Generate rustdocs from .proto file comments (#10)

* generate rustdoc comments from .proto file comments

* move imports to top of file

tonic-build/src/client.rs

@@ -1,3 +1,4 @@
+use crate::generate_doc_comments;
 use proc_macro2::TokenStream;
 use prost_build::{Method, Service};
 use quote::{format_ident, quote};
@@ -8,8 +9,10 @@ pub(crate) fn generate(service: &Service, proto: &str) -> TokenStream {
     let methods = generate_methods(service, proto);
 
     let connect = generate_connect(&service_ident);
+    let service_doc = generate_doc_comments(&service.comments.leading);
 
     quote! {
+        #service_doc
         pub struct #service_ident<T> {
             inner: tonic::client::Grpc<T>,
         }
@@ -75,6 +78,8 @@ fn generate_methods(service: &Service, proto: &str) -> TokenStream {
             service.package, service.proto_name, method.proto_name
         );
 
+        stream.extend(generate_doc_comments(&method.comments.leading));
+
         let method = match (method.client_streaming, method.server_streaming) {
             (false, false) => generate_unary(method, &proto, path),
             (false, true) => generate_server_streaming(method, &proto, path),

tonic-build/src/lib.rs

@@ -25,8 +25,9 @@
 //! }
 //! ```
 
-use proc_macro2::TokenStream;
+use proc_macro2::{TokenStream, Delimiter, Group, Ident, Literal, Punct, Spacing, Span};
 use prost_build::Config;
+use quote::TokenStreamExt;
 
 #[cfg(feature = "rustfmt")]
 use std::process::Command;
@@ -199,3 +200,28 @@ impl prost_build::ServiceGenerator for ServiceGenerator {
         }
     }
 }
+
+// Generate a singular line of a doc comment
+fn generate_doc_comment(comment: &str, stream: &mut TokenStream) {
+    let mut doc_stream = TokenStream::new();
+
+    doc_stream.append(Ident::new("doc", Span::call_site()));
+    doc_stream.append(Punct::new('=', Spacing::Alone));
+    doc_stream.append(Literal::string(&comment));
+
+    let group = Group::new(Delimiter::Bracket, doc_stream);
+
+    stream.append(Punct::new('#', Spacing::Alone));
+    stream.append(group);
+}
+
+// Generate a larger doc comment composed of many lines of doc comments
+fn generate_doc_comments<T: AsRef<str>>(comments: &[T]) -> TokenStream {
+    let mut stream = TokenStream::new();
+
+    for comment in comments {
+        generate_doc_comment(comment.as_ref(), &mut stream);
+    }
+
+    stream
+}

tonic-build/src/service.rs

@@ -1,3 +1,4 @@
+use crate::generate_doc_comments;
 use proc_macro2::{Span, TokenStream};
 use prost_build::{Method, Service};
 use quote::quote;
@@ -10,10 +11,12 @@ pub(crate) fn generate(service: &Service, proto_path: &str) -> TokenStream {
     let server_service = quote::format_ident!("{}ServerSvc", service.name);
     let server_trait = quote::format_ident!("{}", service.name);
     let generated_trait = generate_trait(service, proto_path, server_trait.clone());
+    let service_doc = generate_doc_comments(&service.comments.leading);
 
     quote! {
         #generated_trait
 
+        #service_doc
         #[derive(Clone, Debug)]
         pub struct #server_make_service<T: #server_trait> {
             inner: Arc<T>,