Get rid of error-chain in Linux DNS module

5 files changed, 90 insertions, 71 deletions

diff --git a/Cargo.lock b/Cargo.lock
index fc76a682b5..e4fac23be8 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -306,6 +306,17 @@ dependencies = [
 ]
 
 [[package]]
+name = "derive_more"
+version = "0.14.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "proc-macro2 0.4.27 (registry+https://github.com/rust-lang/crates.io-index)",
+ "quote 0.6.11 (registry+https://github.com/rust-lang/crates.io-index)",
+ "rustc_version 0.2.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "syn 0.15.29 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
 name = "digest"
 version = "0.8.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -1970,6 +1981,7 @@ version = "0.1.0"
 dependencies = [
  "atty 0.2.11 (registry+https://github.com/rust-lang/crates.io-index)",
  "dbus 0.6.4 (registry+https://github.com/rust-lang/crates.io-index)",
+ "derive_more 0.14.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "duct 0.12.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "err-derive 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "error-chain 0.12.0 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -2633,6 +2645,7 @@ dependencies = [
 "checksum derive-try-from-primitive 0.1.0 (registry+https://github.com/rust-lang/crates.io-index)" = "81dbd65eb15734b6d50dc6ac86f14f928462be0a5df6bda17761e909071ede5d"
 "checksum derive_builder 0.5.1 (registry+https://github.com/rust-lang/crates.io-index)" = "8c998e6ab02a828dd9735c18f154e14100e674ed08cb4e1938f0e4177543f439"
 "checksum derive_builder_core 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)" = "735e24ee9e5fa8e16b86da5007856e97d592e11867e45d76e0c0d0a164a0b757"
+"checksum derive_more 0.14.0 (registry+https://github.com/rust-lang/crates.io-index)" = "fbe9f11be34f800b3ecaaed0ec9ec2e015d1d0ba0c8644c1310f73d6e8994615"
 "checksum digest 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)" = "05f47366984d3ad862010e22c7ce81a7dbcaebbdfb37241a620f8b6596ee135c"
 "checksum dirs 1.0.5 (registry+https://github.com/rust-lang/crates.io-index)" = "3fd78930633bd1c6e35c4b42b1df7b0cbc6bc191146e512bb3bedf243fcc3901"
 "checksum duct 0.12.0 (registry+https://github.com/rust-lang/crates.io-index)" = "3640af123c78bedc20c1d3928e43cc0621e57011899d1ef917900c12fdb7a1ee"
diff --git a/talpid-core/Cargo.toml b/talpid-core/Cargo.toml
index d7116a7457..1d2e0f5276 100644
--- a/talpid-core/Cargo.toml
+++ b/talpid-core/Cargo.toml
@@ -8,6 +8,7 @@ edition = "2018"
 
 [dependencies]
 atty = "0.2"
+derive_more = "0.14"
 duct = "0.12"
 error-chain = "0.12"
 err-derive = "0.1.5"
diff --git a/talpid-core/src/dns/linux/mod.rs b/talpid-core/src/dns/linux/mod.rs
index 17ec6b7e39..5f378875f4 100644
--- a/talpid-core/src/dns/linux/mod.rs
+++ b/talpid-core/src/dns/linux/mod.rs
@@ -12,19 +12,30 @@ use std::{env, fmt, net::IpAddr, path::Path};
 
 const RESOLV_CONF_PATH: &str = "/etc/resolv.conf";
 
-error_chain! {
-    errors {
-        NoDnsMonitor {
-            description("No suitable DNS monitor implementation detected")
-        }
-    }
+pub type Result<T> = std::result::Result<T, Error>;
 
-    links {
-        Resolvconf(resolvconf::Error, resolvconf::ErrorKind);
-        StaticResolvConf(static_resolv_conf::Error, static_resolv_conf::ErrorKind);
-        SystemdResolved(systemd_resolved::Error, systemd_resolved::ErrorKind);
-        NetworkManager(network_manager::Error, network_manager::ErrorKind);
-    }
+/// Errors that can happen in the Linux DNS monitor
+#[derive(err_derive::Error, derive_more::From, Debug)]
+pub enum Error {
+    /// Error in systemd-resolved DNS monitor
+    #[error(display = "Error in systemd-resolved DNS monitor")]
+    SystemdResolved(#[error(cause)] systemd_resolved::Error),
+
+    /// Error in NetworkManager DNS monitor
+    #[error(display = "Error in NetworkManager DNS monitor")]
+    NetworkManager(#[error(cause)] network_manager::Error),
+
+    /// Error in resolvconf DNS monitor
+    #[error(display = "Error in resolvconf DNS monitor")]
+    Resolvconf(#[error(cause)] resolvconf::Error),
+
+    /// Error in static /etc/resolv.conf DNS monitor
+    #[error(display = "Error in static /etc/resolv.conf DNS monitor")]
+    StaticResolvConf(#[error(cause)] static_resolv_conf::Error),
+
+    /// No suitable DNS monitor implementation detected
+    #[error(display = "No suitable DNS monitor implementation detected")]
+    NoDnsMonitor,
 }
 
 pub struct DnsMonitor {
@@ -56,10 +67,10 @@ impl super::DnsMonitorT for DnsMonitor {
 }
 
 pub enum DnsMonitorHolder {
-    Resolvconf(Resolvconf),
-    StaticResolvConf(StaticResolvConf),
     SystemdResolved(SystemdResolved),
     NetworkManager(NetworkManager),
+    Resolvconf(Resolvconf),
+    StaticResolvConf(StaticResolvConf),
 }
 
 impl fmt::Display for DnsMonitorHolder {
@@ -96,7 +107,7 @@ impl DnsMonitorHolder {
             .or_else(|_| NetworkManager::new().map(DnsMonitorHolder::NetworkManager))
             .or_else(|_| Resolvconf::new().map(DnsMonitorHolder::Resolvconf))
             .or_else(|_| StaticResolvConf::new().map(DnsMonitorHolder::StaticResolvConf))
-            .chain_err(|| ErrorKind::NoDnsMonitor)
+            .map_err(|_| Error::NoDnsMonitor)
     }
 
     fn set(&mut self, interface: &str, servers: &[IpAddr]) -> Result<()> {
diff --git a/talpid-core/src/dns/linux/network_manager.rs b/talpid-core/src/dns/linux/network_manager.rs
index d42bb4efab..46777e8223 100644
--- a/talpid-core/src/dns/linux/network_manager.rs
+++ b/talpid-core/src/dns/linux/network_manager.rs
@@ -3,7 +3,6 @@ use dbus::{
     stdintf::*,
     BusType,
 };
-use error_chain::ChainedError;
 use std::{
     collections::HashMap,
     fs::File,
@@ -12,22 +11,21 @@ use std::{
     path::Path,
 };
 
-error_chain! {
-    errors {
-        NoNetworkManager {
-            description("NetworkManager not detected")
-        }
-        NmTooOld {
-            description("NetworkManager is too old")
-        }
-        NmNotManagingDns{
-            description("NetworkManager is not managing DNS")
-        }
-    }
+pub type Result<T> = std::result::Result<T, Error>;
 
-    foreign_links {
-        DbusError(dbus::Error);
-    }
+#[derive(err_derive::Error, Debug)]
+pub enum Error {
+    #[error(display = "NetworkManager not detected")]
+    NetworkManagerNotDetected(#[error(cause)] dbus::Error),
+
+    #[error(display = "NetworkManager is too old")]
+    TooOldNetworkManager(#[error(cause)] dbus::Error),
+
+    #[error(display = "NetworkManager is not managing DNS")]
+    NetworkManagerNotManagingDns,
+
+    #[error(display = "Error while communicating over Dbus")]
+    Dbus(#[error(cause)] dbus::Error),
 }
 
 const NM_BUS: &str = "org.freedesktop.NetworkManager";
@@ -46,7 +44,8 @@ pub struct NetworkManager {
 
 impl NetworkManager {
     pub fn new() -> Result<Self> {
-        let dbus_connection = dbus::Connection::get_private(BusType::System)?;
+        let dbus_connection =
+            dbus::Connection::get_private(BusType::System).map_err(Error::Dbus)?;
         let manager = NetworkManager { dbus_connection };
         manager.ensure_network_manager_exists()?;
         manager.ensure_resolv_conf_is_managed()?;
@@ -57,7 +56,7 @@ impl NetworkManager {
         let _: Box<RefArg> = self
             .as_manager()
             .get(&NM_TOP_OBJECT, GLOBAL_DNS_CONF_KEY)
-            .chain_err(|| ErrorKind::NoNetworkManager)?;
+            .map_err(Error::NetworkManagerNotDetected)?;
         Ok(())
     }
 
@@ -67,16 +66,13 @@ impl NetworkManager {
             .dbus_connection
             .with_path(NM_BUS, NM_DNS_MANAGER_PATH, RPC_TIMEOUT_MS)
             .get(NM_DNS_MANAGER, RC_MANAGEMENT_MODE_KEY)
-            .chain_err(|| ErrorKind::NmTooOld);
+            .map_err(Error::TooOldNetworkManager);
 
         match management_mode {
-            Err(e) => {
-                log::debug!("Failed to get NM management mode - {}", e.display_chain());
-                return Err(e);
-            }
+            Err(e) => return Err(e),
             Ok(management_mode) => {
                 if management_mode == "unmanaged" {
-                    return Err(Error::from(ErrorKind::NmNotManagingDns));
+                    return Err(Error::NetworkManagerNotManagingDns);
                 }
             }
         }
@@ -85,7 +81,7 @@ impl NetworkManager {
         let actual_resolv_conf = "/etc/resolv.conf";
         if !eq_file_content(&expected_resolv_conf, &actual_resolv_conf) {
             log::debug!("/etc/resolv.conf differs from reference resolv.conf, therefore NM is not managing DNS");
-            bail!(ErrorKind::NmNotManagingDns);
+            return Err(Error::NetworkManagerNotManagingDns);
         }
 
         Ok(())
@@ -103,7 +99,7 @@ impl NetworkManager {
     fn set_global_dns(&mut self, config: GlobalDnsConfig) -> Result<()> {
         self.as_manager()
             .set(NM_TOP_OBJECT, GLOBAL_DNS_CONF_KEY, config)
-            .map_err(|e| e.into())
+            .map_err(Error::Dbus)
     }
 
     pub fn reset(&mut self) -> Result<()> {
diff --git a/talpid-core/src/dns/linux/resolvconf.rs b/talpid-core/src/dns/linux/resolvconf.rs
index 32b8fcd6b9..14ce3107a1 100644
--- a/talpid-core/src/dns/linux/resolvconf.rs
+++ b/talpid-core/src/dns/linux/resolvconf.rs
@@ -1,31 +1,30 @@
 use std::{
     collections::HashSet,
     ffi::OsStr,
-    fs,
+    fs, io,
     net::IpAddr,
     path::{Path, PathBuf},
 };
 use which::which;
 
-error_chain! {
-    errors {
-        NoResolvconf {
-            description("Failed to detect 'resolvconf' program")
-        }
-        ResolvconfUsesResolved {
-            description("The existing resolvconf binary is just a symlink to systemd-resolved")
-        }
-        RunResolvconf {
-            description("Failed to execute 'resolvconf' program")
-        }
-        AddRecordError(stderr: String) {
-            description("Using 'resolvconf' to add a record failed")
-            display("Using 'resolvconf' to add a record failed: {}", stderr)
-        }
-        DeleteRecordError {
-            description("Using 'resolvconf' to delete a record failed")
-        }
-    }
+pub type Result<T> = std::result::Result<T, Error>;
+
+#[derive(err_derive::Error, Debug)]
+pub enum Error {
+    #[error(display = "Failed to detect 'resolvconf' program")]
+    NoResolvconf,
+
+    #[error(display = "The resolvconf in PATH is just a symlink to systemd-resolved")]
+    ResolvconfUsesResolved,
+
+    #[error(display = "Failed to execute 'resolvconf' program")]
+    RunResolvconf(#[error(cause)] io::Error),
+
+    #[error(display = "Using 'resolvconf' to add a record failed: {}", stderr)]
+    AddRecordError { stderr: String },
+
+    #[error(display = "Using 'resolvconf' to delete a record failed")]
+    DeleteRecordError,
 }
 
 pub struct Resolvconf {
@@ -35,10 +34,9 @@ pub struct Resolvconf {
 
 impl Resolvconf {
     pub fn new() -> Result<Self> {
-        let resolvconf_path =
-            which("resolvconf").map_err(|_| Error::from(ErrorKind::NoResolvconf))?;
+        let resolvconf_path = which("resolvconf").map_err(|_| Error::NoResolvconf)?;
         if Self::resolvconf_is_resolved_symlink(&resolvconf_path) {
-            bail!(ErrorKind::ResolvconfUsesResolved);
+            return Err(Error::ResolvconfUsesResolved);
         }
         Ok(Resolvconf {
             record_names: HashSet::new(),
@@ -69,12 +67,12 @@ impl Resolvconf {
             .stderr_capture()
             .unchecked()
             .run()
-            .chain_err(|| ErrorKind::RunResolvconf)?;
+            .map_err(Error::RunResolvconf)?;
 
-        ensure!(
-            output.status.success(),
-            ErrorKind::AddRecordError(String::from_utf8_lossy(&output.stderr).to_string())
-        );
+        if !output.status.success() {
+            let stderr = String::from_utf8_lossy(&output.stderr).to_string();
+            return Err(Error::AddRecordError { stderr });
+        }
 
         self.record_names.insert(record_name);
 
@@ -89,7 +87,7 @@ impl Resolvconf {
                 .stderr_capture()
                 .unchecked()
                 .run()
-                .chain_err(|| ErrorKind::RunResolvconf)?;
+                .map_err(Error::RunResolvconf)?;
 
             if !output.status.success() {
                 log::error!(
@@ -97,7 +95,7 @@ impl Resolvconf {
                     record_name,
                     String::from_utf8_lossy(&output.stderr)
                 );
-                result = Err(Error::from(ErrorKind::DeleteRecordError));
+                result = Err(Error::DeleteRecordError);
             }
         }