feat(client): add HttpConnector.enforce_http

This will make the `HttpConnector` require the `scheme` to be `http`,
and return an error otherwise. This value is enabled by default, so any
requests to URLs that aren't of scheme `http` will now see an error
message stating the failure.

When constructing a connector that wraps an `HttpConnector`, this
enforcement can be disabled to allow connecting over TCP easily even
when the scheme is not `http`. To do, call
`connector.enforce_http(false)`.

src/client/connect.rs

@@ -1,3 +1,4 @@
+use std::error::Error as StdError;
 use std::fmt;
 use std::io;
 //use std::net::SocketAddr;
@@ -42,6 +43,7 @@ where T: Service<Request=Uri, Error=io::Error> + 'static,
 #[derive(Clone)]
 pub struct HttpConnector {
     dns: dns::Dns,
+    enforce_http: bool,
     handle: Handle,
 }
 
@@ -50,15 +52,26 @@ impl HttpConnector {
     /// Construct a new HttpConnector.
     ///
     /// Takes number of DNS worker threads.
+    #[inline]
     pub fn new(threads: usize, handle: &Handle) -> HttpConnector {
         HttpConnector {
             dns: dns::Dns::new(threads),
+            enforce_http: true,
             handle: handle.clone(),
         }
     }
+
+    /// Option to enforce all `Uri`s have the `http` scheme.
+    ///
+    /// Enabled by default.
+    #[inline]
+    pub fn enforce_http(&mut self, is_enforced: bool) {
+        self.enforce_http = is_enforced;
+    }
 }
 
 impl fmt::Debug for HttpConnector {
+    #[inline]
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         f.debug_struct("HttpConnector")
             .finish()
@@ -73,12 +86,18 @@ impl Service for HttpConnector {
 
     fn call(&self, uri: Uri) -> Self::Future {
         debug!("Http::connect({:?})", uri);
+
+        if self.enforce_http {
+            if uri.scheme() != Some("http") {
+                return invalid_url(InvalidUrl::NotHttp, &self.handle);
+            }
+        } else if uri.scheme().is_none() {
+            return invalid_url(InvalidUrl::MissingScheme, &self.handle);
+        }
+
         let host = match uri.host() {
             Some(s) => s,
-            None => return HttpConnecting {
-                state: State::Error(Some(io::Error::new(io::ErrorKind::InvalidInput, "invalid url"))),
-                handle: self.handle.clone(),
-            },
+            None => return invalid_url(InvalidUrl::MissingAuthority, &self.handle),
         };
         let port = match uri.port() {
             Some(port) => port,
@@ -94,7 +113,37 @@ impl Service for HttpConnector {
             handle: self.handle.clone(),
         }
     }
+}
 
+#[inline]
+fn invalid_url(err: InvalidUrl, handle: &Handle) -> HttpConnecting {
+    HttpConnecting {
+        state: State::Error(Some(io::Error::new(io::ErrorKind::InvalidInput, err))),
+        handle: handle.clone(),
+    }
+}
+
+#[derive(Debug, Clone, Copy)]
+enum InvalidUrl {
+    MissingScheme,
+    NotHttp,
+    MissingAuthority,
+}
+
+impl fmt::Display for InvalidUrl {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.write_str(self.description())
+    }
+}
+
+impl StdError for InvalidUrl {
+    fn description(&self) -> &str {
+        match *self {
+            InvalidUrl::MissingScheme => "invalid URL, missing scheme",
+            InvalidUrl::NotHttp => "invalid URL, scheme must be http",
+            InvalidUrl::MissingAuthority => "invalid URL, missing domain",
+        }
+    }
 }
 
 /// A Future representing work to connect to a URL.
@@ -195,7 +244,7 @@ mod tests {
     use super::{Connect, HttpConnector};
 
     #[test]
-    fn test_non_http_url() {
+    fn test_errors_missing_authority() {
         let mut core = Core::new().unwrap();
         let url = "/foo/bar?baz".parse().unwrap();
         let connector = HttpConnector::new(1, &core.handle());
@@ -203,4 +252,22 @@ mod tests {
         assert_eq!(core.run(connector.connect(url)).unwrap_err().kind(), io::ErrorKind::InvalidInput);
     }
 
+    #[test]
+    fn test_errors_enforce_http() {
+        let mut core = Core::new().unwrap();
+        let url = "https://example.domain/foo/bar?baz".parse().unwrap();
+        let connector = HttpConnector::new(1, &core.handle());
+
+        assert_eq!(core.run(connector.connect(url)).unwrap_err().kind(), io::ErrorKind::InvalidInput);
+    }
+
+
+    #[test]
+    fn test_errors_missing_scheme() {
+        let mut core = Core::new().unwrap();
+        let url = "example.domain".parse().unwrap();
+        let connector = HttpConnector::new(1, &core.handle());
+
+        assert_eq!(core.run(connector.connect(url)).unwrap_err().kind(), io::ErrorKind::InvalidInput);
+    }
 }