refactor(gui-client): improve error handling of Tauri commands (#9380)

Introducing a dedicated `Error` type allows us to directly serialise
`anyhow::Error`s to the GUI. Those will then be reported to Sentry on
the TS side.

rust/gui-client/src-tauri/src/view.rs

@@ -1,7 +1,8 @@
 use std::{path::PathBuf, time::Duration};
 
-use anyhow::{Context as _, Result, bail};
+use anyhow::Context as _;
 use firezone_logging::err_with_src;
+use serde::Serialize;
 use tauri::{Wry, ipc::Invoke};
 use tauri_plugin_dialog::DialogExt as _;
 
@@ -24,39 +25,34 @@ pub fn generate_handler() -> impl Fn(Invoke<Wry>) -> bool + Send + Sync + 'stati
 }
 
 #[tauri::command]
-async fn clear_logs(managed: tauri::State<'_, Managed>) -> Result<(), String> {
+async fn clear_logs(managed: tauri::State<'_, Managed>) -> Result<()> {
     let (tx, rx) = tokio::sync::oneshot::channel();
-    if let Err(error) = managed.ctlr_tx.send(ControllerRequest::ClearLogs(tx)).await {
-        // Tauri will only log errors to the JS console for us, so log this ourselves.
-        tracing::error!(
-            "Error while asking `Controller` to clear logs: {}",
-            err_with_src(&error)
-        );
-        return Err(error.to_string());
-    }
-    if let Err(error) = rx.await {
-        tracing::error!(
-            "Error while awaiting log-clearing operation: {}",
-            err_with_src(&error)
-        );
-        return Err(error.to_string());
-    }
+
+    managed
+        .ctlr_tx
+        .send(ControllerRequest::ClearLogs(tx))
+        .await
+        .context("Failed to send `ClearLogs` command")?;
+
+    rx.await
+        .context("Failed to await `ClearLogs` result")?
+        .map_err(anyhow::Error::msg)?;
+
     Ok(())
 }
 
 #[tauri::command]
-async fn export_logs(
-    app: tauri::AppHandle,
-    managed: tauri::State<'_, Managed>,
-) -> Result<(), String> {
-    show_export_dialog(&app, managed.ctlr_tx.clone()).map_err(|e| e.to_string())
+async fn export_logs(app: tauri::AppHandle, managed: tauri::State<'_, Managed>) -> Result<()> {
+    show_export_dialog(&app, managed.ctlr_tx.clone())?;
+
+    Ok(())
 }
 
 #[tauri::command]
 async fn apply_advanced_settings(
     managed: tauri::State<'_, Managed>,
     settings: AdvancedSettings,
-) -> Result<(), String> {
+) -> Result<()> {
     if managed.inner().inject_faults {
         tokio::time::sleep(Duration::from_secs(2)).await;
     }
@@ -65,13 +61,13 @@ async fn apply_advanced_settings(
         .ctlr_tx
         .send(ControllerRequest::ApplySettings(Box::new(settings)))
         .await
-        .map_err(|e| e.to_string())?;
+        .context("Failed to send `ApplySettings` command")?;
 
     Ok(())
 }
 
 #[tauri::command]
-async fn reset_advanced_settings(managed: tauri::State<'_, Managed>) -> Result<(), String> {
+async fn reset_advanced_settings(managed: tauri::State<'_, Managed>) -> Result<()> {
     apply_advanced_settings(managed, AdvancedSettings::default()).await?;
 
     Ok(())
@@ -83,9 +79,9 @@ fn show_export_dialog(app: &tauri::AppHandle, ctlr_tx: CtlrTx) -> Result<()> {
     let datetime_string = now.format("%Y_%m_%d-%H-%M");
     let stem = PathBuf::from(format!("firezone_logs_{datetime_string}"));
     let filename = stem.with_extension("zip");
-    let Some(filename) = filename.to_str() else {
-        bail!("zip filename isn't valid Unicode");
-    };
+    let filename = filename
+        .to_str()
+        .context("zip filename isn't valid Unicode")?;
 
     tauri_plugin_dialog::FileDialogBuilder::new(app.dialog().clone())
         .add_filter("Zip", &["zip"])
@@ -112,37 +108,54 @@ fn show_export_dialog(app: &tauri::AppHandle, ctlr_tx: CtlrTx) -> Result<()> {
 }
 
 #[tauri::command]
-async fn sign_in(managed: tauri::State<'_, Managed>) -> Result<(), String> {
+async fn sign_in(managed: tauri::State<'_, Managed>) -> Result<()> {
     managed
         .ctlr_tx
         .send(ControllerRequest::SignIn)
         .await
-        .context("Failed to send `SignIn` command")
-        .map_err(|e| e.to_string())?;
+        .context("Failed to send `SignIn` command")?;
 
     Ok(())
 }
 
 #[tauri::command]
-async fn sign_out(managed: tauri::State<'_, Managed>) -> Result<(), String> {
+async fn sign_out(managed: tauri::State<'_, Managed>) -> Result<()> {
     managed
         .ctlr_tx
         .send(ControllerRequest::SignOut)
         .await
-        .context("Failed to send `SignOut` command")
-        .map_err(|e| e.to_string())?;
+        .context("Failed to send `SignOut` command")?;
 
     Ok(())
 }
 
 #[tauri::command]
-async fn update_state(managed: tauri::State<'_, Managed>) -> Result<(), String> {
+async fn update_state(managed: tauri::State<'_, Managed>) -> Result<()> {
     managed
         .ctlr_tx
         .send(ControllerRequest::UpdateState)
         .await
-        .context("Failed to send `UpdateState` command")
-        .map_err(|e| e.to_string())?;
+        .context("Failed to send `UpdateState` command")?;
 
     Ok(())
 }
+
+type Result<T> = std::result::Result<T, Error>;
+
+#[derive(Debug)]
+struct Error(anyhow::Error);
+
+impl Serialize for Error {
+    fn serialize<S>(&self, serializer: S) -> std::result::Result<S::Ok, S::Error>
+    where
+        S: serde::Serializer,
+    {
+        serializer.serialize_str(&format!("{:#}", self.0))
+    }
+}
+
+impl From<anyhow::Error> for Error {
+    fn from(value: anyhow::Error) -> Self {
+        Self(value)
+    }
+}