Derive IPC interface only when ipc feature is on (#2463)

* derive -> ipc

* accident repair

* conditional ipc deriving

* fix test

ipc/codegen/src/lib.rs

@@ -56,7 +56,7 @@ pub fn expand(src: &std::path::Path, dst: &std::path::Path) {
 }
 
 #[cfg(feature = "with-syntex")]
-pub fn register(reg: &mut syntex::Registry) {
+pub fn register_cleaner(reg: &mut syntex::Registry) {
 	use syntax::{ast, fold};
 
 	#[cfg(feature = "with-syntex")]
@@ -66,6 +66,7 @@ pub fn register(reg: &mut syntex::Registry) {
 			fn fold_attribute(&mut self, attr: ast::Attribute) -> Option<ast::Attribute> {
 				match attr.node.value.node {
 					ast::MetaItemKind::List(ref n, _) if n == &"ipc" => { return None; }
+					ast::MetaItemKind::Word(ref n) if n == &"ipc" => { return None; }
 					_ => {}
 				}
 
@@ -80,13 +81,18 @@ pub fn register(reg: &mut syntex::Registry) {
 		fold::Folder::fold_crate(&mut StripAttributeFolder, krate)
 	}
 
+	reg.add_post_expansion_pass(strip_attributes);
+}
+
+#[cfg(feature = "with-syntex")]
+pub fn register(reg: &mut syntex::Registry) {
 	reg.add_attr("feature(custom_derive)");
 	reg.add_attr("feature(custom_attribute)");
 
 	reg.add_decorator("ipc", codegen::expand_ipc_implementation);
 	reg.add_decorator("derive_Binary", serialization::expand_serialization_implementation);
 
-	reg.add_post_expansion_pass(strip_attributes);
+	register_cleaner(reg);
 }
 
 #[cfg(not(feature = "with-syntex"))]
@@ -104,7 +110,34 @@ pub fn register(reg: &mut rustc_plugin::Registry) {
 }
 
 #[derive(Debug)]
-pub enum Error { InvalidFileName, ExpandFailure }
+pub enum Error { InvalidFileName, ExpandFailure, Io(std::io::Error) }
+
+impl std::convert::From<std::io::Error> for Error {
+	fn from(err: std::io::Error) -> Self {
+		Error::Io(err)
+	}
+}
+
+pub fn derive_ipc_cond(src_path: &str, has_feature: bool) -> Result<(), Error> {
+	if has_feature { derive_ipc(src_path) }
+	else { cleanup_ipc(src_path) }
+}
+
+pub fn cleanup_ipc(src_path: &str) -> Result<(), Error> {
+	use std::env;
+	use std::path::{Path, PathBuf};
+
+	let out_dir = env::var_os("OUT_DIR").unwrap();
+	let file_name = try!(PathBuf::from(src_path).file_name().ok_or(Error::InvalidFileName).map(|val| val.to_str().unwrap().to_owned()));
+	let mut registry = syntex::Registry::new();
+	register_cleaner(&mut registry);
+	if let Err(_) = registry.expand("", &Path::new(src_path), &Path::new(&out_dir).join(&file_name))
+	{
+		// will be reported by compiler
+		return Err(Error::ExpandFailure)
+	}
+	Ok(())
+}
 
 pub fn derive_ipc(src_path: &str) -> Result<(), Error> {
 	use std::env;
@@ -113,11 +146,11 @@ pub fn derive_ipc(src_path: &str) -> Result<(), Error> {
 	let out_dir = env::var_os("OUT_DIR").unwrap();
 	let file_name = try!(PathBuf::from(src_path).file_name().ok_or(Error::InvalidFileName).map(|val| val.to_str().unwrap().to_owned()));
 
+	let final_path = Path::new(&out_dir).join(&file_name);
+
 	let mut intermediate_file_name = file_name.clone();
 	intermediate_file_name.push_str(".rpc.in");
-
 	let intermediate_path = Path::new(&out_dir).join(&intermediate_file_name);
-	let final_path = Path::new(&out_dir).join(&file_name);
 
 	{
 		let mut registry = syntex::Registry::new();