feat(transport): Make serde optionnal

lettre/Cargo.toml

@@ -21,12 +21,15 @@ native-tls = "^0.1"
 base64 = "^0.6"
 hex = "^0.2"
 rust-crypto = "^0.2"
-serde = "^1.0"
-serde_json = "^1.0"
-serde_derive = "^1.0"
+serde = { version = "^1.0", optional = true }
+serde_json = { version = "^1.0", optional = true }
+serde_derive = { version = "^1.0", optional = true }
 
 [dev-dependencies]
 env_logger = "^0.4"
 
 [features]
+default = ["file-transport"]
 unstable = []
+serde-impls = ["serde", "serde_derive"]
+file-transport = ["serde-impls", "serde_json"]

lettre/src/lib.rs

@@ -13,20 +13,25 @@ extern crate hex;
 extern crate crypto;
 extern crate bufstream;
 extern crate native_tls;
+#[cfg(feature = "file-transport")]
 extern crate serde_json;
+#[cfg(feature = "serde-impls")]
 extern crate serde;
+#[cfg(feature = "serde-impls")]
 #[macro_use]
 extern crate serde_derive;
 
 pub mod smtp;
 pub mod sendmail;
 pub mod stub;
+#[cfg(feature = "file-transport")]
 pub mod file;
 use std::fmt;
 use std::fmt::{Display, Formatter};
 
 /// Email address
-#[derive(PartialEq, Eq, Clone, Debug, Serialize, Deserialize)]
+#[derive(PartialEq, Eq, Clone, Debug)]
+#[cfg_attr(feature = "serde-impls", derive(Serialize, Deserialize))]
 pub struct EmailAddress(pub String);
 
 impl Display for EmailAddress {
@@ -63,7 +68,8 @@ pub trait EmailTransport<U> {
 }
 
 /// Minimal email structure
-#[derive(Debug, Clone, Serialize, Deserialize)]
+#[derive(Debug, Clone)]
+#[cfg_attr(feature = "serde-impls", derive(Serialize, Deserialize))]
 pub struct SimpleSendableEmail {
     /// To
     to: Vec<EmailAddress>,

lettre/tests/lib.rs

@@ -3,4 +3,5 @@ extern crate lettre;
 mod transport_smtp;
 mod transport_sendmail;
 mod transport_stub;
+#[cfg(feature = "file-transport")]
 mod transport_file;

lettre/tests/transport_file.rs

@@ -1,7 +1,7 @@
 extern crate lettre;
 
 use lettre::{EmailAddress, EmailTransport, SendableEmail, SimpleSendableEmail};
-
+#[cfg(feature = "file-transport")]
 use lettre::file::FileEmailTransport;
 use std::env::temp_dir;
 use std::fs::File;
@@ -9,6 +9,7 @@ use std::fs::remove_file;
 use std::io::Read;
 
 #[test]
+#[cfg(feature = "file-transport")]
 fn file_transport() {
     let mut sender = FileEmailTransport::new(temp_dir());
     let email = SimpleSendableEmail::new(