fix(transport): Propagate errors in tls_config instead of unwrap/panic (#385)

* Propagate errors in tls_config instead of unwrap

Ran into `tls_connector` failing and causing our app to panic and shutdown as it seems there wasn't any way to avoid panicking in `tls_config`.

So after talking to @LucioFranco briefly `tls_config` now returns a `Result` instead and propagates errors to the caller, where they can be handled.

* Fix compile warning when tls feature is disabled

tonic/src/transport/channel/endpoint.rs

@@ -155,11 +155,15 @@ impl Endpoint {
     /// Configures TLS for the endpoint.
     #[cfg(feature = "tls")]
     #[cfg_attr(docsrs, doc(cfg(feature = "tls")))]
-    pub fn tls_config(self, tls_config: ClientTlsConfig) -> Self {
-        Endpoint {
-            tls: Some(tls_config.tls_connector(self.uri.clone()).unwrap()),
+    pub fn tls_config(self, tls_config: ClientTlsConfig) -> Result<Self, Error> {
+        Ok(Endpoint {
+            tls: Some(
+                tls_config
+                    .tls_connector(self.uri.clone())
+                    .map_err(|e| Error::from_source(e))?,
+            ),
             ..self
-        }
+        })
     }
 
     /// Set the value of `TCP_NODELAY` option for accepted connections. Enabled by default.

tonic/src/transport/mod.rs

@@ -30,7 +30,7 @@
 //! let mut channel = Channel::from_static("https://example.com")
 //!     .tls_config(ClientTlsConfig::new()
 //!         .ca_certificate(Certificate::from_pem(&cert))
-//!         .domain_name("example.com".to_string()))
+//!         .domain_name("example.com".to_string()))?
 //!     .timeout(Duration::from_secs(5))
 //!     .rate_limit(5, Duration::from_secs(1))
 //!     .concurrency_limit(256)
@@ -74,7 +74,7 @@
 //!
 //! Server::builder()
 //!     .tls_config(ServerTlsConfig::new()
-//!         .identity(Identity::from_pem(&cert, &key)))
+//!         .identity(Identity::from_pem(&cert, &key)))?
 //!     .concurrency_limit_per_connection(256)
 //!     .add_service(my_svc)
 //!     .serve(addr)

tonic/src/transport/server/mod.rs

@@ -18,6 +18,9 @@ use incoming::TcpIncoming;
 #[cfg(feature = "tls")]
 pub(crate) use incoming::TlsStream;
 
+#[cfg(feature = "tls")]
+use crate::transport::Error;
+
 use super::service::{Or, Routes, ServerIo, ServiceBuilderExt};
 use crate::{body::BoxBody, request::ConnectionInfo};
 use futures_core::Stream;
@@ -97,11 +100,15 @@ impl Server {
     /// Configure TLS for this server.
     #[cfg(feature = "tls")]
     #[cfg_attr(docsrs, doc(cfg(feature = "tls")))]
-    pub fn tls_config(self, tls_config: ServerTlsConfig) -> Self {
-        Server {
-            tls: Some(tls_config.tls_acceptor().unwrap()),
+    pub fn tls_config(self, tls_config: ServerTlsConfig) -> Result<Self, Error> {
+        Ok(Server {
+            tls: Some(
+                tls_config
+                    .tls_acceptor()
+                    .map_err(|e| Error::from_source(e))?,
+            ),
             ..self
-        }
+        })
     }
 
     /// Set the concurrency limit applied to on requests inbound per connection.