feat: Add OneofDescriptor::is_synthetic

prost-reflect-build/src/lib.rs

@@ -152,14 +152,10 @@ impl Builder {
         let descriptor = DescriptorPool::decode(buf.as_ref()).expect("Invalid file descriptor");
 
         let pool_attribute = if let Some(descriptor_pool) = &self.descriptor_pool_expr {
-            format!(
-                r#"#[prost_reflect(descriptor_pool = "{}")]"#,
-                descriptor_pool,
-            )
+            format!(r#"#[prost_reflect(descriptor_pool = "{descriptor_pool}")]"#,)
         } else if let Some(file_descriptor_set_bytes) = &self.file_descriptor_set_bytes_expr {
             format!(
-                r#"#[prost_reflect(file_descriptor_set_bytes = "{}")]"#,
-                file_descriptor_set_bytes,
+                r#"#[prost_reflect(file_descriptor_set_bytes = "{file_descriptor_set_bytes}")]"#,
             )
         } else {
             return Err(io::Error::other(
@@ -173,7 +169,7 @@ impl Builder {
                 .type_attribute(full_name, "#[derive(::prost_reflect::ReflectMessage)]")
                 .type_attribute(
                     full_name,
-                    format!(r#"#[prost_reflect(message_name = "{}")]"#, full_name,),
+                    format!(r#"#[prost_reflect(message_name = "{full_name}")]"#),
                 )
                 .type_attribute(full_name, &pool_attribute);
         }

prost-reflect-conformance-tests/build.rs

@@ -19,10 +19,10 @@ fn main() -> Result<()> {
     }
 
     let version = git_describe(&src_dir)?;
-    let protobuf_dir = &out_dir.join(format!("protobuf-{}", version));
+    let protobuf_dir = &out_dir.join(format!("protobuf-{version}"));
 
     if !protobuf_dir.exists() {
-        let build_dir = &out_dir.join(format!("build-protobuf-{}", version));
+        let build_dir = &out_dir.join(format!("build-protobuf-{version}"));
         fs::create_dir_all(build_dir).expect("failed to create build directory");
 
         let tempdir = tempfile::Builder::new()

prost-reflect-conformance-tests/src/main.rs

@@ -37,7 +37,7 @@ fn main() -> io::Result<()> {
 
         let result = match ConformanceRequest::decode(&*bytes) {
             Ok(request) => handle_request(request),
-            Err(error) => conformance_response::Result::ParseError(format!("{:?}", error)),
+            Err(error) => conformance_response::Result::ParseError(format!("{error:?}")),
         };
 
         let response = ConformanceResponse {

prost-reflect-tests/src/arbitrary.rs

@@ -68,7 +68,7 @@ pub fn mask() -> impl Strategy<Value = FieldMask> {
                 let mut parts = parts.into_iter();
                 let mut path = parts.next().unwrap();
                 for part in parts {
-                    write!(path, ".{}", part).unwrap();
+                    write!(path, ".{part}").unwrap();
                 }
                 path
             })

prost-reflect-tests/src/desc.rs

@@ -243,35 +243,35 @@ fn test_debug_impls() {
     let _ = format!("{:?}", test_file_descriptor());
 
     for service in test_file_descriptor().services() {
-        let _ = format!("{:?}", service);
+        let _ = format!("{service:?}");
         for method in service.methods() {
-            let _ = format!("{:?}", method);
+            let _ = format!("{method:?}");
         }
     }
 
     for file in test_file_descriptor().files() {
-        let _ = format!("{:?}", file);
+        let _ = format!("{file:?}");
     }
 
     for message in test_file_descriptor().all_messages() {
-        let _ = format!("{:?}", message);
+        let _ = format!("{message:?}");
         for field in message.fields() {
-            let _ = format!("{:?}", field);
+            let _ = format!("{field:?}");
         }
         for oneof in message.oneofs() {
-            let _ = format!("{:?}", oneof);
+            let _ = format!("{oneof:?}");
         }
     }
 
     for enum_ in test_file_descriptor().all_enums() {
-        let _ = format!("{:?}", enum_);
+        let _ = format!("{enum_:?}");
         for value in enum_.values() {
-            let _ = format!("{:?}", value);
+            let _ = format!("{value:?}");
         }
     }
 
     for extension in test_file_descriptor().all_extensions() {
-        let _ = format!("{:?}", extension);
+        let _ = format!("{extension:?}");
     }
 }
 
@@ -785,3 +785,33 @@ fn message_take_fields() {
     assert_eq!(dynamic_message.fields_mut().count(), 0);
     assert_eq!(dynamic_message.extensions_mut().count(), 0);
 }
+
+#[test]
+fn oneof_not_synthetic() {
+    let message_desc = test_file_descriptor()
+        .get_message_by_name("test.MessageWithOneof")
+        .unwrap();
+
+    assert_eq!(message_desc.oneofs().len(), 1);
+
+    let oneof_desc = message_desc.oneofs().next().unwrap();
+    assert_eq!(oneof_desc.name(), "test_oneof");
+    assert!(!oneof_desc.is_synthetic());
+}
+
+#[test]
+fn proto3_optional_field() {
+    let message_desc = test_file_descriptor()
+        .get_message_by_name("test.MessageWithOptionalEnum")
+        .unwrap();
+    let field_desc = message_desc.get_field_by_name("optional_enum").unwrap();
+    let oneof_desc = field_desc.containing_oneof().unwrap();
+
+    assert!(field_desc.supports_presence());
+    assert_eq!(oneof_desc.name(), "_optional_enum");
+    assert!(oneof_desc.is_synthetic());
+    assert!(oneof_desc.fields().eq([field_desc.clone()]));
+
+    assert_eq!(message_desc.oneofs().len(), 1);
+    assert!(message_desc.oneofs().eq([oneof_desc.clone()]));
+}

prost-reflect-tests/src/test.proto

@@ -89,6 +89,14 @@ message MessageWithOneof {
   }
 }
 
+message MessageWithOptionalEnum {
+  enum OptionalEnum {
+    DEFAULT = 0;
+  }
+
+  optional OptionalEnum optional_enum = 1;
+}
+
 message Point {
   int32 latitude = 1;
   int32 longitude = 2;

prost-reflect/src/descriptor/api.rs

@@ -1610,6 +1610,16 @@ impl OneofDescriptor {
         })
     }
 
+    /// Returns `true` if this is a synthetic oneof generated to support proto3 optional semantics.
+    ///
+    /// If `true`, then [`fields`](OneofDescriptor::fields) will yield exactly one field, for which [`FieldDescriptorProto::proto3_optional`] returns true.
+    pub fn is_synthetic(&self) -> bool {
+        self.fields().len() == 1
+            && self
+                .fields()
+                .all(|f| f.field_descriptor_proto().proto3_optional())
+    }
+
     fn inner(&self) -> &OneofDescriptorInner {
         &self.message.inner().oneofs[self.index as usize]
     }
@@ -1882,7 +1892,7 @@ fn join_name<'a>(namespace: &str, name: &'a str) -> Cow<'a, str> {
     if namespace.is_empty() {
         Cow::Borrowed(name)
     } else {
-        Cow::Owned(format!("{}.{}", namespace, name))
+        Cow::Owned(format!("{namespace}.{name}"))
     }
 }
 

prost-reflect/src/descriptor/build/mod.rs

@@ -263,8 +263,7 @@ impl<'a, 'b> ResolveNameResult<'a, 'b> {
                         join_path(found_path1, found_path2),
                     ),
                     help: Some(format!(
-                        "'{}' is defined in '{}', which is not imported by '{}'",
-                        name, dep_name, root_name
+                        "'{name}' is defined in '{dep_name}', which is not imported by '{root_name}'"
                     )),
                     name: name.into_owned(),
                 })
@@ -341,7 +340,7 @@ fn resolve_relative_name<'a, 'b>(
     for candidate_parent in resolve_relative_candidate_parents(scope) {
         let candidate = match candidate_parent {
             "" => Cow::Borrowed(relative_first_part),
-            _ => Cow::Owned(format!("{}.{}", candidate_parent, relative_first_part)),
+            _ => Cow::Owned(format!("{candidate_parent}.{relative_first_part}")),
         };
 
         if relative_first_part.len() == relative_name.len() {
@@ -358,7 +357,7 @@ fn resolve_relative_name<'a, 'b>(
                 Some(def) if def.kind.is_parent() => {
                     let candidate_full = match candidate_parent {
                         "" => Cow::Borrowed(relative_name),
-                        _ => Cow::Owned(format!("{}.{}", candidate_parent, relative_name)),
+                        _ => Cow::Owned(format!("{candidate_parent}.{relative_name}")),
                     };
 
                     let res =

prost-reflect/src/descriptor/build/options.rs

@@ -744,7 +744,7 @@ fn set_file_option(file: &mut FileDescriptorProto, path: &[i32], encoded: &[u8])
                     let value = &mut service.method[path[3] as usize];
                     value.options = Some(Options::decode(encoded).unwrap());
                 }
-                p => panic!("unknown path element {}", p),
+                p => panic!("unknown path element {p}"),
             }
         }
         tag::file::EXTENSION => {
@@ -753,7 +753,7 @@ fn set_file_option(file: &mut FileDescriptorProto, path: &[i32], encoded: &[u8])
             let field = &mut file.extension[path[1] as usize];
             field.options = Some(Options::decode(encoded).unwrap());
         }
-        p => panic!("unknown path element {}", p),
+        p => panic!("unknown path element {p}"),
     }
 }
 
@@ -795,7 +795,7 @@ fn set_message_option(message: &mut DescriptorProto, path: &[i32], encoded: &[u8
             let field = &mut message.extension[path[1] as usize];
             field.options = Some(Options::decode(encoded).unwrap());
         }
-        p => panic!("unknown path element {}", p),
+        p => panic!("unknown path element {p}"),
     }
 }
 
@@ -808,6 +808,6 @@ fn set_enum_option(enum_: &mut EnumDescriptorProto, path: &[i32], encoded: &[u8]
             let value = &mut enum_.value[path[1] as usize];
             value.options = Some(Options::decode(encoded).unwrap());
         }
-        p => panic!("unknown path element {}", p),
+        p => panic!("unknown path element {p}"),
     }
 }

prost-reflect/src/descriptor/build/resolve.rs

@@ -404,7 +404,7 @@ impl Visitor for ResolveVisitor<'_> {
             id: Identity::new(file, path, full_name, extension.name()),
             parent: parent_message,
             number: extension.number() as u32,
-            json_name: format!("[{}]", full_name).into(),
+            json_name: format!("[{full_name}]").into(),
             extendee: extendee.unwrap_or(MessageIndex::MAX),
             kind: kind.unwrap_or(KindIndex::Double),
             is_packed,
@@ -653,7 +653,7 @@ impl ResolveVisitor<'_> {
                 Err(_) => {
                     self.errors.push(DescriptorErrorKind::InvalidFieldDefault {
                         value: default_value.to_owned(),
-                        kind: format!("{:?}", kind),
+                        kind: format!("{kind:?}"),
                         found: Label::new(
                             &self.pool.files,
                             "found here",
@@ -753,7 +753,7 @@ impl ResolveVisitor<'_> {
             &mut self.pool.files[file as usize].raw,
             path,
             tag,
-            format!(".{}", type_name),
+            format!(".{type_name}"),
             ty,
         );
         Some(def)
@@ -899,7 +899,7 @@ fn set_type_name(
             match tag {
                 tag::method::INPUT_TYPE => method.input_type = Some(type_name),
                 tag::method::OUTPUT_TYPE => method.output_type = Some(type_name),
-                p => panic!("unknown path element {}", p),
+                p => panic!("unknown path element {p}"),
             }
         }
         tag::file::MESSAGE_TYPE | tag::file::EXTENSION => {
@@ -912,10 +912,10 @@ fn set_type_name(
                     }
                 }
                 tag::field::EXTENDEE => field.extendee = Some(type_name),
-                p => panic!("unknown path element {}", p),
+                p => panic!("unknown path element {p}"),
             }
         }
-        p => panic!("unknown path element {}", p),
+        p => panic!("unknown path element {p}"),
     }
 }
 
@@ -932,7 +932,7 @@ fn find_file_field_proto_mut<'a>(
             debug_assert_eq!(path.len(), 2);
             &mut file.extension[path[1] as usize]
         }
-        p => panic!("unknown path element {}", p),
+        p => panic!("unknown path element {p}"),
     }
 }
 
@@ -953,7 +953,7 @@ fn find_message_field_proto<'a>(
             let nested_message = &mut message.nested_type[path[1] as usize];
             find_message_field_proto(nested_message, &path[2..])
         }
-        p => panic!("unknown path element {}", p),
+        p => panic!("unknown path element {p}"),
     }
 }