plugin_mqtt: Improve error reporting

This patch improves the error handling story of the plugin_mqtt
by introducing a dedicated error type.

Signed-off-by: Matthias Beyer <matthias.beyer@ifm.com>

5 files changed, 27 insertions, 45 deletions

diff --git a/plugins/plugin_mqtt/Cargo.toml b/plugins/plugin_mqtt/Cargo.toml
index 43cbdc2e..2ce68c03 100644
--- a/plugins/plugin_mqtt/Cargo.toml
+++ b/plugins/plugin_mqtt/Cargo.toml
@@ -17,6 +17,7 @@ serde = { version = "1", features = ["derive"] }
 tokio = { version = "1", features = [] }
 tokio-util = "0.7.0"
 tracing = "0.1"
+toml = "0.5"
 
 tedge_api = { path = "../../crates/core/tedge_api" }
 tedge_lib = { path = "../../crates/core/tedge_lib" }
diff --git a/plugins/plugin_mqtt/src/builder.rs b/plugins/plugin_mqtt/src/builder.rs
index 748a1efa..05c5c4c3 100644
--- a/plugins/plugin_mqtt/src/builder.rs
+++ b/plugins/plugin_mqtt/src/builder.rs
@@ -43,7 +43,7 @@ where
             .clone()
             .try_into()
             .map(|_: MqttConfig| ())
-            .map_err(|_| miette::miette!("Failed to parse mqtt configuration"))
+            .map_err(crate::error::Error::ConfigParseFailed)
             .map_err(PluginError::from)
     }
 
@@ -55,7 +55,7 @@ where
     ) -> Result<BuiltPlugin, PluginError> {
         let config = config
             .try_into::<MqttConfig>()
-            .map_err(|_| miette::miette!("Failed to parse mqtt configuration"))?;
+            .map_err(crate::error::Error::ConfigParseFailed)?;
 
         let addr = plugin_dir.get_address_for(&config.target)?;
         Ok(MqttPlugin::new(config, addr).finish())
diff --git a/plugins/plugin_mqtt/src/error.rs b/plugins/plugin_mqtt/src/error.rs
index e5ef6a3a..b7bb8916 100644
--- a/plugins/plugin_mqtt/src/error.rs
+++ b/plugins/plugin_mqtt/src/error.rs
@@ -1,29 +1,18 @@
-use miette::Result;
-
 #[derive(Debug, miette::Diagnostic, thiserror::Error)]
-#[error("Error while shutting down MQTT Plugin")]
-pub struct MqttShutdownError {
-    #[related]
-    errs: Vec<miette::Error>
-}
+pub(crate) enum Error {
+    #[error("Failed to parse configuration")]
+    ConfigParseFailed(toml::de::Error),
 
-impl MqttShutdownError {
-    pub fn build_for(clientres: Result<()>, stopres: Result<()>) -> std::result::Result<(), Self> {
-        let mut errs = Vec::with_capacity(2);
-        if let Err(e) = clientres {
-            errs.push(e);
-        }
+    #[error("Failed to publish message")]
+    FailedToPublish(paho_mqtt::errors::Error),
 
-        if let Err(e) = stopres {
-            errs.push(e);
-        }
+    #[error("No client, cannot send messages")]
+    NoClient,
 
-        if errs.is_empty() {
-            Ok(())
-        } else {
-            Err(Self {
-                errs
-            })
-        }
-    }
+    #[error("Failed to stop MQTT mainloop")]
+    FailedToStopMqttMainloop,
+
+    #[error("Failed to disconnect MQTT client")]
+    FailedToDisconnectMqttClient(paho_mqtt::errors::Error),
 }
+
diff --git a/plugins/plugin_mqtt/src/message.rs b/plugins/plugin_mqtt/src/message.rs
index 17af6e68..f37de48b 100644
--- a/plugins/plugin_mqtt/src/message.rs
+++ b/plugins/plugin_mqtt/src/message.rs
@@ -39,7 +39,6 @@ impl tedge_api::plugin::Message for IncomingMessage {
 
 tedge_api::make_receiver_bundle!(pub struct MqttMessageReceiver(IncomingMessage));
 
-
 #[derive(Debug)]
 pub struct OutgoingMessage {
     pub(crate) payload: Vec<u8>,
@@ -65,5 +64,3 @@ impl OutgoingMessage {
 impl tedge_api::plugin::Message for OutgoingMessage {
     type Reply = tedge_api::message::NoReply; // for now
 }
-
-
diff --git a/plugins/plugin_mqtt/src/plugin.rs b/plugins/plugin_mqtt/src/plugin.rs
index cf3e480e..c54c1fdc 100644
--- a/plugins/plugin_mqtt/src/plugin.rs
+++ b/plugins/plugin_mqtt/src/plugin.rs
@@ -1,6 +1,5 @@
 use async_trait::async_trait;
 
-use miette::Context;
 use miette::IntoDiagnostic;
 use tedge_api::address::Address;
 use tedge_api::address::ReplySender;
@@ -80,26 +79,21 @@ impl Plugin for MqttPlugin {
         debug!("Shutting down mqtt plugin!");
 
         // try to shutdown internal mainloop
-        let stop_err = if let Some(stopper) = self.stopper.take() {
+        if let Some(stopper) = self.stopper.take() {
             stopper
                 .stop()
-                .map_err(|e| miette::miette!("Failed to stop MQTT mainloop: {:?}", e))
-        } else {
-            Ok(())
-        };
+                .map_err(|_| crate::error::Error::FailedToStopMqttMainloop)?;
+        }
 
         // try to shutdown mqtt client
-        let client_shutdown_err = if let Some(client) = self.client.take() {
+        if let Some(client) = self.client.take() {
             client
                 .disconnect(None)
                 .await
-                .map_err(|e| miette::miette!("Failed to disconnect MQTT client: {:?}", e))
-                .map(|_| ())
-        } else {
-            Ok(())
-        };
+                .map_err(|e| crate::error::Error::FailedToDisconnectMqttClient(e))?;
+        }
 
-        crate::error::MqttShutdownError::build_for(client_shutdown_err, stop_err).into_diagnostic()
+        Ok(())
     }
 }
 
@@ -193,12 +187,13 @@ impl Handle<OutgoingMessage> for MqttPlugin {
             client
                 .publish(msg)
                 .await
-                .into_diagnostic()
-                .context("Failed to publish message")?;
+                .map_err(crate::error::Error::FailedToPublish)
+                .into_diagnostic()?;
+
             debug!("Publishing message succeeded");
             Ok(())
         } else {
-            Err(miette::miette!("No client, cannot send messages"))?
+            return Err(crate::error::Error::NoClient).into_diagnostic();
         }
     }
 }