fix: boxed string field

prost-build/src/code_generator.rs

@@ -639,21 +639,21 @@ impl CodeGenerator<'_> {
 
             self.push_indent();
             let ty_tag = self.field_type_tag(&field.descriptor);
-            self.buf.push_str(&format!(
-                "#[prost({}, tag=\"{}\")]\n",
-                ty_tag,
-                field.descriptor.number()
-            ));
-            self.append_field_attributes(&oneof_name, field.descriptor.name());
-
-            self.push_indent();
-            let ty = self.resolve_type(&field.descriptor, fq_message_name);
-
             let boxed = self.boxed(
                 &field.descriptor,
                 fq_message_name,
                 Some(oneof.descriptor.name()),
             );
+            self.buf.push_str(&format!("#[prost({}", ty_tag));
+            if boxed {
+                self.buf.push_str(", boxed");
+            }
+            self.buf
+                .push_str(&format!(", tag=\"{}\")]\n", field.descriptor.number()));
+            self.append_field_attributes(&oneof_name, field.descriptor.name());
+
+            self.push_indent();
+            let ty = self.resolve_type(&field.descriptor, fq_message_name);
 
             debug!(
                 "    oneof: {:?}, type: {:?}, boxed: {}",

prost-build/src/fixtures/field_attributes/_expected_field_attributes.rs

@@ -8,7 +8,7 @@ pub struct Container {
 pub mod container {
     #[derive(Clone, PartialEq, ::prost::Oneof)]
     pub enum Data {
-        #[prost(message, tag="1")]
+        #[prost(message, boxed, tag="1")]
         Foo(::prost::alloc::boxed::Box<super::Foo>),
         #[prost(message, tag="2")]
         Bar(super::Bar),

prost-build/src/fixtures/field_attributes/_expected_field_attributes_formatted.rs

@@ -8,7 +8,7 @@ pub struct Container {
 pub mod container {
     #[derive(Clone, PartialEq, ::prost::Oneof)]
     pub enum Data {
-        #[prost(message, tag = "1")]
+        #[prost(message, boxed, tag = "1")]
         Foo(::prost::alloc::boxed::Box<super::Foo>),
         #[prost(message, tag = "2")]
         Bar(super::Bar),

tests/build.rs

@@ -169,6 +169,7 @@ fn main() {
 
     prost_build::Config::new()
         .boxed("Foo.bar")
+        .boxed("Foo.oneof_field.box_qux")
         .compile_protos(&[src.join("boxed_field.proto")], includes)
         .unwrap();
 

tests/src/boxed_field.proto

@@ -4,6 +4,10 @@ package boxed_field;
 
 message Foo {
   Bar bar = 1;
+  oneof oneof_field {
+    string baz = 2;
+    Bar box_qux = 3;
+  }
 }
 
 message Bar {

tests/src/boxed_field.rs

@@ -1,10 +1,19 @@
 include!(concat!(env!("OUT_DIR"), "/boxed_field.rs"));
 
+cfg_if! {
+    if #[cfg(feature = "edition-2015")] {
+        use boxed_field::foo::OneofField;
+    } else {
+        use foo::OneofField;
+    }
+}
+
 #[test]
-/// Confirm `Foo::bar` is boxed by creating an instance
-fn test_bar_is_boxed() {
+/// Confirm `Foo::bar` and `OneofField::BoxQux` is boxed by creating an instance
+fn test_boxed_field() {
     use alloc::boxed::Box;
     let _ = Foo {
         bar: Some(Box::new(Bar {})),
+        oneof_field: Some(OneofField::BoxQux(Box::new(Bar {}))),
     };
 }