Add support for system/environment proxies (#547)

tests/proxy.rs

@@ -3,6 +3,8 @@ extern crate reqwest;
 #[macro_use]
 mod support;
 
+use std::env;
+
 #[test]
 fn http_proxy() {
     let server = server! {
@@ -115,3 +117,83 @@ fn http_proxy_basic_auth_parsed() {
     assert_eq!(res.status(), reqwest::StatusCode::OK);
     assert_eq!(res.headers().get(reqwest::header::SERVER).unwrap(), &"proxied");
 }
+
+#[test]
+fn test_no_proxy() {
+    let server = server! {
+        request: b"\
+            GET /4 HTTP/1.1\r\n\
+            user-agent: $USERAGENT\r\n\
+            accept: */*\r\n\
+            accept-encoding: gzip\r\n\
+            host: $HOST\r\n\
+            \r\n\
+            ",
+        response: b"\
+            HTTP/1.1 200 OK\r\n\
+            Server: test\r\n\
+            Content-Length: 0\r\n\
+            \r\n\
+            "
+    };
+    let proxy = format!("http://{}", server.addr());
+    let url = format!("http://{}/4", server.addr());
+
+    // set up proxy and use no_proxy to clear up client builder proxies.
+    let res = reqwest::Client::builder()
+        .proxy(
+            reqwest::Proxy::http(&proxy).unwrap()
+        )
+        .no_proxy()
+        .build()
+        .unwrap()
+        .get(&url)
+        .send()
+        .unwrap();
+
+    assert_eq!(res.url().as_str(), &url);
+    assert_eq!(res.status(), reqwest::StatusCode::OK);
+}
+
+#[test]
+fn test_using_system_proxy() {
+    let server = server! {
+        request: b"\
+            GET http://hyper.rs/prox HTTP/1.1\r\n\
+            user-agent: $USERAGENT\r\n\
+            accept: */*\r\n\
+            accept-encoding: gzip\r\n\
+            host: hyper.rs\r\n\
+            \r\n\
+            ",
+        response: b"\
+            HTTP/1.1 200 OK\r\n\
+            Server: proxied\r\n\
+            Content-Length: 0\r\n\
+            \r\n\
+            "
+    };
+    // save system setting first.
+    let system_proxy = env::var("http_proxy");
+    // set-up http proxy.
+    env::set_var("http_proxy", format!("http://{}", server.addr()));
+
+    let url = "http://hyper.rs/prox";
+    let res = reqwest::Client::builder()
+        .use_sys_proxy()
+        .build()
+        .unwrap()
+        .get(url)
+        .send()
+        .unwrap();
+
+    assert_eq!(res.url().as_str(), url);
+    assert_eq!(res.status(), reqwest::StatusCode::OK);
+    assert_eq!(res.headers().get(reqwest::header::SERVER).unwrap(), &"proxied");
+
+    // reset user setting.
+    match system_proxy {
+        Err(_) => env::remove_var("http_proxy"),
+        Ok(proxy) => env::set_var("http_proxy", proxy)
+    }
+}