Include Message Descriptor information

prost-build/src/code_generator.rs

@@ -123,6 +123,7 @@ impl<'a> CodeGenerator<'a> {
         debug!("  message: {:?}", message.name());
 
         let message_name = message.name().to_string();
+        let package_name = self.package.clone();
         let fq_message_name = format!(
             "{}{}.{}",
             if self.package.is_empty() { "" } else { "." },
@@ -187,6 +188,9 @@ impl<'a> CodeGenerator<'a> {
         self.buf
             .push_str("#[derive(Clone, PartialEq, ::prost::Message)]\n");
         self.push_indent();
+        self.buf
+            .push_str(format!("#[prost(package=\"{}\")]\n", package_name).as_str());
+        self.push_indent();
         self.buf.push_str("pub struct ");
         self.buf.push_str(&to_upper_camel(&message_name));
         self.buf.push_str(" {\n");

prost-derive/src/field/mod.rs

@@ -224,7 +224,7 @@ impl fmt::Display for Label {
 }
 
 /// Get the items belonging to the 'prost' list attribute, e.g. `#[prost(foo, bar="baz")]`.
-fn prost_attrs(attrs: Vec<Attribute>) -> Vec<Meta> {
+pub(crate) fn prost_attrs(attrs: Vec<Attribute>) -> Vec<Meta> {
     attrs
         .iter()
         .flat_map(Attribute::parse_meta)

prost-derive/src/lib.rs

@@ -12,11 +12,11 @@ use proc_macro2::Span;
 use quote::quote;
 use syn::{
     punctuated::Punctuated, Data, DataEnum, DataStruct, DeriveInput, Expr, Fields, FieldsNamed,
-    FieldsUnnamed, Ident, Variant,
+    FieldsUnnamed, Ident, Meta, Variant,
 };
 
 mod field;
-use crate::field::Field;
+use crate::field::{prost_attrs, Field};
 
 fn try_message(input: TokenStream) -> Result<TokenStream, Error> {
     let input: DeriveInput = syn::parse(input)?;
@@ -29,6 +29,20 @@ fn try_message(input: TokenStream) -> Result<TokenStream, Error> {
         Data::Union(..) => bail!("Message can not be derived for a union"),
     };
 
+    let pkg_name = prost_attrs(input.attrs.clone())
+        .iter()
+        .find(|meta| meta.path().is_ident("package"))
+        .and_then(|meta| match meta {
+            Meta::NameValue(v) => match &v.lit {
+                syn::Lit::Str(lit) => Some(lit.value().clone()),
+                _ => None,
+            },
+            _ => None,
+        })
+        .unwrap_or_else(|| String::from("prost"));
+
+    let type_url = format!("type.googleapis.com/{}.{}", pkg_name, ident);
+
     let generics = &input.generics;
     let (impl_generics, ty_generics, where_clause) = generics.split_for_impl();
 
@@ -204,6 +218,18 @@ fn try_message(input: TokenStream) -> Result<TokenStream, Error> {
             }
         }
 
+        impl #impl_generics ::prost::MessageDescriptor for #ident #ty_generics #where_clause {
+            fn message_name(&self) -> &'static str {
+                stringify!(#ident)
+            }
+            fn package_name(&self) -> &'static str {
+                #pkg_name
+            }
+            fn type_url(&self) -> &'static str {
+                #type_url
+            }
+        }
+
         impl #impl_generics ::core::default::Default for #ident #ty_generics #where_clause {
             fn default() -> Self {
                 #ident {

prost-types/src/compiler.rs

@@ -1,5 +1,6 @@
 /// The version number of protocol compiler.
 #[derive(Clone, PartialEq, ::prost::Message)]
+#[prost(package="google.protobuf.compiler")]
 pub struct Version {
     #[prost(int32, optional, tag="1")]
     pub major: ::core::option::Option<i32>,
@@ -14,6 +15,7 @@ pub struct Version {
 }
 /// An encoded CodeGeneratorRequest is written to the plugin's stdin.
 #[derive(Clone, PartialEq, ::prost::Message)]
+#[prost(package="google.protobuf.compiler")]
 pub struct CodeGeneratorRequest {
     /// The .proto files that were explicitly listed on the command-line.  The
     /// code generator should generate code only for these files.  Each file's
@@ -45,6 +47,7 @@ pub struct CodeGeneratorRequest {
 }
 /// The plugin writes an encoded CodeGeneratorResponse to stdout.
 #[derive(Clone, PartialEq, ::prost::Message)]
+#[prost(package="google.protobuf.compiler")]
 pub struct CodeGeneratorResponse {
     /// Error message.  If non-empty, code generation failed.  The plugin process
     /// should exit with status code zero even if it reports an error in this way.
@@ -67,6 +70,7 @@ pub struct CodeGeneratorResponse {
 pub mod code_generator_response {
     /// Represents a single generated file.
     #[derive(Clone, PartialEq, ::prost::Message)]
+    #[prost(package="google.protobuf.compiler.CodeGeneratorResponse")]
     pub struct File {
         /// The file name, relative to the output directory.  The name must not
         /// contain "." or ".." components and must be relative, not be absolute (so,