feat: derive Eq and Hash trait for messages where possible (#1175)

Integer and bytes types can be compared using trait Eq. Some generated Rust structs can also have this property by deriving the Eq trait.

Automatically derive Eq and Hash for:
- messages that only have fields with integer or bytes types
- messages where all field types also implement Eq and Hash
- the Rust enum for one-of fields, where all fields implement Eq and Hash

Generated code for Protobuf enums already derives Eq and Hash.

BREAKING CHANGE: `prost-build` will automatically derive `trait Eq` and `trait Hash` for types where all field support those as well. If you manually `impl Eq` and/or `impl Hash` for generated types, then you need to remove the manual implementation. If you use `type_attribute` to `derive(Eq)` and/or `derive(Hash)`, then you need to remove those.

Author: caspermeijn

prost-build/src/code_generator.rs

@@ -223,12 +223,17 @@ impl<'b> CodeGenerator<'_, 'b> {
         self.append_message_attributes(&fq_message_name);
         self.push_indent();
         self.buf.push_str(&format!(
-            "#[derive(Clone, {}PartialEq, {}::Message)]\n",
+            "#[derive(Clone, {}PartialEq, {}{}::Message)]\n",
             if self.context.can_message_derive_copy(&fq_message_name) {
                 "Copy, "
             } else {
                 ""
             },
+            if self.context.can_message_derive_eq(&fq_message_name) {
+                "Eq, Hash, "
+            } else {
+                ""
+            },
             self.context.prost_path()
         ));
         self.append_skip_debug(&fq_message_name);
@@ -596,9 +601,18 @@ impl<'b> CodeGenerator<'_, 'b> {
             self.context
                 .can_field_derive_copy(fq_message_name, &field.descriptor)
         });
+        let can_oneof_derive_eq = oneof.fields.iter().all(|field| {
+            self.context
+                .can_field_derive_eq(fq_message_name, &field.descriptor)
+        });
         self.buf.push_str(&format!(
-            "#[derive(Clone, {}PartialEq, {}::Oneof)]\n",
+            "#[derive(Clone, {}PartialEq, {}{}::Oneof)]\n",
             if can_oneof_derive_copy { "Copy, " } else { "" },
+            if can_oneof_derive_eq {
+                "Eq, Hash, "
+            } else {
+                ""
+            },
             self.context.prost_path()
         ));
         self.append_skip_debug(fq_message_name);

prost-build/src/context.rs

@@ -234,6 +234,51 @@ impl<'a> Context<'a> {
         }
     }
 
+    /// Returns `true` if this message can automatically derive Eq trait.
+    pub fn can_message_derive_eq(&self, fq_message_name: &str) -> bool {
+        assert_eq!(".", &fq_message_name[..1]);
+
+        let msg = self.message_graph.get_message(fq_message_name).unwrap();
+        msg.field
+            .iter()
+            .all(|field| self.can_field_derive_eq(fq_message_name, field))
+    }
+
+    /// Returns `true` if the type of this field allows deriving the Eq trait.
+    pub fn can_field_derive_eq(&self, fq_message_name: &str, field: &FieldDescriptorProto) -> bool {
+        assert_eq!(".", &fq_message_name[..1]);
+
+        if field.r#type() == Type::Message {
+            if field.label() == Label::Repeated
+                || self
+                    .message_graph
+                    .is_nested(field.type_name(), fq_message_name)
+            {
+                false
+            } else {
+                self.can_message_derive_eq(field.type_name())
+            }
+        } else {
+            matches!(
+                field.r#type(),
+                Type::Int32
+                    | Type::Int64
+                    | Type::Uint32
+                    | Type::Uint64
+                    | Type::Sint32
+                    | Type::Sint64
+                    | Type::Fixed32
+                    | Type::Fixed64
+                    | Type::Sfixed32
+                    | Type::Sfixed64
+                    | Type::Bool
+                    | Type::Enum
+                    | Type::String
+                    | Type::Bytes
+            )
+        }
+    }
+
     pub fn should_disable_comments(&self, fq_message_name: &str, field_name: Option<&str>) -> bool {
         if let Some(field_name) = field_name {
             self.config

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

@@ -1,29 +1,29 @@
 // This file is @generated by prost-build.
-#[derive(Clone, PartialEq, ::prost::Message)]
+#[derive(Clone, PartialEq, Eq, Hash, ::prost::Message)]
 pub struct Container {
     #[prost(oneof="container::Data", tags="1, 2")]
     pub data: ::core::option::Option<container::Data>,
 }
 /// Nested message and enum types in `Container`.
 pub mod container {
-    #[derive(Clone, PartialEq, ::prost::Oneof)]
+    #[derive(Clone, PartialEq, Eq, Hash, ::prost::Oneof)]
     pub enum Data {
         #[prost(message, tag="1")]
         Foo(::prost::alloc::boxed::Box<super::Foo>),
         #[prost(message, tag="2")]
         Bar(super::Bar),
     }
 }
-#[derive(Clone, PartialEq, ::prost::Message)]
+#[derive(Clone, PartialEq, Eq, Hash, ::prost::Message)]
 pub struct Foo {
     #[prost(string, tag="1")]
     pub foo: ::prost::alloc::string::String,
 }
-#[derive(Clone, PartialEq, ::prost::Message)]
+#[derive(Clone, PartialEq, Eq, Hash, ::prost::Message)]
 pub struct Bar {
     #[prost(message, optional, boxed, tag="1")]
     pub qux: ::core::option::Option<::prost::alloc::boxed::Box<Qux>>,
 }
-#[derive(Clone, Copy, PartialEq, ::prost::Message)]
+#[derive(Clone, Copy, PartialEq, Eq, Hash, ::prost::Message)]
 pub struct Qux {
 }

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

@@ -1,28 +1,28 @@
 // This file is @generated by prost-build.
-#[derive(Clone, PartialEq, ::prost::Message)]
+#[derive(Clone, PartialEq, Eq, Hash, ::prost::Message)]
 pub struct Container {
     #[prost(oneof = "container::Data", tags = "1, 2")]
     pub data: ::core::option::Option<container::Data>,
 }
 /// Nested message and enum types in `Container`.
 pub mod container {
-    #[derive(Clone, PartialEq, ::prost::Oneof)]
+    #[derive(Clone, PartialEq, Eq, Hash, ::prost::Oneof)]
     pub enum Data {
         #[prost(message, tag = "1")]
         Foo(::prost::alloc::boxed::Box<super::Foo>),
         #[prost(message, tag = "2")]
         Bar(super::Bar),
     }
 }
-#[derive(Clone, PartialEq, ::prost::Message)]
+#[derive(Clone, PartialEq, Eq, Hash, ::prost::Message)]
 pub struct Foo {
     #[prost(string, tag = "1")]
     pub foo: ::prost::alloc::string::String,
 }
-#[derive(Clone, PartialEq, ::prost::Message)]
+#[derive(Clone, PartialEq, Eq, Hash, ::prost::Message)]
 pub struct Bar {
     #[prost(message, optional, boxed, tag = "1")]
     pub qux: ::core::option::Option<::prost::alloc::boxed::Box<Qux>>,
 }
-#[derive(Clone, Copy, PartialEq, ::prost::Message)]
+#[derive(Clone, Copy, PartialEq, Eq, Hash, ::prost::Message)]
 pub struct Qux {}

prost-build/src/fixtures/helloworld/_expected_helloworld.rs

@@ -1,14 +1,14 @@
 // This file is @generated by prost-build.
 #[derive(derive_builder::Builder)]
 #[derive(custom_proto::Input)]
-#[derive(Clone, PartialEq, ::prost::Message)]
+#[derive(Clone, PartialEq, Eq, Hash, ::prost::Message)]
 pub struct Message {
     #[prost(string, tag="1")]
     pub say: ::prost::alloc::string::String,
 }
 #[derive(derive_builder::Builder)]
 #[derive(custom_proto::Output)]
-#[derive(Clone, PartialEq, ::prost::Message)]
+#[derive(Clone, PartialEq, Eq, Hash, ::prost::Message)]
 pub struct Response {
     #[prost(string, tag="1")]
     pub say: ::prost::alloc::string::String,

prost-build/src/fixtures/helloworld/_expected_helloworld_formatted.rs

@@ -1,14 +1,14 @@
 // This file is @generated by prost-build.
 #[derive(derive_builder::Builder)]
 #[derive(custom_proto::Input)]
-#[derive(Clone, PartialEq, ::prost::Message)]
+#[derive(Clone, PartialEq, Eq, Hash, ::prost::Message)]
 pub struct Message {
     #[prost(string, tag = "1")]
     pub say: ::prost::alloc::string::String,
 }
 #[derive(derive_builder::Builder)]
 #[derive(custom_proto::Output)]
-#[derive(Clone, PartialEq, ::prost::Message)]
+#[derive(Clone, PartialEq, Eq, Hash, ::prost::Message)]
 pub struct Response {
     #[prost(string, tag = "1")]
     pub say: ::prost::alloc::string::String,

prost-types/src/compiler.rs

@@ -1,7 +1,7 @@
 // This file is @generated by prost-build.
 /// The version number of protocol compiler.
 #[cfg_attr(feature = "arbitrary", derive(arbitrary::Arbitrary))]
-#[derive(Clone, PartialEq, ::prost::Message)]
+#[derive(Clone, PartialEq, Eq, Hash, ::prost::Message)]
 pub struct Version {
     #[prost(int32, optional, tag = "1")]
     pub major: ::core::option::Option<i32>,

prost-types/src/duration.rs

@@ -1,13 +1,5 @@
 use super::*;
 
-#[cfg(feature = "std")]
-impl std::hash::Hash for Duration {
-    fn hash<H: core::hash::Hasher>(&self, state: &mut H) {
-        self.seconds.hash(state);
-        self.nanos.hash(state);
-    }
-}
-
 impl Duration {
     /// Normalizes the duration to a canonical format.
     ///

prost-types/src/protobuf.rs

@@ -94,7 +94,7 @@ pub mod descriptor_proto {
     /// fields or extension ranges in the same message. Reserved ranges may
     /// not overlap.
     #[cfg_attr(feature = "arbitrary", derive(arbitrary::Arbitrary))]
-    #[derive(Clone, Copy, PartialEq, ::prost::Message)]
+    #[derive(Clone, Copy, PartialEq, Eq, Hash, ::prost::Message)]
     pub struct ReservedRange {
         /// Inclusive.
         #[prost(int32, optional, tag = "1")]
@@ -362,7 +362,7 @@ pub mod enum_descriptor_proto {
     /// is inclusive such that it can appropriately represent the entire int32
     /// domain.
     #[cfg_attr(feature = "arbitrary", derive(arbitrary::Arbitrary))]
-    #[derive(Clone, Copy, PartialEq, ::prost::Message)]
+    #[derive(Clone, Copy, PartialEq, Eq, Hash, ::prost::Message)]
     pub struct EnumReservedRange {
         /// Inclusive.
         #[prost(int32, optional, tag = "1")]
@@ -990,7 +990,7 @@ pub mod uninterpreted_option {
     /// E.g.,{ \["foo", false\], \["bar.baz", true\], \["qux", false\] } represents
     /// "foo.(bar.baz).qux".
     #[cfg_attr(feature = "arbitrary", derive(arbitrary::Arbitrary))]
-    #[derive(Clone, PartialEq, ::prost::Message)]
+    #[derive(Clone, PartialEq, Eq, Hash, ::prost::Message)]
     pub struct NamePart {
         #[prost(string, required, tag = "1")]
         pub name_part: ::prost::alloc::string::String,
@@ -1053,7 +1053,7 @@ pub struct SourceCodeInfo {
 /// Nested message and enum types in `SourceCodeInfo`.
 pub mod source_code_info {
     #[cfg_attr(feature = "arbitrary", derive(arbitrary::Arbitrary))]
-    #[derive(Clone, PartialEq, ::prost::Message)]
+    #[derive(Clone, PartialEq, Eq, Hash, ::prost::Message)]
     pub struct Location {
         /// Identifies which part of the FileDescriptorProto was defined at this
         /// location.
@@ -1158,7 +1158,7 @@ pub struct GeneratedCodeInfo {
 /// Nested message and enum types in `GeneratedCodeInfo`.
 pub mod generated_code_info {
     #[cfg_attr(feature = "arbitrary", derive(arbitrary::Arbitrary))]
-    #[derive(Clone, PartialEq, ::prost::Message)]
+    #[derive(Clone, PartialEq, Eq, Hash, ::prost::Message)]
     pub struct Annotation {
         /// Identifies the element in the original source .proto file. This field
         /// is formatted the same as SourceCodeInfo.Location.path.
@@ -1272,7 +1272,7 @@ pub mod generated_code_info {
 /// }
 /// ```
 #[cfg_attr(feature = "arbitrary", derive(arbitrary::Arbitrary))]
-#[derive(Clone, PartialEq, ::prost::Message)]
+#[derive(Clone, PartialEq, Eq, Hash, ::prost::Message)]
 pub struct Any {
     /// A URL/resource name that uniquely identifies the type of the serialized
     /// protocol buffer message. This string must contain at least
@@ -1310,7 +1310,7 @@ pub struct Any {
 /// `SourceContext` represents information about the source of a
 /// protobuf element, like the file in which it is defined.
 #[cfg_attr(feature = "arbitrary", derive(arbitrary::Arbitrary))]
-#[derive(Clone, PartialEq, ::prost::Message)]
+#[derive(Clone, PartialEq, Eq, Hash, ::prost::Message)]
 pub struct SourceContext {
     /// The path-qualified name of the .proto file that contained the associated
     /// protobuf element.  For example: `"google/protobuf/source_context.proto"`.
@@ -1573,7 +1573,7 @@ pub struct EnumValue {
 /// A protocol buffer option, which can be attached to a message, field,
 /// enumeration, etc.
 #[cfg_attr(feature = "arbitrary", derive(arbitrary::Arbitrary))]
-#[derive(Clone, PartialEq, ::prost::Message)]
+#[derive(Clone, PartialEq, Eq, Hash, ::prost::Message)]
 pub struct Option {
     /// The option's name. For protobuf built-in options (options defined in
     /// descriptor.proto), this is the short name. For example, `"map_entry"`.
@@ -1787,7 +1787,7 @@ pub struct Method {
 /// }
 /// ```
 #[cfg_attr(feature = "arbitrary", derive(arbitrary::Arbitrary))]
-#[derive(Clone, PartialEq, ::prost::Message)]
+#[derive(Clone, PartialEq, Eq, Hash, ::prost::Message)]
 pub struct Mixin {
     /// The fully qualified name of the interface which is included.
     #[prost(string, tag = "1")]
@@ -1862,7 +1862,7 @@ pub struct Mixin {
 /// be expressed in JSON format as "3.000000001s", and 3 seconds and 1
 /// microsecond should be expressed in JSON format as "3.000001s".
 #[cfg_attr(feature = "arbitrary", derive(arbitrary::Arbitrary))]
-#[derive(Clone, Copy, PartialEq, ::prost::Message)]
+#[derive(Clone, Copy, PartialEq, Eq, Hash, ::prost::Message)]
 pub struct Duration {
     /// Signed seconds of the span of time. Must be from -315,576,000,000
     /// to +315,576,000,000 inclusive. Note: these bounds are computed from:
@@ -2101,7 +2101,7 @@ pub struct Duration {
 /// request should verify the included field paths, and return an
 /// `INVALID_ARGUMENT` error if any path is unmappable.
 #[cfg_attr(feature = "arbitrary", derive(arbitrary::Arbitrary))]
-#[derive(Clone, PartialEq, ::prost::Message)]
+#[derive(Clone, PartialEq, Eq, Hash, ::prost::Message)]
 pub struct FieldMask {
     /// The set of field mask paths.
     #[prost(string, repeated, tag = "1")]
@@ -2303,7 +2303,7 @@ impl NullValue {
 /// the time format spec '%Y-%m-%dT%H:%M:%S.%fZ'. Likewise, in Java, one can use
 /// the Joda Time's [`ISODateTimeFormat.dateTime()`](<http://www.joda.org/joda-time/apidocs/org/joda/time/format/ISODateTimeFormat.html#dateTime%2D%2D>) to obtain a formatter capable of generating timestamps in this format.
 #[cfg_attr(feature = "arbitrary", derive(arbitrary::Arbitrary))]
-#[derive(Clone, Copy, PartialEq, ::prost::Message)]
+#[derive(Clone, Copy, PartialEq, Eq, Hash, ::prost::Message)]
 pub struct Timestamp {
     /// Represents seconds of UTC time since Unix epoch
     /// 1970-01-01T00:00:00Z. Must be from 0001-01-01T00:00:00Z to

prost-types/src/timestamp.rs

@@ -123,19 +123,6 @@ impl Name for Timestamp {
     }
 }
 
-/// Implements the unstable/naive version of `Eq`: a basic equality check on the internal fields of the `Timestamp`.
-/// This implies that `normalized_ts != non_normalized_ts` even if `normalized_ts == non_normalized_ts.normalized()`.
-#[cfg(feature = "std")]
-impl Eq for Timestamp {}
-
-#[cfg(feature = "std")]
-impl std::hash::Hash for Timestamp {
-    fn hash<H: std::hash::Hasher>(&self, state: &mut H) {
-        self.seconds.hash(state);
-        self.nanos.hash(state);
-    }
-}
-
 #[cfg(feature = "std")]
 impl From<std::time::SystemTime> for Timestamp {
     fn from(system_time: std::time::SystemTime) -> Timestamp {