result<(), prost::DecodeError> {
+        ::prost::encoding::bytes::merge(wire_type, &mut value.0, buf, ctx)
+    }
+
+    fn is_default(value: &Self::Type) -> bool {
+        value.0.is_empty()
+    }
+
+    fn get<'x>(value: &'x Option<Self::Type>) -> Self::RefType<'x> {
+        match value {
+            Some(value) => value.0.as_slice(),
+            None => &[],
+        }
+    }
+}