gen_mod_rs codegen option

When this option is specified, codegens generate `mod.rs` which
`pub use` all the generated files.

This way:
* users can include generated files
* users don't have to enumerate generated files
* this opens door to generating mod hierarchy

protobuf-codegen-pure-test/build.rs

@@ -9,6 +9,7 @@ extern crate protobuf_test_common;
 use std::io::Read;
 use std::io::Write;
 
+use std::env;
 use std::fs;
 use std::path::Path;
 
@@ -20,7 +21,7 @@ fn copy_test<P1: AsRef<Path>, P2: AsRef<Path>>(src: P1, dst: P2) {
     fs::File::open(src.as_ref())
         .expect(&format!("open {}", src.as_ref().display()))
         .read_to_end(&mut content)
-        .expect("read_to_end");
+        .expect(&format!("read_to_end {}", src.as_ref().display()));
 
     let mut write = fs::File::create(dst).expect("create");
     writeln!(write, "// @generated").expect("write");
@@ -120,6 +121,27 @@ fn generate_interop() {
         .unwrap();
 }
 
+fn generate_include_generated() {
+    copy_from_protobuf_test("src/include_generated/mod.rs");
+
+    let dir = format!("{}/include_generated", env::var("OUT_DIR").unwrap());
+    if Path::new(&dir).exists() {
+        fs::remove_dir_all(&dir).unwrap();
+    }
+    fs::create_dir(&dir).unwrap();
+    protobuf_codegen_pure::Codegen::new()
+        .out_dir(dir)
+        .input("../protobuf-test/src/include_generated/v2.proto")
+        .input("../protobuf-test/src/include_generated/v3.proto")
+        .customize(Customize {
+            gen_mod_rs: Some(true),
+            ..Default::default()
+        })
+        .include("../protobuf-test/src/include_generated")
+        .run()
+        .unwrap();
+}
+
 fn generate_pb_rs() {
     print_rerun_if_changed("../protobuf-test");
 
@@ -139,6 +161,8 @@ fn generate_pb_rs() {
     gen_in_dir("src/google/protobuf", "src");
 
     generate_interop();
+
+    generate_include_generated();
 }
 
 fn main() {

protobuf-codegen-pure-test/src/include_generated/.gitignore

@@ -0,0 +1 @@
+*

protobuf-codegen-pure-test/src/lib.rs

@@ -21,3 +21,5 @@ mod v3;
 mod common;
 
 mod interop;
+
+mod include_generated;

protobuf-codegen/src/customize.rs

@@ -26,6 +26,12 @@ pub struct Customize {
     pub serde_derive_cfg: Option<String>,
     /// Enable lite runtime
     pub lite_runtime: Option<bool>,
+    /// Generate `mod.rs` in the output directory.
+    ///
+    /// This option allows inclusion of generated files from cargo output directory.
+    ///
+    /// This option will likely be on by default in rust-protobuf version 3.
+    pub gen_mod_rs: Option<bool>,
     /// Used internally to generate protos bundled in protobuf crate
     /// like `descriptor.proto`
     pub inside_protobuf: Option<bool>,
@@ -75,6 +81,9 @@ impl Customize {
         if let Some(v) = that.lite_runtime {
             self.lite_runtime = Some(v);
         }
+        if let Some(v) = that.gen_mod_rs {
+            self.gen_mod_rs = Some(v);
+        }
         if let Some(v) = that.inside_protobuf {
             self.inside_protobuf = Some(v);
         }
@@ -122,6 +131,8 @@ impl Customize {
                 r.serde_derive_cfg = Some(v.to_owned());
             } else if n == "lite_runtime" {
                 r.lite_runtime = Some(parse_bool(v)?);
+            } else if n == "gen_mod_rs" {
+                r.gen_mod_rs = Some(parse_bool(v)?);
             } else if n == "inside_protobuf" {
                 r.inside_protobuf = Some(parse_bool(v)?);
             } else {
@@ -144,6 +155,7 @@ pub fn customize_from_rustproto_for_message(source: &MessageOptions) -> Customiz
     let serde_derive = rustproto::exts::serde_derive.get(source);
     let serde_derive_cfg = rustproto::exts::serde_derive_cfg.get(source);
     let lite_runtime = None;
+    let gen_mod_rs = None;
     let inside_protobuf = None;
     Customize {
         expose_oneof,
@@ -155,6 +167,7 @@ pub fn customize_from_rustproto_for_message(source: &MessageOptions) -> Customiz
         serde_derive,
         serde_derive_cfg,
         lite_runtime,
+        gen_mod_rs,
         inside_protobuf,
         _future_options: (),
     }
@@ -171,6 +184,7 @@ pub fn customize_from_rustproto_for_field(source: &FieldOptions) -> Customize {
     let serde_derive = None;
     let serde_derive_cfg = None;
     let lite_runtime = None;
+    let gen_mod_rs = None;
     let inside_protobuf = None;
     Customize {
         expose_oneof,
@@ -182,6 +196,7 @@ pub fn customize_from_rustproto_for_field(source: &FieldOptions) -> Customize {
         serde_derive,
         serde_derive_cfg,
         lite_runtime,
+        gen_mod_rs,
         inside_protobuf,
         _future_options: (),
     }
@@ -197,6 +212,7 @@ pub fn customize_from_rustproto_for_file(source: &FileOptions) -> Customize {
     let serde_derive = rustproto::exts::serde_derive_all.get(source);
     let serde_derive_cfg = rustproto::exts::serde_derive_cfg_all.get(source);
     let lite_runtime = rustproto::exts::lite_runtime_all.get(source);
+    let gen_mod_rs = None;
     let inside_protobuf = None;
     Customize {
         expose_oneof,
@@ -209,6 +225,7 @@ pub fn customize_from_rustproto_for_file(source: &FileOptions) -> Customize {
         serde_derive_cfg,
         lite_runtime,
         inside_protobuf,
+        gen_mod_rs,
         _future_options: (),
     }
 }

protobuf-codegen/src/lib.rs

@@ -53,7 +53,7 @@ pub use amend_io_error_util::amend_io_error;
 use scope::FileScope;
 use scope::RootScope;
 
-use crate::file::proto_path_to_fn_file_descriptor;
+use crate::file::{proto_path_to_fn_file_descriptor, proto_path_to_rust_mod};
 use inside::protobuf_crate_path;
 pub use protobuf_abs_path::ProtobufAbsolutePath;
 pub use protobuf_ident::ProtobufIdent;
@@ -243,13 +243,18 @@ impl FileIndex {
     }
 }
 
+struct GenFileResult {
+    compiler_plugin_result: compiler_plugin::GenResult,
+    mod_name: String,
+}
+
 fn gen_file(
     file_descriptor: &FileDescriptor,
     _files_map: &HashMap<&Path, &FileDescriptor>,
     root_scope: &RootScope,
     customize: &Customize,
     parser: &str,
-) -> compiler_plugin::GenResult {
+) -> GenFileResult {
     // TODO: use it
     let mut customize = customize.clone();
     // options specified in invocation have precedence over options specified in file
@@ -355,8 +360,26 @@ fn gen_file(
         }
     }
 
+    GenFileResult {
+        compiler_plugin_result: compiler_plugin::GenResult {
+            name: proto_name_to_rs(file_descriptor.proto().get_name()),
+            content: v,
+        },
+        mod_name: proto_path_to_rust_mod(file_descriptor.proto().get_name()).into_string(),
+    }
+}
+
+fn gen_mod_rs(mods: &[String]) -> compiler_plugin::GenResult {
+    let mut v = Vec::new();
+    let mut w = CodeWriter::new(&mut v);
+    w.comment("@generated");
+    w.write_line("");
+    for m in mods {
+        w.write_line(&format!("pub mod {};", m));
+    }
+    drop(w);
     compiler_plugin::GenResult {
-        name: proto_name_to_rs(file_descriptor.proto().get_name()),
+        name: "mod.rs".to_owned(),
         content: v,
     }
 }
@@ -382,19 +405,27 @@ pub fn gen(
         .map(|f| (Path::new(f.proto().get_name()), f))
         .collect();
 
+    let mut mods = Vec::new();
+
     for file_name in files_to_generate {
         let file = files_map.get(file_name.as_path()).expect(&format!(
             "file not found in file descriptors: {:?}, files: {:?}",
             file_name,
             files_map.keys()
         ));
-        results.push(gen_file(file, &files_map, &root_scope, customize, parser));
+        let gen_file_result = gen_file(file, &files_map, &root_scope, customize, parser);
+        results.push(gen_file_result.compiler_plugin_result);
+        mods.push(gen_file_result.mod_name);
     }
 
     if customize.inside_protobuf.unwrap_or(false) {
         results.push(gen_well_known_types_mod(&file_descriptors));
     }
 
+    if customize.gen_mod_rs.unwrap_or(false) {
+        results.push(gen_mod_rs(&mods));
+    }
+
     results
 }
 

protobuf-codegen/src/rust_name.rs

@@ -22,7 +22,7 @@ impl RustIdent {
         &self.0
     }
 
-    pub fn _into_string(self) -> String {
+    pub fn into_string(self) -> String {
         self.0
     }
 

protobuf-test/build.rs

@@ -7,10 +7,12 @@ extern crate protoc_rust;
 
 extern crate protobuf_test_common;
 
+use std::env;
 use std::fs;
 use std::io::Write;
 
 use protobuf_test_common::build::*;
+use std::path::Path;
 
 fn gen_in_dir(dir: &str, include_dir: &str) {
     gen_in_dir_impl(
@@ -71,10 +73,30 @@ fn generate_interop() {
         .unwrap();
 }
 
+fn generate_include_generated() {
+    let dir = format!("{}/include_generated", env::var("OUT_DIR").unwrap());
+    if Path::new(&dir).exists() {
+        fs::remove_dir_all(&dir).unwrap();
+    }
+    fs::create_dir(&dir).unwrap();
+    protoc_rust::Codegen::new()
+        .out_dir(dir)
+        .input("src/include_generated/v2.proto")
+        .input("src/include_generated/v3.proto")
+        .customize(Customize {
+            gen_mod_rs: Some(true),
+            ..Default::default()
+        })
+        .include("src/include_generated")
+        .run()
+        .unwrap();
+}
+
 fn generate_pb_rs() {
     generate_in_common();
     generate_in_v2_v3();
     generate_interop();
+    generate_include_generated();
 }
 
 fn main() {

protobuf-test/src/include_generated/mod.rs

@@ -0,0 +1,11 @@
+// Include single mod.rs which references two mods: `v2` and `v3`
+include!(concat!(env!("OUT_DIR"), "/include_generated/mod.rs"));
+
+use v2::V2Message;
+use v3::V3Message;
+
+#[test]
+fn test() {
+    let _ = V2Message::new();
+    let _ = V3Message::new();
+}

protobuf-test/src/include_generated/v2.proto

@@ -0,0 +1,3 @@
+syntax = "proto2";
+
+message V2Message {}

protobuf-test/src/include_generated/v3.proto

@@ -0,0 +1,8 @@
+syntax = "proto3";
+
+import "v2.proto";
+
+message V3Message {
+    // Test we can include other protos
+    V2Message v2 = 1;
+}

protobuf-test/src/lib.rs

@@ -28,3 +28,5 @@ mod common;
 mod google;
 
 mod interop;
+
+mod include_generated;