fix enum setters in the presence of defaults

Author: dwrensha

capnpc/src/codegen.rs

@@ -1006,9 +1006,20 @@ fn generate_setter(
                 type_::Enum(e) => {
                     let id = e.get_type_id();
                     let the_mod = ctx.get_qualified_module(id);
-                    setter_interior.push(Line(format!(
-                        "self.builder.set_data_field::<u16>({offset}, value as u16)"
-                    )));
+                    if !reg_field.get_had_explicit_default() {
+                        setter_interior.push(Line(format!(
+                            "self.builder.set_data_field::<u16>({offset}, value as u16);"
+                        )));
+                    } else {
+                        match reg_field.get_default_value()?.which()? {
+                            schema_capnp::value::Enum(d) => {
+                                setter_interior.push(Line(format!(
+                                    "self.builder.set_data_field_mask::<u16>({offset}, value as u16, {d});"
+                                )));
+                            }
+                            _ => return Err(Error::failed("enum default not an Enum".to_string())),
+                        }
+                    };
                     (Some(the_mod), None)
                 }
                 type_::Struct(_) => {

capnpc/test/test.rs

@@ -492,7 +492,7 @@ mod tests {
 
     #[test]
     fn test_defaults() {
-        use crate::test_capnp::test_defaults;
+        use crate::test_capnp::{test_defaults, TestEnum};
 
         {
             let message = message::Builder::new_default();
@@ -524,6 +524,7 @@ mod tests {
             test_defaults.set_u_int64_field(123456789012345);
             test_defaults.set_float32_field(7890.123);
             test_defaults.set_float64_field(5e55);
+            test_defaults.set_enum_field(TestEnum::Baz);
 
             {
                 let mut sub_builder = test_defaults.reborrow().get_struct_field().unwrap();
@@ -544,6 +545,10 @@ mod tests {
             );
             assert_eq!(test_defaults.reborrow().get_float32_field(), 7890.123);
             assert_eq!(test_defaults.reborrow().get_float64_field(), 5e55);
+            assert_eq!(
+                test_defaults.reborrow().get_enum_field().unwrap(),
+                TestEnum::Baz
+            );
 
             {
                 let sub_builder = test_defaults.reborrow().get_struct_field().unwrap();