Avoids OneOf type collision with enums and some nested types

When detecting if a oneof type will clash with other types we only
compare against nested types, and for those only the snake_case version
is validated against the oneof name. This allow room for conflicts when:
 - The collision would happen with an enum type.
 - The oneof name is a reserved word that when snaked gets sanitized as
   r#<word>.

In this change the check for collisions is updated to consider enum
types and compered against their capitalized camel case version which

Author: jknovi

prost-build/src/code_generator.rs

@@ -79,7 +79,9 @@ impl OneofField {
         let has_type_name_conflict = parent
             .nested_type
             .iter()
-            .any(|nested| to_snake(nested.name()) == descriptor.name());
+            .map(DescriptorProto::name)
+            .chain(parent.enum_type.iter().map(EnumDescriptorProto::name))
+            .any(|type_name| to_upper_camel(type_name) == to_upper_camel(descriptor.name()));
 
         Self {
             descriptor,

prost-build/src/fixtures/oneof_conflict/_oneof_conflict.rs

@@ -0,0 +1,101 @@
+// This file is @generated by prost-build.
+#[derive(Clone, PartialEq, Eq, Hash, ::prost::Message)]
+pub struct EnumAndOneOfConflict {
+    #[prost(oneof = "enum_and_one_of_conflict::TypeOneOf", tags = "1, 2, 3")]
+    pub r#type: ::core::option::Option<enum_and_one_of_conflict::TypeOneOf>,
+}
+/// Nested message and enum types in `EnumAndOneOfConflict`.
+pub mod enum_and_one_of_conflict {
+    #[derive(Clone, PartialEq, Eq, Hash, ::prost::Message)]
+    pub struct TypeOne {
+        #[prost(string, tag = "1")]
+        pub field: ::prost::alloc::string::String,
+    }
+    #[derive(Clone, Copy, PartialEq, Eq, Hash, ::prost::Message)]
+    pub struct TypeTwo {
+        #[prost(int32, tag = "1")]
+        pub field: i32,
+    }
+    #[derive(Clone, Copy, PartialEq, Eq, Hash, ::prost::Message)]
+    pub struct TypeThree {
+        #[prost(enumeration = "Type", tag = "1")]
+        pub field: i32,
+    }
+    #[derive(Clone, Copy, Debug, PartialEq, Eq, Hash, PartialOrd, Ord, ::prost::Enumeration)]
+    #[repr(i32)]
+    pub enum Type {
+        Type1 = 0,
+        Type2 = 1,
+    }
+    impl Type {
+        /// String value of the enum field names used in the ProtoBuf definition.
+        ///
+        /// The values are not transformed in any way and thus are considered stable
+        /// (if the ProtoBuf definition does not change) and safe for programmatic use.
+        pub fn as_str_name(&self) -> &'static str {
+            match self {
+                Self::Type1 => "TYPE_1",
+                Self::Type2 => "TYPE_2",
+            }
+        }
+        /// Creates an enum from field names used in the ProtoBuf definition.
+        pub fn from_str_name(value: &str) -> ::core::option::Option<Self> {
+            match value {
+                "TYPE_1" => Some(Self::Type1),
+                "TYPE_2" => Some(Self::Type2),
+                _ => None,
+            }
+        }
+    }
+    #[derive(Clone, PartialEq, Eq, Hash, ::prost::Oneof)]
+    pub enum TypeOneOf {
+        #[prost(message, tag = "1")]
+        TypeOne(TypeOne),
+        #[prost(message, tag = "2")]
+        TypeTwo(TypeTwo),
+        #[prost(message, tag = "3")]
+        TypeThree(TypeThree),
+    }
+}
+#[derive(Clone, PartialEq, Eq, Hash, ::prost::Message)]
+pub struct NestedTypeAndOneOfConflict {
+    #[prost(
+        oneof = "nested_type_and_one_of_conflict::AbstractOneOf",
+        tags = "1, 2, 3, 4"
+    )]
+    pub r#abstract: ::core::option::Option<nested_type_and_one_of_conflict::AbstractOneOf>,
+}
+/// Nested message and enum types in `NestedTypeAndOneOfConflict`.
+pub mod nested_type_and_one_of_conflict {
+    #[derive(Clone, PartialEq, Eq, Hash, ::prost::Message)]
+    pub struct Abstract {
+        #[prost(string, tag = "1")]
+        pub field: ::prost::alloc::string::String,
+    }
+    #[derive(Clone, PartialEq, Eq, Hash, ::prost::Message)]
+    pub struct TypeOne {
+        #[prost(string, tag = "1")]
+        pub field: ::prost::alloc::string::String,
+    }
+    #[derive(Clone, Copy, PartialEq, Eq, Hash, ::prost::Message)]
+    pub struct TypeTwo {
+        #[prost(int32, tag = "1")]
+        pub field: i32,
+    }
+    #[derive(Clone, PartialEq, Eq, Hash, ::prost::Message)]
+    pub struct TypeThree {
+        #[prost(message, optional, tag = "1")]
+        pub field: ::core::option::Option<Abstract>,
+    }
+    #[derive(Clone, PartialEq, Eq, Hash, ::prost::Oneof)]
+    pub enum AbstractOneOf {
+        #[prost(message, tag = "1")]
+        Abstract(Abstract),
+        #[prost(message, tag = "2")]
+        TypeOne(TypeOne),
+        #[prost(message, tag = "3")]
+        TypeTwo(TypeTwo),
+        #[prost(message, tag = "4")]
+        TypeThree(TypeThree),
+    }
+}

prost-build/src/fixtures/oneof_conflict/oneof_conflict.proto

@@ -0,0 +1,34 @@
+syntax = "proto3";
+
+package oneof_conflict;
+
+message EnumAndOneOfConflict {
+  enum Type {
+    TYPE_1 = 0;
+    TYPE_2 = 1;
+  }
+
+  message TypeOne { string field = 1; }
+  message TypeTwo { int32 field = 1; }
+  message TypeThree { Type field = 1; }
+
+  oneof type {
+    TypeOne type_one = 1;
+    TypeTwo type_two = 2;
+    TypeThree type_three = 3;
+  }
+}
+
+message NestedTypeAndOneOfConflict {
+  message Abstract { string field = 1; }
+  message TypeOne { string field = 1; }
+  message TypeTwo { int32 field = 1; }
+  message TypeThree { Abstract field = 1; }
+
+  oneof abstract {
+    Abstract abstract_ = 1;
+    TypeOne type_one = 2;
+    TypeTwo type_two = 3;
+    TypeThree type_three = 4;
+  }
+}

prost-build/src/lib.rs

@@ -597,4 +597,23 @@ mod tests {
             tempdir.path().join("all_deprecated.rs")
         );
     }
+
+    #[test]
+    fn test_oneof_conflict() {
+        let _ = env_logger::try_init();
+        let tempdir = tempfile::tempdir().unwrap();
+
+        Config::new()
+            .out_dir(tempdir.path())
+            .compile_protos(
+                &["src/fixtures/oneof_conflict/oneof_conflict.proto"],
+                &["src/fixtures/oneof_conflict"],
+            )
+            .unwrap();
+
+        assert_eq_fixture_file!(
+            "src/fixtures/oneof_conflict/_oneof_conflict.rs",
+            tempdir.path().join("oneof_conflict.rs")
+        );
+    }
 }