Make #[non_exhaustive] for oneofs configurable

Add a configuration option to disable annotating generated enum types
for proto `oneof`s with `#[non_exhaustive]`. The annotation makes sense
for self-contained crates, but it's convenient to be able to turn it
off.

One use case is for larger projects that consist of multiple crates that
are developed together. Being unable to exhaustively match on the
contents of `oneof`s not just in the crate that includes the generated
protobuf code is very useful.

proto/rustproto.proto

@@ -19,6 +19,8 @@ extend google.protobuf.FileOptions {
     optional bool tokio_bytes_all = 17011;
     // Use `bytes::Bytes` for `string` fields
     optional bool tokio_bytes_for_string_all = 17012;
+    // When false, `#[non_exhaustive]` is not generated for `oneof` fields.
+    optional bool oneofs_non_exhaustive_all = 17013;
 
     // When true, will only generate codes that works with lite runtime.
     optional bool lite_runtime_all = 17035;
@@ -33,6 +35,8 @@ extend google.protobuf.MessageOptions {
     optional bool tokio_bytes = 17011;
     // Use `bytes::Bytes` for `string` fields
     optional bool tokio_bytes_for_string = 17012;
+    // When false, `#[non_exhaustive]` is not generated for `oneof` fields.
+    optional bool oneofs_non_exhaustive = 17013;
 }
 
 extend google.protobuf.FieldOptions {
@@ -44,4 +48,6 @@ extend google.protobuf.FieldOptions {
     optional bool tokio_bytes_field = 17011;
     // Use `bytes::Bytes` for `string` fields
     optional bool tokio_bytes_for_string_field = 17012;
+    // When false, `#[non_exhaustive]` is not generated for `oneof` fields.
+    optional bool oneofs_non_exhaustive_field = 17013;
 }

protobuf-codegen/src/customize/mod.rs

@@ -98,6 +98,8 @@ pub struct Customize {
     pub(crate) tokio_bytes: Option<bool>,
     /// Use `bytes::Bytes` for `string` fields
     pub(crate) tokio_bytes_for_string: Option<bool>,
+    /// When false, `#[non_exhaustive]` is not generated for `oneof` fields.
+    pub(crate) oneofs_non_exhaustive: Option<bool>,
     /// Enable lite runtime.
     pub(crate) lite_runtime: Option<bool>,
     /// Generate `mod.rs` in the output directory.
@@ -148,6 +150,11 @@ impl Customize {
         self
     }
 
+    pub fn oneofs_non_exhaustive(mut self, non_exhaustive: bool) -> Self {
+        self.oneofs_non_exhaustive = Some(non_exhaustive);
+        self
+    }
+
     /// Generate code for "lite runtime". Generated code contains no code for reflection.
     /// So the generated code (and more importantly, generated binary size) is smaller,
     /// but reflection, text format, JSON serialization won't work.

protobuf-codegen/src/customize/rustproto_proto.rs

@@ -12,6 +12,7 @@ pub(crate) fn customize_from_rustproto_for_message(source: &MessageOptions) -> C
     let generate_getter = rustproto::exts::generate_getter.get(source);
     let tokio_bytes = rustproto::exts::tokio_bytes.get(source);
     let tokio_bytes_for_string = rustproto::exts::tokio_bytes_for_string.get(source);
+    let oneofs_non_exhaustive = rustproto::exts::oneofs_non_exhaustive.get(source);
     let lite_runtime = None;
     let gen_mod_rs = None;
     let inside_protobuf = None;
@@ -21,6 +22,7 @@ pub(crate) fn customize_from_rustproto_for_message(source: &MessageOptions) -> C
         generate_getter,
         tokio_bytes,
         tokio_bytes_for_string,
+        oneofs_non_exhaustive,
         lite_runtime,
         gen_mod_rs,
         inside_protobuf,
@@ -37,6 +39,7 @@ pub(crate) fn customize_from_rustproto_for_field(source: &FieldOptions) -> Custo
     let generate_getter = rustproto::exts::generate_getter_field.get(source);
     let tokio_bytes = rustproto::exts::tokio_bytes_field.get(source);
     let tokio_bytes_for_string = rustproto::exts::tokio_bytes_for_string_field.get(source);
+    let oneofs_non_exhaustive = rustproto::exts::oneofs_non_exhaustive_field.get(source);
     let lite_runtime = None;
     let gen_mod_rs = None;
     let inside_protobuf = None;
@@ -46,6 +49,7 @@ pub(crate) fn customize_from_rustproto_for_field(source: &FieldOptions) -> Custo
         generate_getter,
         tokio_bytes,
         tokio_bytes_for_string,
+        oneofs_non_exhaustive,
         lite_runtime,
         gen_mod_rs,
         inside_protobuf,
@@ -58,6 +62,7 @@ pub(crate) fn customize_from_rustproto_for_file(source: &FileOptions) -> Customi
     let generate_getter = rustproto::exts::generate_getter_all.get(source);
     let tokio_bytes = rustproto::exts::tokio_bytes_all.get(source);
     let tokio_bytes_for_string = rustproto::exts::tokio_bytes_for_string_all.get(source);
+    let oneofs_non_exhaustive = rustproto::exts::oneofs_non_exhaustive_all.get(source);
     let lite_runtime = rustproto::exts::lite_runtime_all.get(source);
     let gen_mod_rs = None;
     let inside_protobuf = None;
@@ -67,6 +72,7 @@ pub(crate) fn customize_from_rustproto_for_file(source: &FileOptions) -> Customi
         generate_getter,
         tokio_bytes,
         tokio_bytes_for_string,
+        oneofs_non_exhaustive,
         lite_runtime,
         inside_protobuf,
         gen_mod_rs,

protobuf-codegen/src/gen/oneof.rs

@@ -252,7 +252,14 @@ impl<'a> OneofGen<'a> {
     fn write_enum(&self, w: &mut CodeWriter) {
         let derive = vec!["Clone", "PartialEq", "Debug"];
         w.derive(&derive);
-        w.write_line("#[non_exhaustive]");
+        if self
+            .customize
+            .for_elem
+            .oneofs_non_exhaustive
+            .unwrap_or(true)
+        {
+            w.write_line("#[non_exhaustive]");
+        }
         write_protoc_insertion_point_for_oneof(w, &self.customize.for_elem, &self.oneof.oneof);
         w.pub_enum(&self.oneof.rust_name().ident.to_string(), |w| {
             for variant in self.variants_except_group() {

protobuf-parse/src/proto/rustproto.proto

@@ -19,6 +19,8 @@ extend google.protobuf.FileOptions {
     optional bool tokio_bytes_all = 17011;
     // Use `bytes::Bytes` for `string` fields
     optional bool tokio_bytes_for_string_all = 17012;
+    // When false, `#[non_exhaustive]` is not generated for `oneof` fields.
+    optional bool oneofs_non_exhaustive_all = 17013;
 
     // When true, will only generate codes that works with lite runtime.
     optional bool lite_runtime_all = 17035;
@@ -33,6 +35,8 @@ extend google.protobuf.MessageOptions {
     optional bool tokio_bytes = 17011;
     // Use `bytes::Bytes` for `string` fields
     optional bool tokio_bytes_for_string = 17012;
+    // When false, `#[non_exhaustive]` is not generated for `oneof` fields.
+    optional bool oneofs_non_exhaustive = 17013;
 }
 
 extend google.protobuf.FieldOptions {
@@ -44,4 +48,6 @@ extend google.protobuf.FieldOptions {
     optional bool tokio_bytes_field = 17011;
     // Use `bytes::Bytes` for `string` fields
     optional bool tokio_bytes_for_string_field = 17012;
+    // When false, `#[non_exhaustive]` is not generated for `oneof` fields.
+    optional bool oneofs_non_exhaustive_field = 17013;
 }